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Neurocognitive Performance and Prior Injury Among U.S. Department of Defense Military Personnel

Neurocognitive Performance and Prior Injury Among U.S. Department of Defense Military Personnel ABSTRACT This study examined the neurocognitive performance of U.S. military personnel completing the Automated Neuropsychological Assessment Metrics (version 4) TBI Military (ANAM4 TBI-MIL) battery as part of the Department of Defense Neurocognitive Functional Assessment Program. Descriptive analyses utilizing the ANAM4TBI Military Performance Database were performed. We examined ANAM Composite Score (ACS) differences between five injury subgroups (no injury, brain injury with current symptoms, brain injury without current symptoms, nonbrain injury with current symptoms, and nonbrain injury without current symptoms) using general linear mixed modeling. Almost 11% (70,472/641,285) reported brain injury in the 4 years before assessment. The ACS differed significantly by injury group (p < 0.0001). In comparison to the no injury group, those reporting brain injury with current symptoms (d = −0.44) and nonbrain injury with current symptoms (d = −0.24) demonstrated significantly reduced ACS scores (p < 0.0001) indicative of reduced neurocognitive proficiency. In this population-based study of U.S. military personnel, neurocognitive performance was significantly associated with reported injury within the past 4 years among those experiencing current symptoms. Occupational programs focusing on prospective brain health of injured population groups are warranted. INTRODUCTION The prospective cognitive and neurological health of military personnel1 is of considerable concern, in light of the heightened awareness of the health consequences of traumatic brain injury (TBI) events and other experiences occurring in operational and training environments.2,3 Additionally, the publicity surrounding the high rate of sports-related head injury in high school, collegiate, and professional athletes has served to illuminate and drive research efforts to better understand the long-term effects of brain injury on health and performance.4 Computer-based cognitive testing programs have been employed as a tool to screen for injury-related changes in cognitive status.5,6 In 2008, a Congressionally mandated program was established requiring all Department of Defense (DoD) service members deploying to Iraq or Afghanistan to complete a computer-based neurocognitive assessment.7 To comply with DoD's clinical testing policy,8 the Neurocognitive Functional Assessment Program was initiated, which established baseline neurocognitive status of all U.S. service members within 12 months before deployment using the Automated Neuropsychological Assessment Metrics (ANAM; version 4) TBI Military (ANAM4 TBI-MIL) battery. The ANAM4 TBI-MIL is a computer-based set of tests designed to measure cognitive performance across several functional domains, including executive functioning, attention, memory, response time, and information processing speed (Center for the Study of Human Operator Performance ANAM4. TBI-MIL: User Manual. Norman, Oklahoma: Center for the Study of Human Operator Performance; University of Oklahoma, 2007). Previous studies have documented the psychometric properties of ANAM tests9,–11 and normative data for military personnel12 have been provided. ANAM tests have been shown to be sensitive to the effects of mild brain injury,13,–16 especially in the acute phases17,–19 following injury. More recently, the ANAM test battery has been demonstrated to validly detect impairments in a mixed clinical patient sample.20 For this project, we integrated the ANAM4 TBI-MIL data into an analytical database (ANAM4TBI Military Performance Database, AMP-D) to examine neurocognitive performance metrics and factors that may influence performance. Given the emerging focus of brain health as a public health issue worldwide in both military and civilian populations (e.g., Army Performance Triad, The Brain Research through Advancing Innovative Neurotechnologies Initiative, European Year of the Brain21,–23), knowledge and understanding of the role that particular factors, especially modifiable ones, play in neurocognitive performance is a critical requirement from which appropriate prevention, training, intervention, and treatment programs can be launched. In this report, we used the AMP-D to examine neurocognitive performance and mood state profiles of DoD personnel completing the ANAM4 TBI-MIL. We compared performance and mood among military personnel who reported having brain or nonbrain injuries in the 4 years before their first ANAM4 TBI-MIL assessment and those reporting no injury. We predicted that having experienced an injury within the past 4 years, particularly where symptoms persist, is associated with reduced neurocognitive proficiency and adverse mood states. METHODS The study protocol was reviewed and approved by the Institutional Review Board at the U.S. Army Research Institute of Environmental Medicine and complied with all institutional guidelines for the protection of human subjects. Study Population The study population included all U.S. military personnel (n = 671,435) who were administered the ANAM4 TBI-MIL battery starting in 2007 through December 2010 as part of the mandated clinical testing policy.7,8,24 Procedures The ANAM4 TBI-MIL is a battery of tests administered via laptop computer, which takes approximately 20 minutes to complete (Table I). ANAM4 TBI-MIL incorporates two questionnaires requesting demographic and injury information (Demographics, TBI Questionnaire), two questionnaires requiring self-assessment of current state of arousal and mood (Sleepiness Scale [SLP], Mood Scale [MOO]), and seven performance tests (Simple Reaction Time [SRT], Code Substitution-Learning [CDS], Procedural Reaction Time [PRO], Mathematical Processing [MTH], Matching to Sample [M2S], Code Substitution-Delayed [CDD], and Simple Reaction Time Repeated [SR2]). More detailed descriptions of these tests have been provided elsewhere.9,12,25 TABLE I. ANAM4 TBI-MIL Battery and Functional Domains Assessed Task List  Task Abbreviation  Task Description/Functional Domains  Task Parameters Examined  TBI Questionnaire  TBQ  Report of TBI/Other Injury in Past 4 years and Past and Current Symptomatology  Injury Event Type and Related Health Symptoms  Sleepiness Scale  SLP  Assessment of Current Level of Sleepiness  Response Options are Ratings 1–7  Mood Scale  MOO  Assessment of Current Mood State in 7 Categories (7 Subscales: Vigor, Happiness, Depression, Anger, Fatigue, Anxiety, and Restlessness)  Mean of the Adjective Scores for Each Subscale  Simple Reaction Time  SRT  Basic Neural Processing (Motor Activity Speed/Efficiency)  Mean RT, % Correct, Throughput  Code Substitution Learning  CDS  Associative Learning (Speed/Efficiency)  Mean RT, % Correct, Throughput  Procedural Reaction Time  PRO  Processing Speed (Choice Reaction Time Rule Adherence)  Mean RT, % Correct, Throughput  Mathematical Processing  MTH  Working Memory  Mean RT, % Correct, Throughput  Matching to Sample  M2S  Visual Spatial Memory  Mean RT, % Correct, Throughput  Code Substitution-Delayed  CDD  Memory (Delayed)  Mean RT, % Correct, Throughput  Simple Reaction Time (R)  SR2  Basic Neural Processing (Motor Activity Speed /Efficiency)  Mean RT, % Correct, Throughput  Task List  Task Abbreviation  Task Description/Functional Domains  Task Parameters Examined  TBI Questionnaire  TBQ  Report of TBI/Other Injury in Past 4 years and Past and Current Symptomatology  Injury Event Type and Related Health Symptoms  Sleepiness Scale  SLP  Assessment of Current Level of Sleepiness  Response Options are Ratings 1–7  Mood Scale  MOO  Assessment of Current Mood State in 7 Categories (7 Subscales: Vigor, Happiness, Depression, Anger, Fatigue, Anxiety, and Restlessness)  Mean of the Adjective Scores for Each Subscale  Simple Reaction Time  SRT  Basic Neural Processing (Motor Activity Speed/Efficiency)  Mean RT, % Correct, Throughput  Code Substitution Learning  CDS  Associative Learning (Speed/Efficiency)  Mean RT, % Correct, Throughput  Procedural Reaction Time  PRO  Processing Speed (Choice Reaction Time Rule Adherence)  Mean RT, % Correct, Throughput  Mathematical Processing  MTH  Working Memory  Mean RT, % Correct, Throughput  Matching to Sample  M2S  Visual Spatial Memory  Mean RT, % Correct, Throughput  Code Substitution-Delayed  CDD  Memory (Delayed)  Mean RT, % Correct, Throughput  Simple Reaction Time (R)  SR2  Basic Neural Processing (Motor Activity Speed /Efficiency)  Mean RT, % Correct, Throughput  (R), Task was repeated at the end of the battery administration to provide a measure of response variation, an indicator of fatigue over the administration time period. RT, Response Time. View Large TABLE I. ANAM4 TBI-MIL Battery and Functional Domains Assessed Task List  Task Abbreviation  Task Description/Functional Domains  Task Parameters Examined  TBI Questionnaire  TBQ  Report of TBI/Other Injury in Past 4 years and Past and Current Symptomatology  Injury Event Type and Related Health Symptoms  Sleepiness Scale  SLP  Assessment of Current Level of Sleepiness  Response Options are Ratings 1–7  Mood Scale  MOO  Assessment of Current Mood State in 7 Categories (7 Subscales: Vigor, Happiness, Depression, Anger, Fatigue, Anxiety, and Restlessness)  Mean of the Adjective Scores for Each Subscale  Simple Reaction Time  SRT  Basic Neural Processing (Motor Activity Speed/Efficiency)  Mean RT, % Correct, Throughput  Code Substitution Learning  CDS  Associative Learning (Speed/Efficiency)  Mean RT, % Correct, Throughput  Procedural Reaction Time  PRO  Processing Speed (Choice Reaction Time Rule Adherence)  Mean RT, % Correct, Throughput  Mathematical Processing  MTH  Working Memory  Mean RT, % Correct, Throughput  Matching to Sample  M2S  Visual Spatial Memory  Mean RT, % Correct, Throughput  Code Substitution-Delayed  CDD  Memory (Delayed)  Mean RT, % Correct, Throughput  Simple Reaction Time (R)  SR2  Basic Neural Processing (Motor Activity Speed /Efficiency)  Mean RT, % Correct, Throughput  Task List  Task Abbreviation  Task Description/Functional Domains  Task Parameters Examined  TBI Questionnaire  TBQ  Report of TBI/Other Injury in Past 4 years and Past and Current Symptomatology  Injury Event Type and Related Health Symptoms  Sleepiness Scale  SLP  Assessment of Current Level of Sleepiness  Response Options are Ratings 1–7  Mood Scale  MOO  Assessment of Current Mood State in 7 Categories (7 Subscales: Vigor, Happiness, Depression, Anger, Fatigue, Anxiety, and Restlessness)  Mean of the Adjective Scores for Each Subscale  Simple Reaction Time  SRT  Basic Neural Processing (Motor Activity Speed/Efficiency)  Mean RT, % Correct, Throughput  Code Substitution Learning  CDS  Associative Learning (Speed/Efficiency)  Mean RT, % Correct, Throughput  Procedural Reaction Time  PRO  Processing Speed (Choice Reaction Time Rule Adherence)  Mean RT, % Correct, Throughput  Mathematical Processing  MTH  Working Memory  Mean RT, % Correct, Throughput  Matching to Sample  M2S  Visual Spatial Memory  Mean RT, % Correct, Throughput  Code Substitution-Delayed  CDD  Memory (Delayed)  Mean RT, % Correct, Throughput  Simple Reaction Time (R)  SR2  Basic Neural Processing (Motor Activity Speed /Efficiency)  Mean RT, % Correct, Throughput  (R), Task was repeated at the end of the battery administration to provide a measure of response variation, an indicator of fatigue over the administration time period. RT, Response Time. View Large Under the DoD-mandated clinical testing program, ANAM4 TBI-MIL administration was conducted in a standardized manner by trained test proctors at designated sites. The battery was administered primarily in groups, during the daytime hours, in a quiet room. All except two test modules (CDD, SR2) began with practice items to assist in learning the procedures and instructions before the actual test data collection occurred. If a participant did not understand the instructions, test proctors were present to provide clarification and answer questions. Per field operational procedures, data for each test were screened upon completion for potentially invalid test performance (defined as accuracy scores less than or equal to 56%), which could indicate potential misunderstanding of directions or poor effort. Individuals with test performances falling below these accuracy criteria were provided with clarification of the test instructions and asked to repeat that given test. Individual data files of ANAM4 TBI-MIL assessments were obtained from the ANAM Program Office (Neurocognitive Assessment Branch), U.S. Army Office of the Surgeon General. Military service and deployment history data, as well as other demographic (e.g., age, education level, sex, race) and military service (rank, service branch, component, and occupation) information were requested and provided by the Defense Manpower Data Center (DMDC) for use in this project through approved research processes. These data sources were integrated to form the master database (AMP-D) housed and managed at U.S. Army Research Institute of Environmental Medicine. Data Analyses In this report, we examined the data from 641,285 individuals administered the ANAM4 TBI-MIL as part of the standard predeployment procedures. This subset includes those individuals 18 to 65 years of age who completed the TBI questionnaire module and at least the SRT test (the first test in the battery) with higher than 56% recorded task accuracy on the first administration (or second in the case of retest) administration and for whom pertinent DMDC personnel data were available. (Exclusions included: 79 due to missing linkage identifiers; 27,686 because they completed the battery for some other reason [such as for a clinical evaluation or postinjury assessment]; 18 who did not complete the TBI questionnaire module; 579 who did not meet SRT task accuracy criteria; and 1,798 because they were missing pertinent DMDC demographic information.) For those individuals who completed ANAM4 TBI-MIL more than once during this period due to multiple deployments between 2007 and 2010 (n = 73,702), only data from the first assessment date were included (Fig. 1). FIGURE 1. View largeDownload slide Flowchart diagram. FIGURE 1. View largeDownload slide Flowchart diagram. In addition to the SRT test, all other ANAM4 TBI-MIL performance tests (CDS, M2S, PRO, MTH, CDD, and SR2) were evaluated to determine whether each was completed with greater than 56% accuracy on the first or second test administration within the same calendar day, therefore satisfying test-specific field retest criteria. If a person did not meet the test-specific retest criteria or if test data were missing, their data for that test were not included in the analyses. The percentage of persons excluded by task was as follows: CDS, 0.04%; PRO, 0.15%; MTH, 0.28%; M2S, 0.49%; CDD, 1.35%; and SR2, 0.06%. The mean, median, and range values for all test-specific scores were computed. Mean response time (mean RT) for correct responses, percentage correct (% correct), and throughput (TP) (correct responses per minute of available response time) were the test parameters selected for analyses of the performance tasks. TP represents a combination of reaction time and accuracy.26 The Sleepiness Scale responses represent a current rating of sleepiness with possible scores ranging from 1 to 7 (higher number indicates greater sleepiness). For each of the seven Mood subscales, six adjectives are presented along with a response set ranging from “not at all” to “very much” (on a 0 to 6 point scale). The mean of the adjective responses for each of the seven Mood subscales was selected for analysis. Higher values indicate greater endorsement of the mood state dimension. To provide a measure of overall performance on the ANAM4 TBI-MIL cognitive tests, the ANAM composite score (ACS) was computed by converting TP scores for all tasks in the battery to T-scores relative to an age- and gender-matched normative group.12,25,27 The ACS is reported in standard deviation units with more negative values indicating poorer overall performance. In addition, the ANAM4 Performance Validity Index (PVI) was computed for each individual. The PVI provides an assessment of valid responding and is computed utilizing the accuracy and RT discrepancy scores from four ANAM4 TBI-MIL tasks: M2S, SRT, PRO, and CDS.28 The PVI total score ranges from 0 to 48 with higher scores indicating greater likelihood of atypical performance effort. In this report, the recommended cut point score of 10, representing a minimum of 90% specificity in an outpatient sample,28 was selected as an indicator of questionable performance effort. Pearson and point biserial correlation coefficients were computed to examine the relationship between TP and age, sex, and education level. To evaluate whether reporting an injury was associated with reduced cognitive proficiency or adverse mood, individuals were categorized into five injury subgroups (no injury, brain injury with current symptoms, brain injury with no current symptoms, nonbrain injury with current symptoms, and nonbrain injury with no current symptoms) based on their responses on the ANAM4 TBI-MIL questionnaire. Persons were asked “During the past 4 years, have you had any injury (head or other) from any of the following (events)?.” Those individuals who did not endorse any injury event in the 4 years before the ANAM4 TBI-MIL assessment comprised the “no injury” group. Individuals were categorized in the “brain injury” group if they reported an injury event in the prior 4 years accompanied by an alteration of consciousness (defined by endorsing at least one of the following symptoms: feeling dazed and confused, experiencing a loss of consciousness, or experiencing loss of memory for the injury or post-traumatic amnesia for the event). Those brain injuries self-reported in the ANAM4 TBI-MIL questionnaire responses were presumed to be mild (rather than meeting moderate or severe classification criteria), as all individuals were actively serving in the military and scheduled for upcoming deployment duty. Detailed data regarding the exact date, type, and severity of injuries were not collected within the ANAM4 TBI-MIL. Those persons who reported an injury in the prior 4 years but did not report alteration or loss of consciousness or loss of memory for the injury event were categorized into the “nonbrain injury” groups. Persons in the two injury subgroups were further classified as reporting injury-related symptoms at the time of testing either at rest or upon exertion (current symptoms) or symptoms only at the time of injury (without current symptoms). By questionnaire design, only those persons endorsing an injury event were then subsequently queried about specific symptoms. To examine differences in the ACS and mood measures by injury subgroup, linear mixed model analyses were conducted. To evaluate individual injury subgroup differences, adjustment for multiple comparisons with the method of Games–Howell29 was applied. Additional mixed models were run to examine the ACS and mood measures by injury subgroups while adjusting for sex, age, and education. Percentile cut scores indicative of below and above average performance (at the 9th and 91st percentile, respectively30) were calculated for the ACS for the “no injury” group (<1.3 SD below the group mean). Within the four injured groups, the proportion of individuals with below average performance was determined. A set of post hoc sensitivity analyses was conducted to examine whether questionable performance levels (as determined by the PVI), more severe reported brain injury, or prior deployment influenced ACS differences observed across injury subgroups. Separate linear mixed effect models were conducted, after excluding those persons who (i) met criteria for questionable performance effort or (ii) reported loss of consciousness >20 minutes. We also examined the differences among the injury subgroups stratified by previous deployment history. All statistical analyses were conducted using SAS (version 9.3). Because of the large population size, statistical analyses were conducted with significance level α < 0.001. Cohen's d effect sizes also were computed. For data reduction purposes and to lessen the possibility of Type I error, statistical analyses only examined the ACS rather than each ANAM4 TBI-MIL performance test separately. RESULTS The U.S. military population completing ANAM4 TBI-MIL assessments as part of the DoD-wide mandated predeployment program from its onset through the end of December 2010, was on average 28.5 years of age (SD = 7.9) (Table II) at the time of assessment. A total of 64,568 persons (10.1%) were of Hispanic ethnicity. Army personnel made up the largest service branch represented (67%). Almost half (46.2%) of the personnel had deployed previously before the initiation of the DoD-wide Neurocognitive Functional Assessment Program, with the majority of the previous deployments (98%) being to Iraq or Afghanistan since 2001 as part of Operation Iraqi Freedom or Operation Enduring Freedom. TABLE II. Characteristics of Those Completing ANAM4 TBI-MIL Battery (n = 641,285) Variablea     N  %  Age  <21  92,417  14.41  21–30 Years  355,511  55.44  31–40 Years  136,648  21.31  >40 Years  56,709  8.84  Sex  Male  573,564  89.44  Female  67,721  10.56  Education  <High School  9,968  1.55  High School Graduate  531,543  82.89  College Graduate (4-Year Degree)  69,867  10.89  Advanced Degree  24,176  3.77  Unknown  5,731  0.89  Race  White  486,507  75.86  Black  93,503  14.58  Asian  19,567  3.05  American Indian  6,348  1.0  Other/Unknown  35,360  5.14  Rank  E1–E4  335,661  52.34  E5–E6  174,301  27.18  E7–E9  46,779  7.30  Officer (Includes Warrant)  84,544  13.18  Length of Time in Service, at Time of Assessment  <1 Year  38,364  5.98  1–<5 Years  276,362  43.10  5–<10 Years  137,628  21.46  10+ Years  179,508  27.99  Unknown (No Service Entry Date)  9,423  1.47  Branch of Service  Army  431,464  67.28  Air Force  91,802  14.32  Marine Corps  89,333  13.93  Navy  28,044  4.37  Other  642  0.10  Component  National Guard  119,071  18.57  Regular (Active Duty)  464,686  72.46  Reserve  57,528  8.97  AFQT/ASVAB Categoryb  I  26,101  4.07  II  186,247  29.04  III  312,191  48.68  IV or V  15,399  2.39  Unknown or not Available  101,347  15.80  Variablea     N  %  Age  <21  92,417  14.41  21–30 Years  355,511  55.44  31–40 Years  136,648  21.31  >40 Years  56,709  8.84  Sex  Male  573,564  89.44  Female  67,721  10.56  Education  <High School  9,968  1.55  High School Graduate  531,543  82.89  College Graduate (4-Year Degree)  69,867  10.89  Advanced Degree  24,176  3.77  Unknown  5,731  0.89  Race  White  486,507  75.86  Black  93,503  14.58  Asian  19,567  3.05  American Indian  6,348  1.0  Other/Unknown  35,360  5.14  Rank  E1–E4  335,661  52.34  E5–E6  174,301  27.18  E7–E9  46,779  7.30  Officer (Includes Warrant)  84,544  13.18  Length of Time in Service, at Time of Assessment  <1 Year  38,364  5.98  1–<5 Years  276,362  43.10  5–<10 Years  137,628  21.46  10+ Years  179,508  27.99  Unknown (No Service Entry Date)  9,423  1.47  Branch of Service  Army  431,464  67.28  Air Force  91,802  14.32  Marine Corps  89,333  13.93  Navy  28,044  4.37  Other  642  0.10  Component  National Guard  119,071  18.57  Regular (Active Duty)  464,686  72.46  Reserve  57,528  8.97  AFQT/ASVAB Categoryb  I  26,101  4.07  II  186,247  29.04  III  312,191  48.68  IV or V  15,399  2.39  Unknown or not Available  101,347  15.80  AFQT, Armed Forces Qualification Test; ASVAB, Armed Services Vocational Battery. a Data provided by DMDC. b AFQT/ASVAB data is primarily only available for enlisted personnel. Being in a lower category (i.e., Category I) indicates better proficiency. View Large TABLE II. Characteristics of Those Completing ANAM4 TBI-MIL Battery (n = 641,285) Variablea     N  %  Age  <21  92,417  14.41  21–30 Years  355,511  55.44  31–40 Years  136,648  21.31  >40 Years  56,709  8.84  Sex  Male  573,564  89.44  Female  67,721  10.56  Education  <High School  9,968  1.55  High School Graduate  531,543  82.89  College Graduate (4-Year Degree)  69,867  10.89  Advanced Degree  24,176  3.77  Unknown  5,731  0.89  Race  White  486,507  75.86  Black  93,503  14.58  Asian  19,567  3.05  American Indian  6,348  1.0  Other/Unknown  35,360  5.14  Rank  E1–E4  335,661  52.34  E5–E6  174,301  27.18  E7–E9  46,779  7.30  Officer (Includes Warrant)  84,544  13.18  Length of Time in Service, at Time of Assessment  <1 Year  38,364  5.98  1–<5 Years  276,362  43.10  5–<10 Years  137,628  21.46  10+ Years  179,508  27.99  Unknown (No Service Entry Date)  9,423  1.47  Branch of Service  Army  431,464  67.28  Air Force  91,802  14.32  Marine Corps  89,333  13.93  Navy  28,044  4.37  Other  642  0.10  Component  National Guard  119,071  18.57  Regular (Active Duty)  464,686  72.46  Reserve  57,528  8.97  AFQT/ASVAB Categoryb  I  26,101  4.07  II  186,247  29.04  III  312,191  48.68  IV or V  15,399  2.39  Unknown or not Available  101,347  15.80  Variablea     N  %  Age  <21  92,417  14.41  21–30 Years  355,511  55.44  31–40 Years  136,648  21.31  >40 Years  56,709  8.84  Sex  Male  573,564  89.44  Female  67,721  10.56  Education  <High School  9,968  1.55  High School Graduate  531,543  82.89  College Graduate (4-Year Degree)  69,867  10.89  Advanced Degree  24,176  3.77  Unknown  5,731  0.89  Race  White  486,507  75.86  Black  93,503  14.58  Asian  19,567  3.05  American Indian  6,348  1.0  Other/Unknown  35,360  5.14  Rank  E1–E4  335,661  52.34  E5–E6  174,301  27.18  E7–E9  46,779  7.30  Officer (Includes Warrant)  84,544  13.18  Length of Time in Service, at Time of Assessment  <1 Year  38,364  5.98  1–<5 Years  276,362  43.10  5–<10 Years  137,628  21.46  10+ Years  179,508  27.99  Unknown (No Service Entry Date)  9,423  1.47  Branch of Service  Army  431,464  67.28  Air Force  91,802  14.32  Marine Corps  89,333  13.93  Navy  28,044  4.37  Other  642  0.10  Component  National Guard  119,071  18.57  Regular (Active Duty)  464,686  72.46  Reserve  57,528  8.97  AFQT/ASVAB Categoryb  I  26,101  4.07  II  186,247  29.04  III  312,191  48.68  IV or V  15,399  2.39  Unknown or not Available  101,347  15.80  AFQT, Armed Forces Qualification Test; ASVAB, Armed Services Vocational Battery. a Data provided by DMDC. b AFQT/ASVAB data is primarily only available for enlisted personnel. Being in a lower category (i.e., Category I) indicates better proficiency. View Large The total number of U.S. military deployed by Fiscal years 2008, 2009, and 2010 was 628, 329, 647, 969, and 623,028, respectively (data report from DMDC, written communication, January 2013). Compared to the deployed U.S. military population serving in 2009, those completing the ANAM4 TBI-MIL during 2007 to 2010 were similar in terms of sex, race/ethnicity, and service component characteristics. They were somewhat more likely to be from the lower enlisted ranks and in Army service than the U.S. deployed population in 2009 (which was approximately 60% Army, 16% Air Force, 10% Marine Corps, and 15% Navy, with 42% from enlisted E1 to E4 ranks). The mean, standard deviation, and median values for each test are presented in Table III. Less than 2% (1.72%) of the 634,155 persons for whom the PVI was able to be computed met criteria for questionable performance effort (“no injury” group, 1.45%; “brain injury with current symptoms” group, 5.92%; “brain injury without current symptoms” group, 2.07%; “nonbrain injury with current symptoms” group, 3.84%; and “nonbrain injury without current symptoms” group, 1.86%). The mean PVI score overall was 1.29 (SD = 2.51; standard error of mean = 0.003). TABLE III. ANAM4 TBI-MIL Battery Performances by Test for Those Completing ANAM4 TBI-MIL Battery Test  Na  Variable  Mean (SD)  Median  Simple Reaction Time (SRT)  641,285  Mean RT  264.0 (117.9)  251.8  % Correct   100.0 (0.6)  100.0  TP  234.4 (31.6)  238.3  Code Substitution Learning (CDS)  641,031  Mean RT  1154.4 (280.2)  1100.7  % Correct    97.6 (3.0)  98.6  TP  53.2 (11.6)  53.2  Procedural Reaction Time (PRO)  640,350  Mean RT  592.0 (107.1)  573.5  % Correct  96.8 (4.6)  96.9  TP  100.5 (14.8)  101.7  Mathematical Processing (MTH)  639,518  Mean RT  2821.0 (818.0)  2674.9  % Correct  93.5 (7.5)  95.0  TP  21.5 (6.4)  21.1  Matching to Sample (M2S)  638,175  Mean RT  1693.6 (482.7)  1624.2  % Correct    94.5 (6.6)  95.0  TP  35.6 (10.9)  34.5  Code Substitution Delayed (CDD)  632,586  Mean RT  1245.3 (370.5)  1168.8  % Correct  91.3 (9.5)  94.4  TP   46.5 (15.8)  46.1  Simple Reaction Time (SR2)  640,912  Mean RT  263.7 (82.2)  251.4  % Correct  100 (0.4)  100.0  TP  234.5 (32.7)  238.6  Test  Na  Variable  Mean (SD)  Median  Simple Reaction Time (SRT)  641,285  Mean RT  264.0 (117.9)  251.8  % Correct   100.0 (0.6)  100.0  TP  234.4 (31.6)  238.3  Code Substitution Learning (CDS)  641,031  Mean RT  1154.4 (280.2)  1100.7  % Correct    97.6 (3.0)  98.6  TP  53.2 (11.6)  53.2  Procedural Reaction Time (PRO)  640,350  Mean RT  592.0 (107.1)  573.5  % Correct  96.8 (4.6)  96.9  TP  100.5 (14.8)  101.7  Mathematical Processing (MTH)  639,518  Mean RT  2821.0 (818.0)  2674.9  % Correct  93.5 (7.5)  95.0  TP  21.5 (6.4)  21.1  Matching to Sample (M2S)  638,175  Mean RT  1693.6 (482.7)  1624.2  % Correct    94.5 (6.6)  95.0  TP  35.6 (10.9)  34.5  Code Substitution Delayed (CDD)  632,586  Mean RT  1245.3 (370.5)  1168.8  % Correct  91.3 (9.5)  94.4  TP   46.5 (15.8)  46.1  Simple Reaction Time (SR2)  640,912  Mean RT  263.7 (82.2)  251.4  % Correct  100 (0.4)  100.0  TP  234.5 (32.7)  238.6  a Includes those individuals who completed the test on the first (or second in the case of retest) administration with >56% accuracy. RT, Response time; TP, Throughput. View Large TABLE III. ANAM4 TBI-MIL Battery Performances by Test for Those Completing ANAM4 TBI-MIL Battery Test  Na  Variable  Mean (SD)  Median  Simple Reaction Time (SRT)  641,285  Mean RT  264.0 (117.9)  251.8  % Correct   100.0 (0.6)  100.0  TP  234.4 (31.6)  238.3  Code Substitution Learning (CDS)  641,031  Mean RT  1154.4 (280.2)  1100.7  % Correct    97.6 (3.0)  98.6  TP  53.2 (11.6)  53.2  Procedural Reaction Time (PRO)  640,350  Mean RT  592.0 (107.1)  573.5  % Correct  96.8 (4.6)  96.9  TP  100.5 (14.8)  101.7  Mathematical Processing (MTH)  639,518  Mean RT  2821.0 (818.0)  2674.9  % Correct  93.5 (7.5)  95.0  TP  21.5 (6.4)  21.1  Matching to Sample (M2S)  638,175  Mean RT  1693.6 (482.7)  1624.2  % Correct    94.5 (6.6)  95.0  TP  35.6 (10.9)  34.5  Code Substitution Delayed (CDD)  632,586  Mean RT  1245.3 (370.5)  1168.8  % Correct  91.3 (9.5)  94.4  TP   46.5 (15.8)  46.1  Simple Reaction Time (SR2)  640,912  Mean RT  263.7 (82.2)  251.4  % Correct  100 (0.4)  100.0  TP  234.5 (32.7)  238.6  Test  Na  Variable  Mean (SD)  Median  Simple Reaction Time (SRT)  641,285  Mean RT  264.0 (117.9)  251.8  % Correct   100.0 (0.6)  100.0  TP  234.4 (31.6)  238.3  Code Substitution Learning (CDS)  641,031  Mean RT  1154.4 (280.2)  1100.7  % Correct    97.6 (3.0)  98.6  TP  53.2 (11.6)  53.2  Procedural Reaction Time (PRO)  640,350  Mean RT  592.0 (107.1)  573.5  % Correct  96.8 (4.6)  96.9  TP  100.5 (14.8)  101.7  Mathematical Processing (MTH)  639,518  Mean RT  2821.0 (818.0)  2674.9  % Correct  93.5 (7.5)  95.0  TP  21.5 (6.4)  21.1  Matching to Sample (M2S)  638,175  Mean RT  1693.6 (482.7)  1624.2  % Correct    94.5 (6.6)  95.0  TP  35.6 (10.9)  34.5  Code Substitution Delayed (CDD)  632,586  Mean RT  1245.3 (370.5)  1168.8  % Correct  91.3 (9.5)  94.4  TP   46.5 (15.8)  46.1  Simple Reaction Time (SR2)  640,912  Mean RT  263.7 (82.2)  251.4  % Correct  100 (0.4)  100.0  TP  234.5 (32.7)  238.6  a Includes those individuals who completed the test on the first (or second in the case of retest) administration with >56% accuracy. RT, Response time; TP, Throughput. View Large The correlations between TP, age, gender, and education were statistically significant for all tests (p < 0.0001) (Table IV). For age, all Pearson correlation coefficients were negative with the exception of MTH, which was positive (r = 0.139), indicating that older persons performed better on MTH. For sex, the point biserial correlations were all negative and <−0.10, except for MTH (r = 0.005). The point biserial correlations between education level and TP all tended to fall around zero and demonstrated a mixed pattern, where having a college or advanced degree was positively correlated with PRO, MTH, M2S, and SR2 but negatively correlated with SRT, CDS, and CDD. TABLE IV. Correlations Between ANAM4 TBI-MIL Test Throughput and Demographic Characteristics Test  Agea  Genderb  Education Levelb  SRT  −0.169  −0.085  −0.021  CDS  −0.291  −0.028  −0.051  PRO  −0.148  −0.019  0.021  MTH  0.139  0.005  0.229  M2S  −0.178  −0.099  0.004  CDD  −0.284  −0.034  −0.032  SR2  −0.126  −0.087  0.004  Test  Agea  Genderb  Education Levelb  SRT  −0.169  −0.085  −0.021  CDS  −0.291  −0.028  −0.051  PRO  −0.148  −0.019  0.021  MTH  0.139  0.005  0.229  M2S  −0.178  −0.099  0.004  CDD  −0.284  −0.034  −0.032  SR2  −0.126  −0.087  0.004  a Pearson's correlation coefficients. b Point biserial correlation coefficients (Sex [M = 0/F = 1]; Education [HS or less = 0/>HS = 1]). All correlation coefficients significant at p < 0.0001. View Large TABLE IV. Correlations Between ANAM4 TBI-MIL Test Throughput and Demographic Characteristics Test  Agea  Genderb  Education Levelb  SRT  −0.169  −0.085  −0.021  CDS  −0.291  −0.028  −0.051  PRO  −0.148  −0.019  0.021  MTH  0.139  0.005  0.229  M2S  −0.178  −0.099  0.004  CDD  −0.284  −0.034  −0.032  SR2  −0.126  −0.087  0.004  Test  Agea  Genderb  Education Levelb  SRT  −0.169  −0.085  −0.021  CDS  −0.291  −0.028  −0.051  PRO  −0.148  −0.019  0.021  MTH  0.139  0.005  0.229  M2S  −0.178  −0.099  0.004  CDD  −0.284  −0.034  −0.032  SR2  −0.126  −0.087  0.004  a Pearson's correlation coefficients. b Point biserial correlation coefficients (Sex [M = 0/F = 1]; Education [HS or less = 0/>HS = 1]). All correlation coefficients significant at p < 0.0001. View Large Almost 11% of the population reported having a brain injury in the 4 years before the assessment (Table V) and 7% reported incurring exclusively a nonbrain injury in the previous 4 years. The most prevalent mechanism resulting in the injury reported by either the “brain injury with current symptoms” or “nonbrain injury with current symptoms” groups was blast (50.7% and 33.2% respectively). Among the groups reporting “brain injury without current symptoms”, the most prevalent injury mechanisms reported were vehicular (26.2%) or sports (26.1%), while injury during sports (30.8%) was most prevalent among the “nonbrain injury without current symptoms” group. TABLE V. Description of Injury Groups Completing the ANAM4 TBI-MIL Battery Predeployment    ALL  No Injury in Prior 4 Years  Brain Injury in Prior 4 Years  Nonbrain Injury in Prior 4 Years  With Current Symptoms  Without Current Symptoms  With Current Symptoms  Without Current Symptoms  N (% of total)  641,285  521,605 (81.3)  25,349 (4.0)  45,123 (7.0)  7,952 (1.2)  41,256 (6.4)  Male, N (%)  573,564 (89.4)  463,357 (88.8)  23,886 (94.2)  42,127 (93.3)  7,080 (89.0)  37,114 (89.9)  Age (Mean [SD])  28.5 (7.9)  28.7 (8.0)  27.8 (6.7)  27.1 (6.9)  28.9 (7.5)  28.1 (7.5)  >High School, N (%)  94,043 (14.7)  81,819 (12.8)  1,576 (0.2)  4,600 (0.7)  701 (0.1)  5,347 (0.8)  Previously Deployed, N (%)  296,472 (46.2)  229,236 (44.0)  17,487 (69.0)  23,809 (52.8)  5,138 (64.6)  20,802 (50.4)  Injury Scenarioa:   Blast, N (%)      12,849 (50.7)  8,353 (18.5)  2,639 (33.2)  4,157 (10.1)   Bullets, N (%)      137 (0.5)  111 (0.3)  24 (0.3)  98 (0.2)   Fragment, N (%)      845 (3.3)  464 (1.0)  108 (1.4)  237 (0.6)   Vehicular, N (%)      8,405 (33.2)  11,801 (26.2)  1,961 (24.7)  11,592 (28.1)   Sports, N (%)      5,250 (20.7)  11,766 (26.1)  2,054 (25.8)  12,720 (30.8)   Fall, N (%)      7,440 (29.4)  10,767 (23.9)  2,049 (25.8)  8,502 (20.6)   Fight, N (%)      4,894 (19.3)  9,338 (20.7)  903 (11.4)  6,109 (14.8)   Other Blow, N (%)      6,414 (25.5)  9,998 (22.3)  999 (12.6)  4,563 (11.1)  ANAM4 Sleep Scale (Mean [SD])  2.22 (1.11)  2.17 (1.07)  2.94 (1.35)  2.40 (1.19)  2.66 (1.33)  2.24 (1.13)  ANAM4 Composite Scoreb (Mean[SEM])  0.073 (0.001)  0.096 (0.001)c  −0.347 (0.008)  0.054 (0.005)  −0.167 (0.013)  0.095 (0.006)     ALL  No Injury in Prior 4 Years  Brain Injury in Prior 4 Years  Nonbrain Injury in Prior 4 Years  With Current Symptoms  Without Current Symptoms  With Current Symptoms  Without Current Symptoms  N (% of total)  641,285  521,605 (81.3)  25,349 (4.0)  45,123 (7.0)  7,952 (1.2)  41,256 (6.4)  Male, N (%)  573,564 (89.4)  463,357 (88.8)  23,886 (94.2)  42,127 (93.3)  7,080 (89.0)  37,114 (89.9)  Age (Mean [SD])  28.5 (7.9)  28.7 (8.0)  27.8 (6.7)  27.1 (6.9)  28.9 (7.5)  28.1 (7.5)  >High School, N (%)  94,043 (14.7)  81,819 (12.8)  1,576 (0.2)  4,600 (0.7)  701 (0.1)  5,347 (0.8)  Previously Deployed, N (%)  296,472 (46.2)  229,236 (44.0)  17,487 (69.0)  23,809 (52.8)  5,138 (64.6)  20,802 (50.4)  Injury Scenarioa:   Blast, N (%)      12,849 (50.7)  8,353 (18.5)  2,639 (33.2)  4,157 (10.1)   Bullets, N (%)      137 (0.5)  111 (0.3)  24 (0.3)  98 (0.2)   Fragment, N (%)      845 (3.3)  464 (1.0)  108 (1.4)  237 (0.6)   Vehicular, N (%)      8,405 (33.2)  11,801 (26.2)  1,961 (24.7)  11,592 (28.1)   Sports, N (%)      5,250 (20.7)  11,766 (26.1)  2,054 (25.8)  12,720 (30.8)   Fall, N (%)      7,440 (29.4)  10,767 (23.9)  2,049 (25.8)  8,502 (20.6)   Fight, N (%)      4,894 (19.3)  9,338 (20.7)  903 (11.4)  6,109 (14.8)   Other Blow, N (%)      6,414 (25.5)  9,998 (22.3)  999 (12.6)  4,563 (11.1)  ANAM4 Sleep Scale (Mean [SD])  2.22 (1.11)  2.17 (1.07)  2.94 (1.35)  2.40 (1.19)  2.66 (1.33)  2.24 (1.13)  ANAM4 Composite Scoreb (Mean[SEM])  0.073 (0.001)  0.096 (0.001)c  −0.347 (0.008)  0.054 (0.005)  −0.167 (0.013)  0.095 (0.006)  SD, Standard deviation; SEM, Standard error of mean. a Responders can select more than one category so values will not add to 100%. b Higher values indicate better performance. Sample size for ANAM4 Composite Score, n = 627,887 (“no injury,” n = 511,038; “head injury with current symptoms,” n = 24,588; “brain Injury without current symptoms,” n = 44,197; “nonbrain injury with current symptoms,” n = 7,735; “nonbrain injury without current symptoms,” n = 40,329). c Effect sizes for difference between “no injury” and the four groups were −0.44 (“brain injury with current symptoms”), −0.04 (“brain Injury without current symptoms”), −0.26 (“nonbrain injury with current symptoms”), and 0.001 (“nonbrain injury without current symptoms”). View Large TABLE V. Description of Injury Groups Completing the ANAM4 TBI-MIL Battery Predeployment    ALL  No Injury in Prior 4 Years  Brain Injury in Prior 4 Years  Nonbrain Injury in Prior 4 Years  With Current Symptoms  Without Current Symptoms  With Current Symptoms  Without Current Symptoms  N (% of total)  641,285  521,605 (81.3)  25,349 (4.0)  45,123 (7.0)  7,952 (1.2)  41,256 (6.4)  Male, N (%)  573,564 (89.4)  463,357 (88.8)  23,886 (94.2)  42,127 (93.3)  7,080 (89.0)  37,114 (89.9)  Age (Mean [SD])  28.5 (7.9)  28.7 (8.0)  27.8 (6.7)  27.1 (6.9)  28.9 (7.5)  28.1 (7.5)  >High School, N (%)  94,043 (14.7)  81,819 (12.8)  1,576 (0.2)  4,600 (0.7)  701 (0.1)  5,347 (0.8)  Previously Deployed, N (%)  296,472 (46.2)  229,236 (44.0)  17,487 (69.0)  23,809 (52.8)  5,138 (64.6)  20,802 (50.4)  Injury Scenarioa:   Blast, N (%)      12,849 (50.7)  8,353 (18.5)  2,639 (33.2)  4,157 (10.1)   Bullets, N (%)      137 (0.5)  111 (0.3)  24 (0.3)  98 (0.2)   Fragment, N (%)      845 (3.3)  464 (1.0)  108 (1.4)  237 (0.6)   Vehicular, N (%)      8,405 (33.2)  11,801 (26.2)  1,961 (24.7)  11,592 (28.1)   Sports, N (%)      5,250 (20.7)  11,766 (26.1)  2,054 (25.8)  12,720 (30.8)   Fall, N (%)      7,440 (29.4)  10,767 (23.9)  2,049 (25.8)  8,502 (20.6)   Fight, N (%)      4,894 (19.3)  9,338 (20.7)  903 (11.4)  6,109 (14.8)   Other Blow, N (%)      6,414 (25.5)  9,998 (22.3)  999 (12.6)  4,563 (11.1)  ANAM4 Sleep Scale (Mean [SD])  2.22 (1.11)  2.17 (1.07)  2.94 (1.35)  2.40 (1.19)  2.66 (1.33)  2.24 (1.13)  ANAM4 Composite Scoreb (Mean[SEM])  0.073 (0.001)  0.096 (0.001)c  −0.347 (0.008)  0.054 (0.005)  −0.167 (0.013)  0.095 (0.006)     ALL  No Injury in Prior 4 Years  Brain Injury in Prior 4 Years  Nonbrain Injury in Prior 4 Years  With Current Symptoms  Without Current Symptoms  With Current Symptoms  Without Current Symptoms  N (% of total)  641,285  521,605 (81.3)  25,349 (4.0)  45,123 (7.0)  7,952 (1.2)  41,256 (6.4)  Male, N (%)  573,564 (89.4)  463,357 (88.8)  23,886 (94.2)  42,127 (93.3)  7,080 (89.0)  37,114 (89.9)  Age (Mean [SD])  28.5 (7.9)  28.7 (8.0)  27.8 (6.7)  27.1 (6.9)  28.9 (7.5)  28.1 (7.5)  >High School, N (%)  94,043 (14.7)  81,819 (12.8)  1,576 (0.2)  4,600 (0.7)  701 (0.1)  5,347 (0.8)  Previously Deployed, N (%)  296,472 (46.2)  229,236 (44.0)  17,487 (69.0)  23,809 (52.8)  5,138 (64.6)  20,802 (50.4)  Injury Scenarioa:   Blast, N (%)      12,849 (50.7)  8,353 (18.5)  2,639 (33.2)  4,157 (10.1)   Bullets, N (%)      137 (0.5)  111 (0.3)  24 (0.3)  98 (0.2)   Fragment, N (%)      845 (3.3)  464 (1.0)  108 (1.4)  237 (0.6)   Vehicular, N (%)      8,405 (33.2)  11,801 (26.2)  1,961 (24.7)  11,592 (28.1)   Sports, N (%)      5,250 (20.7)  11,766 (26.1)  2,054 (25.8)  12,720 (30.8)   Fall, N (%)      7,440 (29.4)  10,767 (23.9)  2,049 (25.8)  8,502 (20.6)   Fight, N (%)      4,894 (19.3)  9,338 (20.7)  903 (11.4)  6,109 (14.8)   Other Blow, N (%)      6,414 (25.5)  9,998 (22.3)  999 (12.6)  4,563 (11.1)  ANAM4 Sleep Scale (Mean [SD])  2.22 (1.11)  2.17 (1.07)  2.94 (1.35)  2.40 (1.19)  2.66 (1.33)  2.24 (1.13)  ANAM4 Composite Scoreb (Mean[SEM])  0.073 (0.001)  0.096 (0.001)c  −0.347 (0.008)  0.054 (0.005)  −0.167 (0.013)  0.095 (0.006)  SD, Standard deviation; SEM, Standard error of mean. a Responders can select more than one category so values will not add to 100%. b Higher values indicate better performance. Sample size for ANAM4 Composite Score, n = 627,887 (“no injury,” n = 511,038; “head injury with current symptoms,” n = 24,588; “brain Injury without current symptoms,” n = 44,197; “nonbrain injury with current symptoms,” n = 7,735; “nonbrain injury without current symptoms,” n = 40,329). c Effect sizes for difference between “no injury” and the four groups were −0.44 (“brain injury with current symptoms”), −0.04 (“brain Injury without current symptoms”), −0.26 (“nonbrain injury with current symptoms”), and 0.001 (“nonbrain injury without current symptoms”). View Large Approximately 50% of the “brain injury with current symptoms” group reported some loss of consciousness at the time of their injury, with headaches (67.2%) and ringing in the ears (47.2%) being the most prevalent symptoms reported as being present at the time of their injury (Table VI). Similarly, for the “nonbrain injured with current symptoms” group, headaches (28.2%) and ringing in the ears (20.2%) were the most prevalent symptoms reported at the time of injury. With respect to current symptoms, the two most prevalent symptoms in both groups were sleep problems (51.4% in brain injured and 34.8% in nonbrain injured) and irritability or short temper (49.9% in brain injured and 31.2% in nonbrain injured). TABLE VI. Description of Symptoms Reported by Injury Groups Completing the ANAM4TBI-MIL Task Battery at Predeployment Symptoms  Reporting Brain Injury in the Prior 4 Years  Reporting Nonbrain Injury in the Prior 4 Years  With Current Symptoms  Without Current Symptoms  With Current Symptoms  Without Current Symptoms  N = 25,349  N = 45,123  N = 7,952  N = 41,256  Dazed, Confused, Saw Stars (%)  86.6  78.7      Knocked out— <1 Minute (%)  31.2  27.6      Knocked out— From 1–20 Minutes (%)  14.8  10.0      Knocked out— >20 Minutes (%)   3.1   2.1      Did not Remember Injury (%)  16.6  11.7      Headaches (%)   At Time of Injury  67.2  61.4  28.2  21.7   Currentlya  48.5  —  30.7  —  Nausea/Vomiting (%)   At Time of Injury  20.7  12.5   3.8   2.7   Currently   6.8  —   3.8  —  Sensitivity to Bright Light/Noise (%)   At Time of Injury  33.9  17.8   8.4   3.4   Currently  28.6  —  14.1  —  Balance Problems/Dizziness (%)   At Time of Injury  38.5  28.9   8.8   5.0   Currently  23.4  —  11.8  —  Ringing in the Ears (%)   At Time of Injury  47.2  26.7  20.2   7.2   Currently  41.2  —  26.5  —  Sleep Problems (%)   At Time of Injury  35.1  11.9  15.8   4.2   Currently  51.4  —  34.8  —  Irritability (Short Temper) (%)   At Time of Injury  30.2  10.7  11.6   3.3   Currently  49.9  —  31.2  —  Memory Problems/Lapses (%)   At Time of Injury  33.2  13.5   8.2   2.3   Currently  49.4  —  26.1  —  Other Symptoms (%)   At Time of Injury   8.7   4.5  19.6   7.1   Currently  10.5  —  29.1  —  Symptoms  Reporting Brain Injury in the Prior 4 Years  Reporting Nonbrain Injury in the Prior 4 Years  With Current Symptoms  Without Current Symptoms  With Current Symptoms  Without Current Symptoms  N = 25,349  N = 45,123  N = 7,952  N = 41,256  Dazed, Confused, Saw Stars (%)  86.6  78.7      Knocked out— <1 Minute (%)  31.2  27.6      Knocked out— From 1–20 Minutes (%)  14.8  10.0      Knocked out— >20 Minutes (%)   3.1   2.1      Did not Remember Injury (%)  16.6  11.7      Headaches (%)   At Time of Injury  67.2  61.4  28.2  21.7   Currentlya  48.5  —  30.7  —  Nausea/Vomiting (%)   At Time of Injury  20.7  12.5   3.8   2.7   Currently   6.8  —   3.8  —  Sensitivity to Bright Light/Noise (%)   At Time of Injury  33.9  17.8   8.4   3.4   Currently  28.6  —  14.1  —  Balance Problems/Dizziness (%)   At Time of Injury  38.5  28.9   8.8   5.0   Currently  23.4  —  11.8  —  Ringing in the Ears (%)   At Time of Injury  47.2  26.7  20.2   7.2   Currently  41.2  —  26.5  —  Sleep Problems (%)   At Time of Injury  35.1  11.9  15.8   4.2   Currently  51.4  —  34.8  —  Irritability (Short Temper) (%)   At Time of Injury  30.2  10.7  11.6   3.3   Currently  49.9  —  31.2  —  Memory Problems/Lapses (%)   At Time of Injury  33.2  13.5   8.2   2.3   Currently  49.4  —  26.1  —  Other Symptoms (%)   At Time of Injury   8.7   4.5  19.6   7.1   Currently  10.5  —  29.1  —  a Defined as reporting symptom currently either while resting or upon exertion. View Large TABLE VI. Description of Symptoms Reported by Injury Groups Completing the ANAM4TBI-MIL Task Battery at Predeployment Symptoms  Reporting Brain Injury in the Prior 4 Years  Reporting Nonbrain Injury in the Prior 4 Years  With Current Symptoms  Without Current Symptoms  With Current Symptoms  Without Current Symptoms  N = 25,349  N = 45,123  N = 7,952  N = 41,256  Dazed, Confused, Saw Stars (%)  86.6  78.7      Knocked out— <1 Minute (%)  31.2  27.6      Knocked out— From 1–20 Minutes (%)  14.8  10.0      Knocked out— >20 Minutes (%)   3.1   2.1      Did not Remember Injury (%)  16.6  11.7      Headaches (%)   At Time of Injury  67.2  61.4  28.2  21.7   Currentlya  48.5  —  30.7  —  Nausea/Vomiting (%)   At Time of Injury  20.7  12.5   3.8   2.7   Currently   6.8  —   3.8  —  Sensitivity to Bright Light/Noise (%)   At Time of Injury  33.9  17.8   8.4   3.4   Currently  28.6  —  14.1  —  Balance Problems/Dizziness (%)   At Time of Injury  38.5  28.9   8.8   5.0   Currently  23.4  —  11.8  —  Ringing in the Ears (%)   At Time of Injury  47.2  26.7  20.2   7.2   Currently  41.2  —  26.5  —  Sleep Problems (%)   At Time of Injury  35.1  11.9  15.8   4.2   Currently  51.4  —  34.8  —  Irritability (Short Temper) (%)   At Time of Injury  30.2  10.7  11.6   3.3   Currently  49.9  —  31.2  —  Memory Problems/Lapses (%)   At Time of Injury  33.2  13.5   8.2   2.3   Currently  49.4  —  26.1  —  Other Symptoms (%)   At Time of Injury   8.7   4.5  19.6   7.1   Currently  10.5  —  29.1  —  Symptoms  Reporting Brain Injury in the Prior 4 Years  Reporting Nonbrain Injury in the Prior 4 Years  With Current Symptoms  Without Current Symptoms  With Current Symptoms  Without Current Symptoms  N = 25,349  N = 45,123  N = 7,952  N = 41,256  Dazed, Confused, Saw Stars (%)  86.6  78.7      Knocked out— <1 Minute (%)  31.2  27.6      Knocked out— From 1–20 Minutes (%)  14.8  10.0      Knocked out— >20 Minutes (%)   3.1   2.1      Did not Remember Injury (%)  16.6  11.7      Headaches (%)   At Time of Injury  67.2  61.4  28.2  21.7   Currentlya  48.5  —  30.7  —  Nausea/Vomiting (%)   At Time of Injury  20.7  12.5   3.8   2.7   Currently   6.8  —   3.8  —  Sensitivity to Bright Light/Noise (%)   At Time of Injury  33.9  17.8   8.4   3.4   Currently  28.6  —  14.1  —  Balance Problems/Dizziness (%)   At Time of Injury  38.5  28.9   8.8   5.0   Currently  23.4  —  11.8  —  Ringing in the Ears (%)   At Time of Injury  47.2  26.7  20.2   7.2   Currently  41.2  —  26.5  —  Sleep Problems (%)   At Time of Injury  35.1  11.9  15.8   4.2   Currently  51.4  —  34.8  —  Irritability (Short Temper) (%)   At Time of Injury  30.2  10.7  11.6   3.3   Currently  49.9  —  31.2  —  Memory Problems/Lapses (%)   At Time of Injury  33.2  13.5   8.2   2.3   Currently  49.4  —  26.1  —  Other Symptoms (%)   At Time of Injury   8.7   4.5  19.6   7.1   Currently  10.5  —  29.1  —  a Defined as reporting symptom currently either while resting or upon exertion. View Large The ACS differed significantly by injury group (F [4, 627886] = 1180.58, p < 0.0001) (Table V). No significant difference in ACS between the “no injury” and the “nonbrain injury without current symptoms” groups was observed. The “brain injury with current symptoms” group demonstrated a significantly reduced ACS indicating reduced proficiency compared to the “nonbrain injury with current symptoms” group. In turn, both injury groups with current symptoms recorded significantly lower ACSs compared to the “brain injury without current symptoms” group. Figure 2 presents the cumulative frequency distributions of the ACS for the “no injury” and “brain injury with current symptoms” groups. The medians (50th percentiles) of the two groups differ by 0.3 (“no injury:” 0.12 [SD 1.0; variance 1.03]); “brain injury with current symptoms:” −0.18 (SD 1.36; variance 1.84). At the lower tail of the distribution for the ACS, the “brain injury with current symptoms” group (21%) was two times more likely and the nonbrain injury with current symptoms” group (16%) was one and a half times more likely than the “no injury” group (9%) to perform in the below average range for the ACS. FIGURE 2. View largeDownload slide Cumulative frequency distribution of the ANAM Composite Score in persons in the “no injury” and “brain injury with current symptoms” groups. FIGURE 2. View largeDownload slide Cumulative frequency distribution of the ANAM Composite Score in persons in the “no injury” and “brain injury with current symptoms” groups. The ANAM4 TBI-MIL Sleep score (Table V) significantly differed by injury group (F [4,641,159] = 3708.16, p < 0.0001), with all injury groups showing significant differences from each other. For each of the mood state subscales, significant differences (all p < 0.0001) were observed by injury group (n = 641,275). The pattern of results was similar for each subscale, in that all injury groups differed from each other (Fig. 3). Both the “brain injury with current symptoms” followed by the “nonbrain injury with current symptoms” groups consistently endorsed significantly higher symptoms of restlessness, fatigue, anger, depression, and anxiety than the other three groups, whereas the “no injury” group reported significantly more positive feelings of vigor and happiness compared to the injury groups. FIGURE 3. View largeDownload slide Mood states reported by injury groups completing the ANAM4 TBI-MIL task battery at predeployment. FIGURE 3. View largeDownload slide Mood states reported by injury groups completing the ANAM4 TBI-MIL task battery at predeployment. After accounting for age, sex, or education differences among the injury subgroups, there was no difference in the pattern of significant results observed for the ACS, Sleep scale, and Mood subscales. In posthoc analyses, the pattern of significant results for the ACS by injury subgroup did not differ following exclusion of those persons who met criteria for questionable effort based on the PVI or exclusion of the subset of the brain-injured groups that reported loss of consciousness greater than 20 minutes. Also, the pattern of results was similar when stratified by previous deployment history: among the deployed subgroups, moderate effect sizes were observed when comparing the differences between the “no injury” group and the “brain injury with current symptoms” (d = −0.41) group and the “nonbrain injury with current symptoms” (d = −0.51) group. DISCUSSION The population-based AMP-D represents the first available research resource to enable the examination of neurocognitive profiles of the U.S. military population. Our cross-sectional results demonstrate the association between neurocognitive performance and reported prior injury, particularly among those who continue to experience symptoms, with the group reporting “brain injury with current symptoms” followed by the group reporting “nonbrain injury with current symptoms” demonstrating reduced proficiency (as assessed by the ANAM4 TBI-MIL Composite score) compared to those groups reporting “brain or nonbrain injury with no current symptoms or no injury.” Compared to those reporting “no injury,” military personnel reporting “brain injury with current symptoms” were two times more likely to function at below average levels. It is important to comment that what is statistically significant may not always translate into meaningful differences in biological or clinical terms.31 However, the observed moderate effect size magnitude for the difference in neurocognitive proficiency on the ANAM4 TBI-MIL battery between the “no injury” group and the “brain injury with current symptoms” group (d = 0.44), does suggest a clinically meaningful result; an effect to a lesser degree was found with the “nonbrain injured with current symptoms” (d = 0.24) group. From a population-based public health perspective, even a small magnitude shift in the group distribution toward poorer neurocognitive proficiency (indicative of subtle population shifts) may be widely relevant. Although less severe than observed in landmark studies by Needleman and colleagues in the late 1970s and early 1980s documenting a threefold difference in IQ levels <80 among high-lead exposed children,32,33 our results represent a similar implication at the population level. Even a small shift in the performance mean of the population related to prior (brain) injury with current symptoms could be viewed as a benchmark of change, which over time may lead to increasing number of individuals seeking care and connote significant implications for public health policy. Previously reported results have been inconsistent as to whether history of concussion is associated with poorer cognitive proficiency on computer-assisted cognitive testing34,–37 but prior studies did not further compare head injured groups with and without current symptoms. In this study, we observe significantly reduced cognitive proficiencies among those persons with a reported history of previous injury (brain and nonbrain) and who are currently experiencing symptoms. The temporal nature and number of injury events in relation to the time of assessment, injury classification criteria followed, and group-level factors (such as degree of effort or motivation, and role of other health comorbidities) may contribute to the differences in the results observed in this study. Our study addressed injury within a temporal window of the previous 4 years (rather than at any time in the past) and utilized brain/head injury criteria defined by consensus-based symptom reports and validated against a clinical interview diagnostic approach.38 Less than 2% of the population met criteria for questionable effort, which is decidedly lower than 6.3–27.9% reported by other studies39,40 involving computer-based neurocognitive assessment of brain injury between high school and college athletes, albeit using different metrics. There are a number of strengths to this study. By the structure of the AMP-D, this study permits the descriptive analyses of predeployment cognitive assessment of the total population of the U.S. military. Therefore, findings represent those of all deployed military, independent of health care–seeking behavior or other sampling biases. The reliance on self-report of injury events in a retrospective manner, in particular those specifics related to the severity and temporal nature of the injury related to the time of assessment, presents a limit to the study. Review of associated medical records pertaining to specific injury events may provide additional details, but it is important to note that not all injuries may result in the individual seeking clinical care. The current analytic framework of the AMP-D does not include the ability to address the role(s) of multiple potential confounding factors, such as comorbid mental and physical health conditions. Future analytic steps will integrate clinical medical encounter diagnostic data (for a population subset) into the AMP-D and thus enable analysis of the role of comorbid disorders, such as post-traumatic stress disorder and major depression, on performance. In addition, concordance analyses between reported brain and nonbrain injuries in ANAM4 TBI-MIL assessment and those injury events documented within the clinical healthcare system are planned. The influence of injury, not just brain injury, on neurocognitive performance over one's military career and in the years following service, warrants continued attention. The AMP-D resource fills a critical capability gap permitting the evaluation of population-based brain health and performance trends and examination of both positive and protective factors and adverse risk elements that may influence performance. ACKNOWLEDGMENTS We thank the staff at the U.S. Army Office of the Surgeon General, Neurocognitive Assessment Branch, as well as the DoD Defense Manpower Data Center for their support in this project. Funding for this project has been provided by the U.S. Army Medical Research and Materiel Command to the U.S. Army Research Institute of Environmental Medicine and through award #W81XWH-08-1-0021 (PI: SP Proctor) to the Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc. REFERENCES 1. Vasterling JJ, Proctor SP Understanding the neuropsychological consequences of deployment stress: a public health framework. J Int Neuropsychol Soc  2011; 17( 1): 1– 6. Google Scholar CrossRef Search ADS PubMed  2. Okie S Traumatic brain injury in the war zone. N Engl J Med  2005; 352( 20): 2043– 47. Google Scholar CrossRef Search ADS PubMed  3. Committee on Gulf War and Health Brain Injuries in Veterans and Long-term Health Outcomes: Gulf War and Health: Volume 7: Long-term Consequences of Traumatic Brain Injury . Washington, DC, The National Academies Press, 2009. 4. Corrigan JD, Hammond FM Traumatic brain injury as a chronic health condition. Arch Phys Med Rehabil  2013; 94( 6): 1199– 201. Google Scholar CrossRef Search ADS PubMed  5. Guskiewicz KM, Bruce SL, Cantu RC, et al.   Recommendations on management of sports-related concussion: summary of the National Athletic Trainers’ Association position statement. Neurosurg  2004; 55( 4): 891– 5. Google Scholar CrossRef Search ADS   6. Guskiewicz KM, Bruce SL, Cantu RC, et al.   National Athletic Trainers’ Association position statement: management of sport-related concussion. J Athl Train  2004; 39( 3): 280– 97. Google Scholar PubMed  7. US Government Accountability Office, Report to Congressional Addresses DoD Health Care Mental Health and Traumatic Brain Injury Screening Efforts Implemented, but Consistent Pre-deployment Medical Record Review Policies Needed. GAO-08-615 . Washington, DC, US GAO, 2008. Available at http://www.gao.gov/products/gao-08-615; accessed February 28, 2014. 8. Department of Defense, Health Affairs Memorandum on Baseline Pre-deployment Neurocognitive Functional Assessment . Washington, DC, Health Affairs, 2008. Available at http://www.health.mil/∼/media/MHS/Policy%20Files/Import/baseline_pre-deployment_neurocognitive_functional_assessment_-_interim_guidance.ashx; accessed February 28, 2014. 9. Vincent AS, Bleiberg J, Yan S, et al.   Reference data from the Automated Neuropsychological Assessment Metrics for use in traumatic brain injury in an active duty military sample. Mil Med  2008; 173: 836– 52. Google Scholar CrossRef Search ADS PubMed  10. Roebuck-Spencer TM, Reeves DL, Bleiberg J, et al.   Influence of demographics on computerized cognitive testing in a military sample. Mil Psychol  2008; 20: 187– 203. Google Scholar CrossRef Search ADS   11. Kaminski TW, Groff RM, Glutting JJ Examining the stability of Automated Neuropsychological Assessment Metric (ANAM) baseline test scores. J Clin Exp Neuropsychol  2009; 31: 689– 97. Google Scholar CrossRef Search ADS PubMed  12. Vincent AS, Roebuck-Spencer T, Gilliland K, Schlegel R Automated Neuropsychological Assessment Metrics (v4) Traumatic Injury Battery: military normative data. Mil Med  2012; 177( 3): 256– 69. Google Scholar CrossRef Search ADS PubMed  13. Warden DL, Bleiberg J, Cameron KL, et al.   Persistent prolongation of simple reaction time in sports concussion. Neurology  2001; 57( 3): 524– 6. Google Scholar CrossRef Search ADS PubMed  14. Bleiberg J, Cernich A, Cameron K, et al.   Duration of cognitive impairment after sports concussion. Neurosurg  2004; 54( 5): 1073– 8. Google Scholar CrossRef Search ADS   15. Sim A, Terrberry-Spohr L, Wilson KR Prolonged recovery of memory functioning after mild traumatic brain injury in adolescent athletes. J Neurosurg  2008; 108( 3): 511– 6. Google Scholar CrossRef Search ADS PubMed  16. Norris JN, Carr W, Herzig T, Labrie W, Sams R ANAM4 TBI reaction time-based tests have prognostic utility for acute concussion. Mil Med  2013; 178( 7): 767– 74. Google Scholar CrossRef Search ADS PubMed  17. Bryan C, Hernandez AM Magnitudes of decline on Automated Neuropsychological Assessment Metrics subtest scores relative to predeployment baseline performance among service members evaluated for traumatic brain injury in Iraq. J Head Trauma Rehabil  2012; 27( 1): 45– 54. Google Scholar CrossRef Search ADS PubMed  18. Coldren RL, Russell ML, Parish RV, Dretsch M, Kelly MP The ANAM lacks utility as a diagnostic or screening tool for concussion more than 10 days following injury. Mil Med  2012; 177( 2): 179– 83. Google Scholar CrossRef Search ADS PubMed  19. Kelly MP, Coldren RL, Parish RV, Dretsch MN, Russell ML Assessment of acute concussion in the combat environment. Arch Clin Neuropsychol  2012; 27( 4): 375– 88. Google Scholar CrossRef Search ADS PubMed  20. Woodhouse J, Heyanka DJ, Scott J, et al.   Efficacy of the ANAM General Neuropsychological Screening battery (ANAM GNS) for detecting neurocognitive impairment in a mixed clinical sample. Clin Neuropsychol  2013; 27( 3): 376– 85. Google Scholar CrossRef Search ADS PubMed  21. Army Times Pathway to a Fit and Healthy Force Improving Performance, Resilience, and Readiness in the Army . Available at http://armymedicine.mil/Pages/performance-triad.aspx; accessed March 14, 2014. 22. Baker M European Year of the Brain 2014: a new impulse to strengthen the alliance for brain health. Croat Med  2013; 54( 5): 417– 8. Google Scholar CrossRef Search ADS   23. Markoff J Obama seeking to boost study of human brain. New York Times . February 17, 2013. Available at http://www.nytimes.com/2013/02/18/science/project-seeks-to-build-map-of-human-brain.html; accessed January 29, 2014. 24. Department of Defense Comprehensive Policy on Neurocognitive Assessments by Military Services. Number 6490.13 . Department of Defense, 2013. Available at http://www.dtic.mil/whs/directives/corres/pdf/649013p.pdf; accessed February 28, 2014. 25. Vincent AS, Roebuck-Spencer T, Lopez MS, et al.   Effects of military deployment on cognitive functioning. Mil Med  2012; 177( 3): 248– 55. Google Scholar CrossRef Search ADS PubMed  26. Thorne DR Throughput: a simple performance index with desirable characteristics. Behav Res Methods  2006; 38: 569– 73. Google Scholar CrossRef Search ADS PubMed  27. Roebuck-Spencer T, Vincent AS, Twillie DA, et al.   Cognitive change associated with self-reported mild traumatic brain injury sustained during the OEF/OIF conflicts. Clin Neuropsychol  2012; 26( 3): 474– 89. Google Scholar CrossRef Search ADS   28. Roebuck-Spencer T, Vincent AS, Gilliland K, Johnson DR, Cooper DB Initial clinical validation of an embedded effort measure within the Automated Neuropsychology Assessment Metrics (ANAM). Arch Clin Neuropsych  2013; 28( 7): 700– 10. Google Scholar CrossRef Search ADS   29. Games PA, Howell JF Pairwise multiple comparison procedures with unequal n's and/or variances: a Monte Carol study. J Educ Behav Stat  1976; 1( 2): 113– 25. Google Scholar CrossRef Search ADS   30. Hannay HJ, Lezak MD The neuropsychology examination: interpretation. In: Neuropsychology Assessment, pp 113–156 . Edited by Lezak MD, Howieson DB, Loring DW New York, Oxford University Press, 2004. 31. Todd KH Clinical versus statistical significance in the assessment of pain relief. Ann Emergency Med  1996; 27( 4): 439– 41. Google Scholar CrossRef Search ADS   32. Needleman HL, Leviton A, Bellinger D Lead-associated intellectual deficits. N Engl J Med  1982; 306( 6): 367. Google Scholar PubMed  33. Bellinger DC What is an adverse effect? A possible resolution of clinical and epidemiological perspectives on neurobehavioral toxicity. Environ Res  2004; 95( 2004): 394– 405. Google Scholar CrossRef Search ADS PubMed  34. Matser JT, Kessels AG, Lezak MD, Troost J A dose-response relation of headers and concussions with cognitive impairment in professional soccer players. J Clin Exp Neuropsychol  2001; 23: 770– 4. Google Scholar CrossRef Search ADS PubMed  35. Broglio SP, Ferrara MS, Piland SG, Anderson RB Concussion history is not a predictor of computerized neurocognitive performance. Br J Sports Med  2006; 40: 802– 5. Google Scholar CrossRef Search ADS PubMed  36. Ivins BJ, Kane R, Schwab KA Performance on the Automated Neuropsychological Assessment Metrics in a nonclinical sample of soldiers screened for mild TBI after returning from Iraq and Afghanistan: a descriptive analysis. J Head Trauma Rehabil  2009; 24( 1): 24– 31. Google Scholar CrossRef Search ADS PubMed  37. Hutchinson M, Comper P, Mainwaring L, Richards D Normative data in a sample of Canadian university athletes using ANAM tests. J Clin Sport Psychol  2012; 6: 336– 50. Google Scholar CrossRef Search ADS   38. Schwab KA, Ivins B, Cramer G, et al.   Screening for traumatic brain injury in troops returning from deployment in Afghanistan and Iraq: initial investigation of the usefulness of a short screening tool for traumatic brain injury. J Head Trauma Rehabil  2007; 22: 377– 89. Google Scholar CrossRef Search ADS PubMed  39. Schatz P, Moser RS, Solomon GS, Ott SD, Karpf R Prevalence of invalid computerized baseline neurocognitive test results in high school and collegiate athletes. J Athl Train  2012; 47( 3): 289– 96. Google Scholar CrossRef Search ADS PubMed  40. Szabo A, Alosco ML, Fedor A, Gunstad J Invalid performance and the impact in national collegiate athletic association division I football players. J Athl Train  2013; 48( 6): 851– 5. Google Scholar CrossRef Search ADS PubMed  Reprint & Copyright © Association of Military Surgeons of the U.S. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Military Medicine Oxford University Press

Neurocognitive Performance and Prior Injury Among U.S. Department of Defense Military Personnel

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Oxford University Press
Copyright
Reprint & Copyright © Association of Military Surgeons of the U.S.
ISSN
0026-4075
eISSN
1930-613X
DOI
10.7205/MILMED-D-14-00298
pmid
26032381
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Abstract

ABSTRACT This study examined the neurocognitive performance of U.S. military personnel completing the Automated Neuropsychological Assessment Metrics (version 4) TBI Military (ANAM4 TBI-MIL) battery as part of the Department of Defense Neurocognitive Functional Assessment Program. Descriptive analyses utilizing the ANAM4TBI Military Performance Database were performed. We examined ANAM Composite Score (ACS) differences between five injury subgroups (no injury, brain injury with current symptoms, brain injury without current symptoms, nonbrain injury with current symptoms, and nonbrain injury without current symptoms) using general linear mixed modeling. Almost 11% (70,472/641,285) reported brain injury in the 4 years before assessment. The ACS differed significantly by injury group (p < 0.0001). In comparison to the no injury group, those reporting brain injury with current symptoms (d = −0.44) and nonbrain injury with current symptoms (d = −0.24) demonstrated significantly reduced ACS scores (p < 0.0001) indicative of reduced neurocognitive proficiency. In this population-based study of U.S. military personnel, neurocognitive performance was significantly associated with reported injury within the past 4 years among those experiencing current symptoms. Occupational programs focusing on prospective brain health of injured population groups are warranted. INTRODUCTION The prospective cognitive and neurological health of military personnel1 is of considerable concern, in light of the heightened awareness of the health consequences of traumatic brain injury (TBI) events and other experiences occurring in operational and training environments.2,3 Additionally, the publicity surrounding the high rate of sports-related head injury in high school, collegiate, and professional athletes has served to illuminate and drive research efforts to better understand the long-term effects of brain injury on health and performance.4 Computer-based cognitive testing programs have been employed as a tool to screen for injury-related changes in cognitive status.5,6 In 2008, a Congressionally mandated program was established requiring all Department of Defense (DoD) service members deploying to Iraq or Afghanistan to complete a computer-based neurocognitive assessment.7 To comply with DoD's clinical testing policy,8 the Neurocognitive Functional Assessment Program was initiated, which established baseline neurocognitive status of all U.S. service members within 12 months before deployment using the Automated Neuropsychological Assessment Metrics (ANAM; version 4) TBI Military (ANAM4 TBI-MIL) battery. The ANAM4 TBI-MIL is a computer-based set of tests designed to measure cognitive performance across several functional domains, including executive functioning, attention, memory, response time, and information processing speed (Center for the Study of Human Operator Performance ANAM4. TBI-MIL: User Manual. Norman, Oklahoma: Center for the Study of Human Operator Performance; University of Oklahoma, 2007). Previous studies have documented the psychometric properties of ANAM tests9,–11 and normative data for military personnel12 have been provided. ANAM tests have been shown to be sensitive to the effects of mild brain injury,13,–16 especially in the acute phases17,–19 following injury. More recently, the ANAM test battery has been demonstrated to validly detect impairments in a mixed clinical patient sample.20 For this project, we integrated the ANAM4 TBI-MIL data into an analytical database (ANAM4TBI Military Performance Database, AMP-D) to examine neurocognitive performance metrics and factors that may influence performance. Given the emerging focus of brain health as a public health issue worldwide in both military and civilian populations (e.g., Army Performance Triad, The Brain Research through Advancing Innovative Neurotechnologies Initiative, European Year of the Brain21,–23), knowledge and understanding of the role that particular factors, especially modifiable ones, play in neurocognitive performance is a critical requirement from which appropriate prevention, training, intervention, and treatment programs can be launched. In this report, we used the AMP-D to examine neurocognitive performance and mood state profiles of DoD personnel completing the ANAM4 TBI-MIL. We compared performance and mood among military personnel who reported having brain or nonbrain injuries in the 4 years before their first ANAM4 TBI-MIL assessment and those reporting no injury. We predicted that having experienced an injury within the past 4 years, particularly where symptoms persist, is associated with reduced neurocognitive proficiency and adverse mood states. METHODS The study protocol was reviewed and approved by the Institutional Review Board at the U.S. Army Research Institute of Environmental Medicine and complied with all institutional guidelines for the protection of human subjects. Study Population The study population included all U.S. military personnel (n = 671,435) who were administered the ANAM4 TBI-MIL battery starting in 2007 through December 2010 as part of the mandated clinical testing policy.7,8,24 Procedures The ANAM4 TBI-MIL is a battery of tests administered via laptop computer, which takes approximately 20 minutes to complete (Table I). ANAM4 TBI-MIL incorporates two questionnaires requesting demographic and injury information (Demographics, TBI Questionnaire), two questionnaires requiring self-assessment of current state of arousal and mood (Sleepiness Scale [SLP], Mood Scale [MOO]), and seven performance tests (Simple Reaction Time [SRT], Code Substitution-Learning [CDS], Procedural Reaction Time [PRO], Mathematical Processing [MTH], Matching to Sample [M2S], Code Substitution-Delayed [CDD], and Simple Reaction Time Repeated [SR2]). More detailed descriptions of these tests have been provided elsewhere.9,12,25 TABLE I. ANAM4 TBI-MIL Battery and Functional Domains Assessed Task List  Task Abbreviation  Task Description/Functional Domains  Task Parameters Examined  TBI Questionnaire  TBQ  Report of TBI/Other Injury in Past 4 years and Past and Current Symptomatology  Injury Event Type and Related Health Symptoms  Sleepiness Scale  SLP  Assessment of Current Level of Sleepiness  Response Options are Ratings 1–7  Mood Scale  MOO  Assessment of Current Mood State in 7 Categories (7 Subscales: Vigor, Happiness, Depression, Anger, Fatigue, Anxiety, and Restlessness)  Mean of the Adjective Scores for Each Subscale  Simple Reaction Time  SRT  Basic Neural Processing (Motor Activity Speed/Efficiency)  Mean RT, % Correct, Throughput  Code Substitution Learning  CDS  Associative Learning (Speed/Efficiency)  Mean RT, % Correct, Throughput  Procedural Reaction Time  PRO  Processing Speed (Choice Reaction Time Rule Adherence)  Mean RT, % Correct, Throughput  Mathematical Processing  MTH  Working Memory  Mean RT, % Correct, Throughput  Matching to Sample  M2S  Visual Spatial Memory  Mean RT, % Correct, Throughput  Code Substitution-Delayed  CDD  Memory (Delayed)  Mean RT, % Correct, Throughput  Simple Reaction Time (R)  SR2  Basic Neural Processing (Motor Activity Speed /Efficiency)  Mean RT, % Correct, Throughput  Task List  Task Abbreviation  Task Description/Functional Domains  Task Parameters Examined  TBI Questionnaire  TBQ  Report of TBI/Other Injury in Past 4 years and Past and Current Symptomatology  Injury Event Type and Related Health Symptoms  Sleepiness Scale  SLP  Assessment of Current Level of Sleepiness  Response Options are Ratings 1–7  Mood Scale  MOO  Assessment of Current Mood State in 7 Categories (7 Subscales: Vigor, Happiness, Depression, Anger, Fatigue, Anxiety, and Restlessness)  Mean of the Adjective Scores for Each Subscale  Simple Reaction Time  SRT  Basic Neural Processing (Motor Activity Speed/Efficiency)  Mean RT, % Correct, Throughput  Code Substitution Learning  CDS  Associative Learning (Speed/Efficiency)  Mean RT, % Correct, Throughput  Procedural Reaction Time  PRO  Processing Speed (Choice Reaction Time Rule Adherence)  Mean RT, % Correct, Throughput  Mathematical Processing  MTH  Working Memory  Mean RT, % Correct, Throughput  Matching to Sample  M2S  Visual Spatial Memory  Mean RT, % Correct, Throughput  Code Substitution-Delayed  CDD  Memory (Delayed)  Mean RT, % Correct, Throughput  Simple Reaction Time (R)  SR2  Basic Neural Processing (Motor Activity Speed /Efficiency)  Mean RT, % Correct, Throughput  (R), Task was repeated at the end of the battery administration to provide a measure of response variation, an indicator of fatigue over the administration time period. RT, Response Time. View Large TABLE I. ANAM4 TBI-MIL Battery and Functional Domains Assessed Task List  Task Abbreviation  Task Description/Functional Domains  Task Parameters Examined  TBI Questionnaire  TBQ  Report of TBI/Other Injury in Past 4 years and Past and Current Symptomatology  Injury Event Type and Related Health Symptoms  Sleepiness Scale  SLP  Assessment of Current Level of Sleepiness  Response Options are Ratings 1–7  Mood Scale  MOO  Assessment of Current Mood State in 7 Categories (7 Subscales: Vigor, Happiness, Depression, Anger, Fatigue, Anxiety, and Restlessness)  Mean of the Adjective Scores for Each Subscale  Simple Reaction Time  SRT  Basic Neural Processing (Motor Activity Speed/Efficiency)  Mean RT, % Correct, Throughput  Code Substitution Learning  CDS  Associative Learning (Speed/Efficiency)  Mean RT, % Correct, Throughput  Procedural Reaction Time  PRO  Processing Speed (Choice Reaction Time Rule Adherence)  Mean RT, % Correct, Throughput  Mathematical Processing  MTH  Working Memory  Mean RT, % Correct, Throughput  Matching to Sample  M2S  Visual Spatial Memory  Mean RT, % Correct, Throughput  Code Substitution-Delayed  CDD  Memory (Delayed)  Mean RT, % Correct, Throughput  Simple Reaction Time (R)  SR2  Basic Neural Processing (Motor Activity Speed /Efficiency)  Mean RT, % Correct, Throughput  Task List  Task Abbreviation  Task Description/Functional Domains  Task Parameters Examined  TBI Questionnaire  TBQ  Report of TBI/Other Injury in Past 4 years and Past and Current Symptomatology  Injury Event Type and Related Health Symptoms  Sleepiness Scale  SLP  Assessment of Current Level of Sleepiness  Response Options are Ratings 1–7  Mood Scale  MOO  Assessment of Current Mood State in 7 Categories (7 Subscales: Vigor, Happiness, Depression, Anger, Fatigue, Anxiety, and Restlessness)  Mean of the Adjective Scores for Each Subscale  Simple Reaction Time  SRT  Basic Neural Processing (Motor Activity Speed/Efficiency)  Mean RT, % Correct, Throughput  Code Substitution Learning  CDS  Associative Learning (Speed/Efficiency)  Mean RT, % Correct, Throughput  Procedural Reaction Time  PRO  Processing Speed (Choice Reaction Time Rule Adherence)  Mean RT, % Correct, Throughput  Mathematical Processing  MTH  Working Memory  Mean RT, % Correct, Throughput  Matching to Sample  M2S  Visual Spatial Memory  Mean RT, % Correct, Throughput  Code Substitution-Delayed  CDD  Memory (Delayed)  Mean RT, % Correct, Throughput  Simple Reaction Time (R)  SR2  Basic Neural Processing (Motor Activity Speed /Efficiency)  Mean RT, % Correct, Throughput  (R), Task was repeated at the end of the battery administration to provide a measure of response variation, an indicator of fatigue over the administration time period. RT, Response Time. View Large Under the DoD-mandated clinical testing program, ANAM4 TBI-MIL administration was conducted in a standardized manner by trained test proctors at designated sites. The battery was administered primarily in groups, during the daytime hours, in a quiet room. All except two test modules (CDD, SR2) began with practice items to assist in learning the procedures and instructions before the actual test data collection occurred. If a participant did not understand the instructions, test proctors were present to provide clarification and answer questions. Per field operational procedures, data for each test were screened upon completion for potentially invalid test performance (defined as accuracy scores less than or equal to 56%), which could indicate potential misunderstanding of directions or poor effort. Individuals with test performances falling below these accuracy criteria were provided with clarification of the test instructions and asked to repeat that given test. Individual data files of ANAM4 TBI-MIL assessments were obtained from the ANAM Program Office (Neurocognitive Assessment Branch), U.S. Army Office of the Surgeon General. Military service and deployment history data, as well as other demographic (e.g., age, education level, sex, race) and military service (rank, service branch, component, and occupation) information were requested and provided by the Defense Manpower Data Center (DMDC) for use in this project through approved research processes. These data sources were integrated to form the master database (AMP-D) housed and managed at U.S. Army Research Institute of Environmental Medicine. Data Analyses In this report, we examined the data from 641,285 individuals administered the ANAM4 TBI-MIL as part of the standard predeployment procedures. This subset includes those individuals 18 to 65 years of age who completed the TBI questionnaire module and at least the SRT test (the first test in the battery) with higher than 56% recorded task accuracy on the first administration (or second in the case of retest) administration and for whom pertinent DMDC personnel data were available. (Exclusions included: 79 due to missing linkage identifiers; 27,686 because they completed the battery for some other reason [such as for a clinical evaluation or postinjury assessment]; 18 who did not complete the TBI questionnaire module; 579 who did not meet SRT task accuracy criteria; and 1,798 because they were missing pertinent DMDC demographic information.) For those individuals who completed ANAM4 TBI-MIL more than once during this period due to multiple deployments between 2007 and 2010 (n = 73,702), only data from the first assessment date were included (Fig. 1). FIGURE 1. View largeDownload slide Flowchart diagram. FIGURE 1. View largeDownload slide Flowchart diagram. In addition to the SRT test, all other ANAM4 TBI-MIL performance tests (CDS, M2S, PRO, MTH, CDD, and SR2) were evaluated to determine whether each was completed with greater than 56% accuracy on the first or second test administration within the same calendar day, therefore satisfying test-specific field retest criteria. If a person did not meet the test-specific retest criteria or if test data were missing, their data for that test were not included in the analyses. The percentage of persons excluded by task was as follows: CDS, 0.04%; PRO, 0.15%; MTH, 0.28%; M2S, 0.49%; CDD, 1.35%; and SR2, 0.06%. The mean, median, and range values for all test-specific scores were computed. Mean response time (mean RT) for correct responses, percentage correct (% correct), and throughput (TP) (correct responses per minute of available response time) were the test parameters selected for analyses of the performance tasks. TP represents a combination of reaction time and accuracy.26 The Sleepiness Scale responses represent a current rating of sleepiness with possible scores ranging from 1 to 7 (higher number indicates greater sleepiness). For each of the seven Mood subscales, six adjectives are presented along with a response set ranging from “not at all” to “very much” (on a 0 to 6 point scale). The mean of the adjective responses for each of the seven Mood subscales was selected for analysis. Higher values indicate greater endorsement of the mood state dimension. To provide a measure of overall performance on the ANAM4 TBI-MIL cognitive tests, the ANAM composite score (ACS) was computed by converting TP scores for all tasks in the battery to T-scores relative to an age- and gender-matched normative group.12,25,27 The ACS is reported in standard deviation units with more negative values indicating poorer overall performance. In addition, the ANAM4 Performance Validity Index (PVI) was computed for each individual. The PVI provides an assessment of valid responding and is computed utilizing the accuracy and RT discrepancy scores from four ANAM4 TBI-MIL tasks: M2S, SRT, PRO, and CDS.28 The PVI total score ranges from 0 to 48 with higher scores indicating greater likelihood of atypical performance effort. In this report, the recommended cut point score of 10, representing a minimum of 90% specificity in an outpatient sample,28 was selected as an indicator of questionable performance effort. Pearson and point biserial correlation coefficients were computed to examine the relationship between TP and age, sex, and education level. To evaluate whether reporting an injury was associated with reduced cognitive proficiency or adverse mood, individuals were categorized into five injury subgroups (no injury, brain injury with current symptoms, brain injury with no current symptoms, nonbrain injury with current symptoms, and nonbrain injury with no current symptoms) based on their responses on the ANAM4 TBI-MIL questionnaire. Persons were asked “During the past 4 years, have you had any injury (head or other) from any of the following (events)?.” Those individuals who did not endorse any injury event in the 4 years before the ANAM4 TBI-MIL assessment comprised the “no injury” group. Individuals were categorized in the “brain injury” group if they reported an injury event in the prior 4 years accompanied by an alteration of consciousness (defined by endorsing at least one of the following symptoms: feeling dazed and confused, experiencing a loss of consciousness, or experiencing loss of memory for the injury or post-traumatic amnesia for the event). Those brain injuries self-reported in the ANAM4 TBI-MIL questionnaire responses were presumed to be mild (rather than meeting moderate or severe classification criteria), as all individuals were actively serving in the military and scheduled for upcoming deployment duty. Detailed data regarding the exact date, type, and severity of injuries were not collected within the ANAM4 TBI-MIL. Those persons who reported an injury in the prior 4 years but did not report alteration or loss of consciousness or loss of memory for the injury event were categorized into the “nonbrain injury” groups. Persons in the two injury subgroups were further classified as reporting injury-related symptoms at the time of testing either at rest or upon exertion (current symptoms) or symptoms only at the time of injury (without current symptoms). By questionnaire design, only those persons endorsing an injury event were then subsequently queried about specific symptoms. To examine differences in the ACS and mood measures by injury subgroup, linear mixed model analyses were conducted. To evaluate individual injury subgroup differences, adjustment for multiple comparisons with the method of Games–Howell29 was applied. Additional mixed models were run to examine the ACS and mood measures by injury subgroups while adjusting for sex, age, and education. Percentile cut scores indicative of below and above average performance (at the 9th and 91st percentile, respectively30) were calculated for the ACS for the “no injury” group (<1.3 SD below the group mean). Within the four injured groups, the proportion of individuals with below average performance was determined. A set of post hoc sensitivity analyses was conducted to examine whether questionable performance levels (as determined by the PVI), more severe reported brain injury, or prior deployment influenced ACS differences observed across injury subgroups. Separate linear mixed effect models were conducted, after excluding those persons who (i) met criteria for questionable performance effort or (ii) reported loss of consciousness >20 minutes. We also examined the differences among the injury subgroups stratified by previous deployment history. All statistical analyses were conducted using SAS (version 9.3). Because of the large population size, statistical analyses were conducted with significance level α < 0.001. Cohen's d effect sizes also were computed. For data reduction purposes and to lessen the possibility of Type I error, statistical analyses only examined the ACS rather than each ANAM4 TBI-MIL performance test separately. RESULTS The U.S. military population completing ANAM4 TBI-MIL assessments as part of the DoD-wide mandated predeployment program from its onset through the end of December 2010, was on average 28.5 years of age (SD = 7.9) (Table II) at the time of assessment. A total of 64,568 persons (10.1%) were of Hispanic ethnicity. Army personnel made up the largest service branch represented (67%). Almost half (46.2%) of the personnel had deployed previously before the initiation of the DoD-wide Neurocognitive Functional Assessment Program, with the majority of the previous deployments (98%) being to Iraq or Afghanistan since 2001 as part of Operation Iraqi Freedom or Operation Enduring Freedom. TABLE II. Characteristics of Those Completing ANAM4 TBI-MIL Battery (n = 641,285) Variablea     N  %  Age  <21  92,417  14.41  21–30 Years  355,511  55.44  31–40 Years  136,648  21.31  >40 Years  56,709  8.84  Sex  Male  573,564  89.44  Female  67,721  10.56  Education  <High School  9,968  1.55  High School Graduate  531,543  82.89  College Graduate (4-Year Degree)  69,867  10.89  Advanced Degree  24,176  3.77  Unknown  5,731  0.89  Race  White  486,507  75.86  Black  93,503  14.58  Asian  19,567  3.05  American Indian  6,348  1.0  Other/Unknown  35,360  5.14  Rank  E1–E4  335,661  52.34  E5–E6  174,301  27.18  E7–E9  46,779  7.30  Officer (Includes Warrant)  84,544  13.18  Length of Time in Service, at Time of Assessment  <1 Year  38,364  5.98  1–<5 Years  276,362  43.10  5–<10 Years  137,628  21.46  10+ Years  179,508  27.99  Unknown (No Service Entry Date)  9,423  1.47  Branch of Service  Army  431,464  67.28  Air Force  91,802  14.32  Marine Corps  89,333  13.93  Navy  28,044  4.37  Other  642  0.10  Component  National Guard  119,071  18.57  Regular (Active Duty)  464,686  72.46  Reserve  57,528  8.97  AFQT/ASVAB Categoryb  I  26,101  4.07  II  186,247  29.04  III  312,191  48.68  IV or V  15,399  2.39  Unknown or not Available  101,347  15.80  Variablea     N  %  Age  <21  92,417  14.41  21–30 Years  355,511  55.44  31–40 Years  136,648  21.31  >40 Years  56,709  8.84  Sex  Male  573,564  89.44  Female  67,721  10.56  Education  <High School  9,968  1.55  High School Graduate  531,543  82.89  College Graduate (4-Year Degree)  69,867  10.89  Advanced Degree  24,176  3.77  Unknown  5,731  0.89  Race  White  486,507  75.86  Black  93,503  14.58  Asian  19,567  3.05  American Indian  6,348  1.0  Other/Unknown  35,360  5.14  Rank  E1–E4  335,661  52.34  E5–E6  174,301  27.18  E7–E9  46,779  7.30  Officer (Includes Warrant)  84,544  13.18  Length of Time in Service, at Time of Assessment  <1 Year  38,364  5.98  1–<5 Years  276,362  43.10  5–<10 Years  137,628  21.46  10+ Years  179,508  27.99  Unknown (No Service Entry Date)  9,423  1.47  Branch of Service  Army  431,464  67.28  Air Force  91,802  14.32  Marine Corps  89,333  13.93  Navy  28,044  4.37  Other  642  0.10  Component  National Guard  119,071  18.57  Regular (Active Duty)  464,686  72.46  Reserve  57,528  8.97  AFQT/ASVAB Categoryb  I  26,101  4.07  II  186,247  29.04  III  312,191  48.68  IV or V  15,399  2.39  Unknown or not Available  101,347  15.80  AFQT, Armed Forces Qualification Test; ASVAB, Armed Services Vocational Battery. a Data provided by DMDC. b AFQT/ASVAB data is primarily only available for enlisted personnel. Being in a lower category (i.e., Category I) indicates better proficiency. View Large TABLE II. Characteristics of Those Completing ANAM4 TBI-MIL Battery (n = 641,285) Variablea     N  %  Age  <21  92,417  14.41  21–30 Years  355,511  55.44  31–40 Years  136,648  21.31  >40 Years  56,709  8.84  Sex  Male  573,564  89.44  Female  67,721  10.56  Education  <High School  9,968  1.55  High School Graduate  531,543  82.89  College Graduate (4-Year Degree)  69,867  10.89  Advanced Degree  24,176  3.77  Unknown  5,731  0.89  Race  White  486,507  75.86  Black  93,503  14.58  Asian  19,567  3.05  American Indian  6,348  1.0  Other/Unknown  35,360  5.14  Rank  E1–E4  335,661  52.34  E5–E6  174,301  27.18  E7–E9  46,779  7.30  Officer (Includes Warrant)  84,544  13.18  Length of Time in Service, at Time of Assessment  <1 Year  38,364  5.98  1–<5 Years  276,362  43.10  5–<10 Years  137,628  21.46  10+ Years  179,508  27.99  Unknown (No Service Entry Date)  9,423  1.47  Branch of Service  Army  431,464  67.28  Air Force  91,802  14.32  Marine Corps  89,333  13.93  Navy  28,044  4.37  Other  642  0.10  Component  National Guard  119,071  18.57  Regular (Active Duty)  464,686  72.46  Reserve  57,528  8.97  AFQT/ASVAB Categoryb  I  26,101  4.07  II  186,247  29.04  III  312,191  48.68  IV or V  15,399  2.39  Unknown or not Available  101,347  15.80  Variablea     N  %  Age  <21  92,417  14.41  21–30 Years  355,511  55.44  31–40 Years  136,648  21.31  >40 Years  56,709  8.84  Sex  Male  573,564  89.44  Female  67,721  10.56  Education  <High School  9,968  1.55  High School Graduate  531,543  82.89  College Graduate (4-Year Degree)  69,867  10.89  Advanced Degree  24,176  3.77  Unknown  5,731  0.89  Race  White  486,507  75.86  Black  93,503  14.58  Asian  19,567  3.05  American Indian  6,348  1.0  Other/Unknown  35,360  5.14  Rank  E1–E4  335,661  52.34  E5–E6  174,301  27.18  E7–E9  46,779  7.30  Officer (Includes Warrant)  84,544  13.18  Length of Time in Service, at Time of Assessment  <1 Year  38,364  5.98  1–<5 Years  276,362  43.10  5–<10 Years  137,628  21.46  10+ Years  179,508  27.99  Unknown (No Service Entry Date)  9,423  1.47  Branch of Service  Army  431,464  67.28  Air Force  91,802  14.32  Marine Corps  89,333  13.93  Navy  28,044  4.37  Other  642  0.10  Component  National Guard  119,071  18.57  Regular (Active Duty)  464,686  72.46  Reserve  57,528  8.97  AFQT/ASVAB Categoryb  I  26,101  4.07  II  186,247  29.04  III  312,191  48.68  IV or V  15,399  2.39  Unknown or not Available  101,347  15.80  AFQT, Armed Forces Qualification Test; ASVAB, Armed Services Vocational Battery. a Data provided by DMDC. b AFQT/ASVAB data is primarily only available for enlisted personnel. Being in a lower category (i.e., Category I) indicates better proficiency. View Large The total number of U.S. military deployed by Fiscal years 2008, 2009, and 2010 was 628, 329, 647, 969, and 623,028, respectively (data report from DMDC, written communication, January 2013). Compared to the deployed U.S. military population serving in 2009, those completing the ANAM4 TBI-MIL during 2007 to 2010 were similar in terms of sex, race/ethnicity, and service component characteristics. They were somewhat more likely to be from the lower enlisted ranks and in Army service than the U.S. deployed population in 2009 (which was approximately 60% Army, 16% Air Force, 10% Marine Corps, and 15% Navy, with 42% from enlisted E1 to E4 ranks). The mean, standard deviation, and median values for each test are presented in Table III. Less than 2% (1.72%) of the 634,155 persons for whom the PVI was able to be computed met criteria for questionable performance effort (“no injury” group, 1.45%; “brain injury with current symptoms” group, 5.92%; “brain injury without current symptoms” group, 2.07%; “nonbrain injury with current symptoms” group, 3.84%; and “nonbrain injury without current symptoms” group, 1.86%). The mean PVI score overall was 1.29 (SD = 2.51; standard error of mean = 0.003). TABLE III. ANAM4 TBI-MIL Battery Performances by Test for Those Completing ANAM4 TBI-MIL Battery Test  Na  Variable  Mean (SD)  Median  Simple Reaction Time (SRT)  641,285  Mean RT  264.0 (117.9)  251.8  % Correct   100.0 (0.6)  100.0  TP  234.4 (31.6)  238.3  Code Substitution Learning (CDS)  641,031  Mean RT  1154.4 (280.2)  1100.7  % Correct    97.6 (3.0)  98.6  TP  53.2 (11.6)  53.2  Procedural Reaction Time (PRO)  640,350  Mean RT  592.0 (107.1)  573.5  % Correct  96.8 (4.6)  96.9  TP  100.5 (14.8)  101.7  Mathematical Processing (MTH)  639,518  Mean RT  2821.0 (818.0)  2674.9  % Correct  93.5 (7.5)  95.0  TP  21.5 (6.4)  21.1  Matching to Sample (M2S)  638,175  Mean RT  1693.6 (482.7)  1624.2  % Correct    94.5 (6.6)  95.0  TP  35.6 (10.9)  34.5  Code Substitution Delayed (CDD)  632,586  Mean RT  1245.3 (370.5)  1168.8  % Correct  91.3 (9.5)  94.4  TP   46.5 (15.8)  46.1  Simple Reaction Time (SR2)  640,912  Mean RT  263.7 (82.2)  251.4  % Correct  100 (0.4)  100.0  TP  234.5 (32.7)  238.6  Test  Na  Variable  Mean (SD)  Median  Simple Reaction Time (SRT)  641,285  Mean RT  264.0 (117.9)  251.8  % Correct   100.0 (0.6)  100.0  TP  234.4 (31.6)  238.3  Code Substitution Learning (CDS)  641,031  Mean RT  1154.4 (280.2)  1100.7  % Correct    97.6 (3.0)  98.6  TP  53.2 (11.6)  53.2  Procedural Reaction Time (PRO)  640,350  Mean RT  592.0 (107.1)  573.5  % Correct  96.8 (4.6)  96.9  TP  100.5 (14.8)  101.7  Mathematical Processing (MTH)  639,518  Mean RT  2821.0 (818.0)  2674.9  % Correct  93.5 (7.5)  95.0  TP  21.5 (6.4)  21.1  Matching to Sample (M2S)  638,175  Mean RT  1693.6 (482.7)  1624.2  % Correct    94.5 (6.6)  95.0  TP  35.6 (10.9)  34.5  Code Substitution Delayed (CDD)  632,586  Mean RT  1245.3 (370.5)  1168.8  % Correct  91.3 (9.5)  94.4  TP   46.5 (15.8)  46.1  Simple Reaction Time (SR2)  640,912  Mean RT  263.7 (82.2)  251.4  % Correct  100 (0.4)  100.0  TP  234.5 (32.7)  238.6  a Includes those individuals who completed the test on the first (or second in the case of retest) administration with >56% accuracy. RT, Response time; TP, Throughput. View Large TABLE III. ANAM4 TBI-MIL Battery Performances by Test for Those Completing ANAM4 TBI-MIL Battery Test  Na  Variable  Mean (SD)  Median  Simple Reaction Time (SRT)  641,285  Mean RT  264.0 (117.9)  251.8  % Correct   100.0 (0.6)  100.0  TP  234.4 (31.6)  238.3  Code Substitution Learning (CDS)  641,031  Mean RT  1154.4 (280.2)  1100.7  % Correct    97.6 (3.0)  98.6  TP  53.2 (11.6)  53.2  Procedural Reaction Time (PRO)  640,350  Mean RT  592.0 (107.1)  573.5  % Correct  96.8 (4.6)  96.9  TP  100.5 (14.8)  101.7  Mathematical Processing (MTH)  639,518  Mean RT  2821.0 (818.0)  2674.9  % Correct  93.5 (7.5)  95.0  TP  21.5 (6.4)  21.1  Matching to Sample (M2S)  638,175  Mean RT  1693.6 (482.7)  1624.2  % Correct    94.5 (6.6)  95.0  TP  35.6 (10.9)  34.5  Code Substitution Delayed (CDD)  632,586  Mean RT  1245.3 (370.5)  1168.8  % Correct  91.3 (9.5)  94.4  TP   46.5 (15.8)  46.1  Simple Reaction Time (SR2)  640,912  Mean RT  263.7 (82.2)  251.4  % Correct  100 (0.4)  100.0  TP  234.5 (32.7)  238.6  Test  Na  Variable  Mean (SD)  Median  Simple Reaction Time (SRT)  641,285  Mean RT  264.0 (117.9)  251.8  % Correct   100.0 (0.6)  100.0  TP  234.4 (31.6)  238.3  Code Substitution Learning (CDS)  641,031  Mean RT  1154.4 (280.2)  1100.7  % Correct    97.6 (3.0)  98.6  TP  53.2 (11.6)  53.2  Procedural Reaction Time (PRO)  640,350  Mean RT  592.0 (107.1)  573.5  % Correct  96.8 (4.6)  96.9  TP  100.5 (14.8)  101.7  Mathematical Processing (MTH)  639,518  Mean RT  2821.0 (818.0)  2674.9  % Correct  93.5 (7.5)  95.0  TP  21.5 (6.4)  21.1  Matching to Sample (M2S)  638,175  Mean RT  1693.6 (482.7)  1624.2  % Correct    94.5 (6.6)  95.0  TP  35.6 (10.9)  34.5  Code Substitution Delayed (CDD)  632,586  Mean RT  1245.3 (370.5)  1168.8  % Correct  91.3 (9.5)  94.4  TP   46.5 (15.8)  46.1  Simple Reaction Time (SR2)  640,912  Mean RT  263.7 (82.2)  251.4  % Correct  100 (0.4)  100.0  TP  234.5 (32.7)  238.6  a Includes those individuals who completed the test on the first (or second in the case of retest) administration with >56% accuracy. RT, Response time; TP, Throughput. View Large The correlations between TP, age, gender, and education were statistically significant for all tests (p < 0.0001) (Table IV). For age, all Pearson correlation coefficients were negative with the exception of MTH, which was positive (r = 0.139), indicating that older persons performed better on MTH. For sex, the point biserial correlations were all negative and <−0.10, except for MTH (r = 0.005). The point biserial correlations between education level and TP all tended to fall around zero and demonstrated a mixed pattern, where having a college or advanced degree was positively correlated with PRO, MTH, M2S, and SR2 but negatively correlated with SRT, CDS, and CDD. TABLE IV. Correlations Between ANAM4 TBI-MIL Test Throughput and Demographic Characteristics Test  Agea  Genderb  Education Levelb  SRT  −0.169  −0.085  −0.021  CDS  −0.291  −0.028  −0.051  PRO  −0.148  −0.019  0.021  MTH  0.139  0.005  0.229  M2S  −0.178  −0.099  0.004  CDD  −0.284  −0.034  −0.032  SR2  −0.126  −0.087  0.004  Test  Agea  Genderb  Education Levelb  SRT  −0.169  −0.085  −0.021  CDS  −0.291  −0.028  −0.051  PRO  −0.148  −0.019  0.021  MTH  0.139  0.005  0.229  M2S  −0.178  −0.099  0.004  CDD  −0.284  −0.034  −0.032  SR2  −0.126  −0.087  0.004  a Pearson's correlation coefficients. b Point biserial correlation coefficients (Sex [M = 0/F = 1]; Education [HS or less = 0/>HS = 1]). All correlation coefficients significant at p < 0.0001. View Large TABLE IV. Correlations Between ANAM4 TBI-MIL Test Throughput and Demographic Characteristics Test  Agea  Genderb  Education Levelb  SRT  −0.169  −0.085  −0.021  CDS  −0.291  −0.028  −0.051  PRO  −0.148  −0.019  0.021  MTH  0.139  0.005  0.229  M2S  −0.178  −0.099  0.004  CDD  −0.284  −0.034  −0.032  SR2  −0.126  −0.087  0.004  Test  Agea  Genderb  Education Levelb  SRT  −0.169  −0.085  −0.021  CDS  −0.291  −0.028  −0.051  PRO  −0.148  −0.019  0.021  MTH  0.139  0.005  0.229  M2S  −0.178  −0.099  0.004  CDD  −0.284  −0.034  −0.032  SR2  −0.126  −0.087  0.004  a Pearson's correlation coefficients. b Point biserial correlation coefficients (Sex [M = 0/F = 1]; Education [HS or less = 0/>HS = 1]). All correlation coefficients significant at p < 0.0001. View Large Almost 11% of the population reported having a brain injury in the 4 years before the assessment (Table V) and 7% reported incurring exclusively a nonbrain injury in the previous 4 years. The most prevalent mechanism resulting in the injury reported by either the “brain injury with current symptoms” or “nonbrain injury with current symptoms” groups was blast (50.7% and 33.2% respectively). Among the groups reporting “brain injury without current symptoms”, the most prevalent injury mechanisms reported were vehicular (26.2%) or sports (26.1%), while injury during sports (30.8%) was most prevalent among the “nonbrain injury without current symptoms” group. TABLE V. Description of Injury Groups Completing the ANAM4 TBI-MIL Battery Predeployment    ALL  No Injury in Prior 4 Years  Brain Injury in Prior 4 Years  Nonbrain Injury in Prior 4 Years  With Current Symptoms  Without Current Symptoms  With Current Symptoms  Without Current Symptoms  N (% of total)  641,285  521,605 (81.3)  25,349 (4.0)  45,123 (7.0)  7,952 (1.2)  41,256 (6.4)  Male, N (%)  573,564 (89.4)  463,357 (88.8)  23,886 (94.2)  42,127 (93.3)  7,080 (89.0)  37,114 (89.9)  Age (Mean [SD])  28.5 (7.9)  28.7 (8.0)  27.8 (6.7)  27.1 (6.9)  28.9 (7.5)  28.1 (7.5)  >High School, N (%)  94,043 (14.7)  81,819 (12.8)  1,576 (0.2)  4,600 (0.7)  701 (0.1)  5,347 (0.8)  Previously Deployed, N (%)  296,472 (46.2)  229,236 (44.0)  17,487 (69.0)  23,809 (52.8)  5,138 (64.6)  20,802 (50.4)  Injury Scenarioa:   Blast, N (%)      12,849 (50.7)  8,353 (18.5)  2,639 (33.2)  4,157 (10.1)   Bullets, N (%)      137 (0.5)  111 (0.3)  24 (0.3)  98 (0.2)   Fragment, N (%)      845 (3.3)  464 (1.0)  108 (1.4)  237 (0.6)   Vehicular, N (%)      8,405 (33.2)  11,801 (26.2)  1,961 (24.7)  11,592 (28.1)   Sports, N (%)      5,250 (20.7)  11,766 (26.1)  2,054 (25.8)  12,720 (30.8)   Fall, N (%)      7,440 (29.4)  10,767 (23.9)  2,049 (25.8)  8,502 (20.6)   Fight, N (%)      4,894 (19.3)  9,338 (20.7)  903 (11.4)  6,109 (14.8)   Other Blow, N (%)      6,414 (25.5)  9,998 (22.3)  999 (12.6)  4,563 (11.1)  ANAM4 Sleep Scale (Mean [SD])  2.22 (1.11)  2.17 (1.07)  2.94 (1.35)  2.40 (1.19)  2.66 (1.33)  2.24 (1.13)  ANAM4 Composite Scoreb (Mean[SEM])  0.073 (0.001)  0.096 (0.001)c  −0.347 (0.008)  0.054 (0.005)  −0.167 (0.013)  0.095 (0.006)     ALL  No Injury in Prior 4 Years  Brain Injury in Prior 4 Years  Nonbrain Injury in Prior 4 Years  With Current Symptoms  Without Current Symptoms  With Current Symptoms  Without Current Symptoms  N (% of total)  641,285  521,605 (81.3)  25,349 (4.0)  45,123 (7.0)  7,952 (1.2)  41,256 (6.4)  Male, N (%)  573,564 (89.4)  463,357 (88.8)  23,886 (94.2)  42,127 (93.3)  7,080 (89.0)  37,114 (89.9)  Age (Mean [SD])  28.5 (7.9)  28.7 (8.0)  27.8 (6.7)  27.1 (6.9)  28.9 (7.5)  28.1 (7.5)  >High School, N (%)  94,043 (14.7)  81,819 (12.8)  1,576 (0.2)  4,600 (0.7)  701 (0.1)  5,347 (0.8)  Previously Deployed, N (%)  296,472 (46.2)  229,236 (44.0)  17,487 (69.0)  23,809 (52.8)  5,138 (64.6)  20,802 (50.4)  Injury Scenarioa:   Blast, N (%)      12,849 (50.7)  8,353 (18.5)  2,639 (33.2)  4,157 (10.1)   Bullets, N (%)      137 (0.5)  111 (0.3)  24 (0.3)  98 (0.2)   Fragment, N (%)      845 (3.3)  464 (1.0)  108 (1.4)  237 (0.6)   Vehicular, N (%)      8,405 (33.2)  11,801 (26.2)  1,961 (24.7)  11,592 (28.1)   Sports, N (%)      5,250 (20.7)  11,766 (26.1)  2,054 (25.8)  12,720 (30.8)   Fall, N (%)      7,440 (29.4)  10,767 (23.9)  2,049 (25.8)  8,502 (20.6)   Fight, N (%)      4,894 (19.3)  9,338 (20.7)  903 (11.4)  6,109 (14.8)   Other Blow, N (%)      6,414 (25.5)  9,998 (22.3)  999 (12.6)  4,563 (11.1)  ANAM4 Sleep Scale (Mean [SD])  2.22 (1.11)  2.17 (1.07)  2.94 (1.35)  2.40 (1.19)  2.66 (1.33)  2.24 (1.13)  ANAM4 Composite Scoreb (Mean[SEM])  0.073 (0.001)  0.096 (0.001)c  −0.347 (0.008)  0.054 (0.005)  −0.167 (0.013)  0.095 (0.006)  SD, Standard deviation; SEM, Standard error of mean. a Responders can select more than one category so values will not add to 100%. b Higher values indicate better performance. Sample size for ANAM4 Composite Score, n = 627,887 (“no injury,” n = 511,038; “head injury with current symptoms,” n = 24,588; “brain Injury without current symptoms,” n = 44,197; “nonbrain injury with current symptoms,” n = 7,735; “nonbrain injury without current symptoms,” n = 40,329). c Effect sizes for difference between “no injury” and the four groups were −0.44 (“brain injury with current symptoms”), −0.04 (“brain Injury without current symptoms”), −0.26 (“nonbrain injury with current symptoms”), and 0.001 (“nonbrain injury without current symptoms”). View Large TABLE V. Description of Injury Groups Completing the ANAM4 TBI-MIL Battery Predeployment    ALL  No Injury in Prior 4 Years  Brain Injury in Prior 4 Years  Nonbrain Injury in Prior 4 Years  With Current Symptoms  Without Current Symptoms  With Current Symptoms  Without Current Symptoms  N (% of total)  641,285  521,605 (81.3)  25,349 (4.0)  45,123 (7.0)  7,952 (1.2)  41,256 (6.4)  Male, N (%)  573,564 (89.4)  463,357 (88.8)  23,886 (94.2)  42,127 (93.3)  7,080 (89.0)  37,114 (89.9)  Age (Mean [SD])  28.5 (7.9)  28.7 (8.0)  27.8 (6.7)  27.1 (6.9)  28.9 (7.5)  28.1 (7.5)  >High School, N (%)  94,043 (14.7)  81,819 (12.8)  1,576 (0.2)  4,600 (0.7)  701 (0.1)  5,347 (0.8)  Previously Deployed, N (%)  296,472 (46.2)  229,236 (44.0)  17,487 (69.0)  23,809 (52.8)  5,138 (64.6)  20,802 (50.4)  Injury Scenarioa:   Blast, N (%)      12,849 (50.7)  8,353 (18.5)  2,639 (33.2)  4,157 (10.1)   Bullets, N (%)      137 (0.5)  111 (0.3)  24 (0.3)  98 (0.2)   Fragment, N (%)      845 (3.3)  464 (1.0)  108 (1.4)  237 (0.6)   Vehicular, N (%)      8,405 (33.2)  11,801 (26.2)  1,961 (24.7)  11,592 (28.1)   Sports, N (%)      5,250 (20.7)  11,766 (26.1)  2,054 (25.8)  12,720 (30.8)   Fall, N (%)      7,440 (29.4)  10,767 (23.9)  2,049 (25.8)  8,502 (20.6)   Fight, N (%)      4,894 (19.3)  9,338 (20.7)  903 (11.4)  6,109 (14.8)   Other Blow, N (%)      6,414 (25.5)  9,998 (22.3)  999 (12.6)  4,563 (11.1)  ANAM4 Sleep Scale (Mean [SD])  2.22 (1.11)  2.17 (1.07)  2.94 (1.35)  2.40 (1.19)  2.66 (1.33)  2.24 (1.13)  ANAM4 Composite Scoreb (Mean[SEM])  0.073 (0.001)  0.096 (0.001)c  −0.347 (0.008)  0.054 (0.005)  −0.167 (0.013)  0.095 (0.006)     ALL  No Injury in Prior 4 Years  Brain Injury in Prior 4 Years  Nonbrain Injury in Prior 4 Years  With Current Symptoms  Without Current Symptoms  With Current Symptoms  Without Current Symptoms  N (% of total)  641,285  521,605 (81.3)  25,349 (4.0)  45,123 (7.0)  7,952 (1.2)  41,256 (6.4)  Male, N (%)  573,564 (89.4)  463,357 (88.8)  23,886 (94.2)  42,127 (93.3)  7,080 (89.0)  37,114 (89.9)  Age (Mean [SD])  28.5 (7.9)  28.7 (8.0)  27.8 (6.7)  27.1 (6.9)  28.9 (7.5)  28.1 (7.5)  >High School, N (%)  94,043 (14.7)  81,819 (12.8)  1,576 (0.2)  4,600 (0.7)  701 (0.1)  5,347 (0.8)  Previously Deployed, N (%)  296,472 (46.2)  229,236 (44.0)  17,487 (69.0)  23,809 (52.8)  5,138 (64.6)  20,802 (50.4)  Injury Scenarioa:   Blast, N (%)      12,849 (50.7)  8,353 (18.5)  2,639 (33.2)  4,157 (10.1)   Bullets, N (%)      137 (0.5)  111 (0.3)  24 (0.3)  98 (0.2)   Fragment, N (%)      845 (3.3)  464 (1.0)  108 (1.4)  237 (0.6)   Vehicular, N (%)      8,405 (33.2)  11,801 (26.2)  1,961 (24.7)  11,592 (28.1)   Sports, N (%)      5,250 (20.7)  11,766 (26.1)  2,054 (25.8)  12,720 (30.8)   Fall, N (%)      7,440 (29.4)  10,767 (23.9)  2,049 (25.8)  8,502 (20.6)   Fight, N (%)      4,894 (19.3)  9,338 (20.7)  903 (11.4)  6,109 (14.8)   Other Blow, N (%)      6,414 (25.5)  9,998 (22.3)  999 (12.6)  4,563 (11.1)  ANAM4 Sleep Scale (Mean [SD])  2.22 (1.11)  2.17 (1.07)  2.94 (1.35)  2.40 (1.19)  2.66 (1.33)  2.24 (1.13)  ANAM4 Composite Scoreb (Mean[SEM])  0.073 (0.001)  0.096 (0.001)c  −0.347 (0.008)  0.054 (0.005)  −0.167 (0.013)  0.095 (0.006)  SD, Standard deviation; SEM, Standard error of mean. a Responders can select more than one category so values will not add to 100%. b Higher values indicate better performance. Sample size for ANAM4 Composite Score, n = 627,887 (“no injury,” n = 511,038; “head injury with current symptoms,” n = 24,588; “brain Injury without current symptoms,” n = 44,197; “nonbrain injury with current symptoms,” n = 7,735; “nonbrain injury without current symptoms,” n = 40,329). c Effect sizes for difference between “no injury” and the four groups were −0.44 (“brain injury with current symptoms”), −0.04 (“brain Injury without current symptoms”), −0.26 (“nonbrain injury with current symptoms”), and 0.001 (“nonbrain injury without current symptoms”). View Large Approximately 50% of the “brain injury with current symptoms” group reported some loss of consciousness at the time of their injury, with headaches (67.2%) and ringing in the ears (47.2%) being the most prevalent symptoms reported as being present at the time of their injury (Table VI). Similarly, for the “nonbrain injured with current symptoms” group, headaches (28.2%) and ringing in the ears (20.2%) were the most prevalent symptoms reported at the time of injury. With respect to current symptoms, the two most prevalent symptoms in both groups were sleep problems (51.4% in brain injured and 34.8% in nonbrain injured) and irritability or short temper (49.9% in brain injured and 31.2% in nonbrain injured). TABLE VI. Description of Symptoms Reported by Injury Groups Completing the ANAM4TBI-MIL Task Battery at Predeployment Symptoms  Reporting Brain Injury in the Prior 4 Years  Reporting Nonbrain Injury in the Prior 4 Years  With Current Symptoms  Without Current Symptoms  With Current Symptoms  Without Current Symptoms  N = 25,349  N = 45,123  N = 7,952  N = 41,256  Dazed, Confused, Saw Stars (%)  86.6  78.7      Knocked out— <1 Minute (%)  31.2  27.6      Knocked out— From 1–20 Minutes (%)  14.8  10.0      Knocked out— >20 Minutes (%)   3.1   2.1      Did not Remember Injury (%)  16.6  11.7      Headaches (%)   At Time of Injury  67.2  61.4  28.2  21.7   Currentlya  48.5  —  30.7  —  Nausea/Vomiting (%)   At Time of Injury  20.7  12.5   3.8   2.7   Currently   6.8  —   3.8  —  Sensitivity to Bright Light/Noise (%)   At Time of Injury  33.9  17.8   8.4   3.4   Currently  28.6  —  14.1  —  Balance Problems/Dizziness (%)   At Time of Injury  38.5  28.9   8.8   5.0   Currently  23.4  —  11.8  —  Ringing in the Ears (%)   At Time of Injury  47.2  26.7  20.2   7.2   Currently  41.2  —  26.5  —  Sleep Problems (%)   At Time of Injury  35.1  11.9  15.8   4.2   Currently  51.4  —  34.8  —  Irritability (Short Temper) (%)   At Time of Injury  30.2  10.7  11.6   3.3   Currently  49.9  —  31.2  —  Memory Problems/Lapses (%)   At Time of Injury  33.2  13.5   8.2   2.3   Currently  49.4  —  26.1  —  Other Symptoms (%)   At Time of Injury   8.7   4.5  19.6   7.1   Currently  10.5  —  29.1  —  Symptoms  Reporting Brain Injury in the Prior 4 Years  Reporting Nonbrain Injury in the Prior 4 Years  With Current Symptoms  Without Current Symptoms  With Current Symptoms  Without Current Symptoms  N = 25,349  N = 45,123  N = 7,952  N = 41,256  Dazed, Confused, Saw Stars (%)  86.6  78.7      Knocked out— <1 Minute (%)  31.2  27.6      Knocked out— From 1–20 Minutes (%)  14.8  10.0      Knocked out— >20 Minutes (%)   3.1   2.1      Did not Remember Injury (%)  16.6  11.7      Headaches (%)   At Time of Injury  67.2  61.4  28.2  21.7   Currentlya  48.5  —  30.7  —  Nausea/Vomiting (%)   At Time of Injury  20.7  12.5   3.8   2.7   Currently   6.8  —   3.8  —  Sensitivity to Bright Light/Noise (%)   At Time of Injury  33.9  17.8   8.4   3.4   Currently  28.6  —  14.1  —  Balance Problems/Dizziness (%)   At Time of Injury  38.5  28.9   8.8   5.0   Currently  23.4  —  11.8  —  Ringing in the Ears (%)   At Time of Injury  47.2  26.7  20.2   7.2   Currently  41.2  —  26.5  —  Sleep Problems (%)   At Time of Injury  35.1  11.9  15.8   4.2   Currently  51.4  —  34.8  —  Irritability (Short Temper) (%)   At Time of Injury  30.2  10.7  11.6   3.3   Currently  49.9  —  31.2  —  Memory Problems/Lapses (%)   At Time of Injury  33.2  13.5   8.2   2.3   Currently  49.4  —  26.1  —  Other Symptoms (%)   At Time of Injury   8.7   4.5  19.6   7.1   Currently  10.5  —  29.1  —  a Defined as reporting symptom currently either while resting or upon exertion. View Large TABLE VI. Description of Symptoms Reported by Injury Groups Completing the ANAM4TBI-MIL Task Battery at Predeployment Symptoms  Reporting Brain Injury in the Prior 4 Years  Reporting Nonbrain Injury in the Prior 4 Years  With Current Symptoms  Without Current Symptoms  With Current Symptoms  Without Current Symptoms  N = 25,349  N = 45,123  N = 7,952  N = 41,256  Dazed, Confused, Saw Stars (%)  86.6  78.7      Knocked out— <1 Minute (%)  31.2  27.6      Knocked out— From 1–20 Minutes (%)  14.8  10.0      Knocked out— >20 Minutes (%)   3.1   2.1      Did not Remember Injury (%)  16.6  11.7      Headaches (%)   At Time of Injury  67.2  61.4  28.2  21.7   Currentlya  48.5  —  30.7  —  Nausea/Vomiting (%)   At Time of Injury  20.7  12.5   3.8   2.7   Currently   6.8  —   3.8  —  Sensitivity to Bright Light/Noise (%)   At Time of Injury  33.9  17.8   8.4   3.4   Currently  28.6  —  14.1  —  Balance Problems/Dizziness (%)   At Time of Injury  38.5  28.9   8.8   5.0   Currently  23.4  —  11.8  —  Ringing in the Ears (%)   At Time of Injury  47.2  26.7  20.2   7.2   Currently  41.2  —  26.5  —  Sleep Problems (%)   At Time of Injury  35.1  11.9  15.8   4.2   Currently  51.4  —  34.8  —  Irritability (Short Temper) (%)   At Time of Injury  30.2  10.7  11.6   3.3   Currently  49.9  —  31.2  —  Memory Problems/Lapses (%)   At Time of Injury  33.2  13.5   8.2   2.3   Currently  49.4  —  26.1  —  Other Symptoms (%)   At Time of Injury   8.7   4.5  19.6   7.1   Currently  10.5  —  29.1  —  Symptoms  Reporting Brain Injury in the Prior 4 Years  Reporting Nonbrain Injury in the Prior 4 Years  With Current Symptoms  Without Current Symptoms  With Current Symptoms  Without Current Symptoms  N = 25,349  N = 45,123  N = 7,952  N = 41,256  Dazed, Confused, Saw Stars (%)  86.6  78.7      Knocked out— <1 Minute (%)  31.2  27.6      Knocked out— From 1–20 Minutes (%)  14.8  10.0      Knocked out— >20 Minutes (%)   3.1   2.1      Did not Remember Injury (%)  16.6  11.7      Headaches (%)   At Time of Injury  67.2  61.4  28.2  21.7   Currentlya  48.5  —  30.7  —  Nausea/Vomiting (%)   At Time of Injury  20.7  12.5   3.8   2.7   Currently   6.8  —   3.8  —  Sensitivity to Bright Light/Noise (%)   At Time of Injury  33.9  17.8   8.4   3.4   Currently  28.6  —  14.1  —  Balance Problems/Dizziness (%)   At Time of Injury  38.5  28.9   8.8   5.0   Currently  23.4  —  11.8  —  Ringing in the Ears (%)   At Time of Injury  47.2  26.7  20.2   7.2   Currently  41.2  —  26.5  —  Sleep Problems (%)   At Time of Injury  35.1  11.9  15.8   4.2   Currently  51.4  —  34.8  —  Irritability (Short Temper) (%)   At Time of Injury  30.2  10.7  11.6   3.3   Currently  49.9  —  31.2  —  Memory Problems/Lapses (%)   At Time of Injury  33.2  13.5   8.2   2.3   Currently  49.4  —  26.1  —  Other Symptoms (%)   At Time of Injury   8.7   4.5  19.6   7.1   Currently  10.5  —  29.1  —  a Defined as reporting symptom currently either while resting or upon exertion. View Large The ACS differed significantly by injury group (F [4, 627886] = 1180.58, p < 0.0001) (Table V). No significant difference in ACS between the “no injury” and the “nonbrain injury without current symptoms” groups was observed. The “brain injury with current symptoms” group demonstrated a significantly reduced ACS indicating reduced proficiency compared to the “nonbrain injury with current symptoms” group. In turn, both injury groups with current symptoms recorded significantly lower ACSs compared to the “brain injury without current symptoms” group. Figure 2 presents the cumulative frequency distributions of the ACS for the “no injury” and “brain injury with current symptoms” groups. The medians (50th percentiles) of the two groups differ by 0.3 (“no injury:” 0.12 [SD 1.0; variance 1.03]); “brain injury with current symptoms:” −0.18 (SD 1.36; variance 1.84). At the lower tail of the distribution for the ACS, the “brain injury with current symptoms” group (21%) was two times more likely and the nonbrain injury with current symptoms” group (16%) was one and a half times more likely than the “no injury” group (9%) to perform in the below average range for the ACS. FIGURE 2. View largeDownload slide Cumulative frequency distribution of the ANAM Composite Score in persons in the “no injury” and “brain injury with current symptoms” groups. FIGURE 2. View largeDownload slide Cumulative frequency distribution of the ANAM Composite Score in persons in the “no injury” and “brain injury with current symptoms” groups. The ANAM4 TBI-MIL Sleep score (Table V) significantly differed by injury group (F [4,641,159] = 3708.16, p < 0.0001), with all injury groups showing significant differences from each other. For each of the mood state subscales, significant differences (all p < 0.0001) were observed by injury group (n = 641,275). The pattern of results was similar for each subscale, in that all injury groups differed from each other (Fig. 3). Both the “brain injury with current symptoms” followed by the “nonbrain injury with current symptoms” groups consistently endorsed significantly higher symptoms of restlessness, fatigue, anger, depression, and anxiety than the other three groups, whereas the “no injury” group reported significantly more positive feelings of vigor and happiness compared to the injury groups. FIGURE 3. View largeDownload slide Mood states reported by injury groups completing the ANAM4 TBI-MIL task battery at predeployment. FIGURE 3. View largeDownload slide Mood states reported by injury groups completing the ANAM4 TBI-MIL task battery at predeployment. After accounting for age, sex, or education differences among the injury subgroups, there was no difference in the pattern of significant results observed for the ACS, Sleep scale, and Mood subscales. In posthoc analyses, the pattern of significant results for the ACS by injury subgroup did not differ following exclusion of those persons who met criteria for questionable effort based on the PVI or exclusion of the subset of the brain-injured groups that reported loss of consciousness greater than 20 minutes. Also, the pattern of results was similar when stratified by previous deployment history: among the deployed subgroups, moderate effect sizes were observed when comparing the differences between the “no injury” group and the “brain injury with current symptoms” (d = −0.41) group and the “nonbrain injury with current symptoms” (d = −0.51) group. DISCUSSION The population-based AMP-D represents the first available research resource to enable the examination of neurocognitive profiles of the U.S. military population. Our cross-sectional results demonstrate the association between neurocognitive performance and reported prior injury, particularly among those who continue to experience symptoms, with the group reporting “brain injury with current symptoms” followed by the group reporting “nonbrain injury with current symptoms” demonstrating reduced proficiency (as assessed by the ANAM4 TBI-MIL Composite score) compared to those groups reporting “brain or nonbrain injury with no current symptoms or no injury.” Compared to those reporting “no injury,” military personnel reporting “brain injury with current symptoms” were two times more likely to function at below average levels. It is important to comment that what is statistically significant may not always translate into meaningful differences in biological or clinical terms.31 However, the observed moderate effect size magnitude for the difference in neurocognitive proficiency on the ANAM4 TBI-MIL battery between the “no injury” group and the “brain injury with current symptoms” group (d = 0.44), does suggest a clinically meaningful result; an effect to a lesser degree was found with the “nonbrain injured with current symptoms” (d = 0.24) group. From a population-based public health perspective, even a small magnitude shift in the group distribution toward poorer neurocognitive proficiency (indicative of subtle population shifts) may be widely relevant. Although less severe than observed in landmark studies by Needleman and colleagues in the late 1970s and early 1980s documenting a threefold difference in IQ levels <80 among high-lead exposed children,32,33 our results represent a similar implication at the population level. Even a small shift in the performance mean of the population related to prior (brain) injury with current symptoms could be viewed as a benchmark of change, which over time may lead to increasing number of individuals seeking care and connote significant implications for public health policy. Previously reported results have been inconsistent as to whether history of concussion is associated with poorer cognitive proficiency on computer-assisted cognitive testing34,–37 but prior studies did not further compare head injured groups with and without current symptoms. In this study, we observe significantly reduced cognitive proficiencies among those persons with a reported history of previous injury (brain and nonbrain) and who are currently experiencing symptoms. The temporal nature and number of injury events in relation to the time of assessment, injury classification criteria followed, and group-level factors (such as degree of effort or motivation, and role of other health comorbidities) may contribute to the differences in the results observed in this study. Our study addressed injury within a temporal window of the previous 4 years (rather than at any time in the past) and utilized brain/head injury criteria defined by consensus-based symptom reports and validated against a clinical interview diagnostic approach.38 Less than 2% of the population met criteria for questionable effort, which is decidedly lower than 6.3–27.9% reported by other studies39,40 involving computer-based neurocognitive assessment of brain injury between high school and college athletes, albeit using different metrics. There are a number of strengths to this study. By the structure of the AMP-D, this study permits the descriptive analyses of predeployment cognitive assessment of the total population of the U.S. military. Therefore, findings represent those of all deployed military, independent of health care–seeking behavior or other sampling biases. The reliance on self-report of injury events in a retrospective manner, in particular those specifics related to the severity and temporal nature of the injury related to the time of assessment, presents a limit to the study. Review of associated medical records pertaining to specific injury events may provide additional details, but it is important to note that not all injuries may result in the individual seeking clinical care. The current analytic framework of the AMP-D does not include the ability to address the role(s) of multiple potential confounding factors, such as comorbid mental and physical health conditions. Future analytic steps will integrate clinical medical encounter diagnostic data (for a population subset) into the AMP-D and thus enable analysis of the role of comorbid disorders, such as post-traumatic stress disorder and major depression, on performance. In addition, concordance analyses between reported brain and nonbrain injuries in ANAM4 TBI-MIL assessment and those injury events documented within the clinical healthcare system are planned. The influence of injury, not just brain injury, on neurocognitive performance over one's military career and in the years following service, warrants continued attention. The AMP-D resource fills a critical capability gap permitting the evaluation of population-based brain health and performance trends and examination of both positive and protective factors and adverse risk elements that may influence performance. ACKNOWLEDGMENTS We thank the staff at the U.S. Army Office of the Surgeon General, Neurocognitive Assessment Branch, as well as the DoD Defense Manpower Data Center for their support in this project. Funding for this project has been provided by the U.S. Army Medical Research and Materiel Command to the U.S. Army Research Institute of Environmental Medicine and through award #W81XWH-08-1-0021 (PI: SP Proctor) to the Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc. REFERENCES 1. Vasterling JJ, Proctor SP Understanding the neuropsychological consequences of deployment stress: a public health framework. J Int Neuropsychol Soc  2011; 17( 1): 1– 6. Google Scholar CrossRef Search ADS PubMed  2. Okie S Traumatic brain injury in the war zone. N Engl J Med  2005; 352( 20): 2043– 47. Google Scholar CrossRef Search ADS PubMed  3. Committee on Gulf War and Health Brain Injuries in Veterans and Long-term Health Outcomes: Gulf War and Health: Volume 7: Long-term Consequences of Traumatic Brain Injury . Washington, DC, The National Academies Press, 2009. 4. Corrigan JD, Hammond FM Traumatic brain injury as a chronic health condition. 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Military MedicineOxford University Press

Published: Jun 1, 2015

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