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Physical Performance Is Associated with Executive Functioning in Older African American Women

Physical Performance Is Associated with Executive Functioning in Older African American Women SAGE-Hindawi Access to Research Journal of Aging Research Volume 2011, Article ID 578609, 8 pages doi:10.4061/2011/578609 Research Article Physical Performance Is Associated with Executive Functioning in Older African American Women 1 2 Brooke C. Schneider and Peter A. Lichtenberg Psychology Service, VA Greater Los Angeles Healthcare Center, Los Angeles, CA 90073, USA Institute of Gerontology, Wayne State University, Detroit, Michigan 48202, USA Correspondence should be addressed to Brooke C. Schneider, schneider.brooke@gmail.com Received 1 September 2010; Revised 1 December 2010; Accepted 4 January 2011 Academic Editor: Iris Reuter Copyright © 2011 B. C. Schneider and P. A. Lichtenberg. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. An older adult’s ability to perform physical tasks is predictive of disability onset and is associated with declines in cognition. Risk factors for physical performance declines among African Americans, a group with the highest rates of disability, remain understudied. This study sought to identify demographic, health, and cognitive factors associated with lower-extremity physical performance in a sample of 106 African American women ages 56 to 91. After controlling for global cognitive functioning (Mini Mental State Exam), physical performance was associated with executive functioning (Stroop Color/Word), but not visuospatial construction (WASI Block Design) or processing speed (Trail Making Test, Part A). Executive functioning remained associated with physical performance after entry of demographic variables, exercise, depression, disease burden, and body mass index (BMI). Age, and BMI were also significant in this model. Executive functioning, age and BMI are associated with lower-extremity physical performance among older African American women. 1. Introduction than both white adults [4] and suburban African Americans [5]. Impairments in physical and cognitive functioning, as well While much evidence exists for the relationship between as onset of chronic diseases, are often feared in later life as cognitive functioning and ADL declines [6–8], fewer studies such changes lead to dependence in tasks of daily living, have focused on the associations between physical perfor- depression, and hospitalization. Compared to white elders, mance and cognition, specifically executive functioning, in African American older adults experience a greater number minority populations. Executive functioning encompasses of years exposed to the negative impacts of chronic disease a broad range of cognitive abilities such as the planning, and functional disability [1] making disability intervention sequencing, and execution of complex goal-directed behav- especially important for this minority group. The field of iors characteristic of IADLs (instrumental activities of daily gerontology has identified lower-extremity physical perfor- living) [9, 10]. Amongst cognitive domains such as mem- mance measures as key for identification of early changes ory, language, visuospatial ability, and psychomotor speed, that may lead to disability in older adults. Lower-extremity executive functioning is deemed as essential to preserved measures of physical performance are predictive of several functional status [11, 12]. Prior studies have found that outcomes in later life including declines in activities of daily executive functioning is related to mobility and balance living (ADLs), hospitalization, risk for death, nursing home among older adults [13–15]; however, this relationship placement, and hip fracture [2, 3]. Reflecting the observed may be attenuated after accounting for disease burden racial and socioeconomic discrepancies in rates of disability in African American elders [16]. Additionally, it remains among older adults, African American elders score more unclear whether performance of physical tasks may involve poorly on performance-based measures of physical function executive functioning more than other domains of cognition 2 Journal of Aging Research and whether screening measures of global cognitive func- Prior to participation, all participants provided signed tioning, such as the Mini Mental Status Exam (MMSE), consent. Subjects were recruited from independent living which are commonly used in disability risk assessments, centers, community centers and senior apartments through may adequately predict physical performance declines [14, presentations within the community given by the PI. Fliers 17, 18]. stating that the aim of the study is to understand “health Neuroimaging studies and clinical observation of age- and cognitive functioning in older African American adults” related cognitive disorders such as Parkinson’s disease and were also given to potential participants. Individuals were vascular dementia, provide evidence that changes in brain excluded if they (1) did not self-report as African American structures result in impairments in both cognitive function- or black; (2) were unable to speak English fluently; (3) had ing [9] and physical performance [19]. The frontal subcor- major hearing or vision loss; and/or (4) were below age tical region, implicated in tasks of executive functioning, is 55. Because the dataset contained a significantly greater particularly sensitive to effects of cardiovascular risk factors proportion of females (87.7%), male participants were (CVRFs) such as atherosclerosis, hypertension, stroke, and excluded from these analyses. diabetes [20–24]. Vascular burden is associated with presence A summary of participant characteristics is presented in of white matter hyperintensities (WMHs), brain atrophy Table 1 and mean raw scores on cognitive measures for the and infarcts. Older adults with compromise to the white final sample are presented in Table 2.The final sample was matter pathways connecting subcortical and frontal regions comprised of 106 African American women ages 56 to 91 secondary to vascular processes demonstrate poor executive (mean = 71.83; SD = 7.73), and with 6 to 18 years of formal functioning, slow gait speed and depression [15, 25]. The education (mean = 12.74; SD = 2.45). co-occurrence of these symptoms is associated with greater 2.2. Measures and Procedures. Measures reported in this functional dependency [19], poorer physical performance study were administered as part of a larger evaluation that [15], and mortality [26]. involved data collection on demographics, physical health, African American adults have higher body mass index cognition, health behaviors, and mental health in urban (BMI), and a greater number of health conditions, par- African American elders for a dissertation project. Data ticularly CVRFs such as hypertension and diabetes, when was collected in an individual interview session format by compared to their white, same-gender peers [27, 28]. Both three trained interviewers who were supervised by a research obesity and inactivity are associated with disability [29]. psychologist (PL). Participants were informed of the length Exercise interventions have been shown to improve scores on of the test battery prior to participation. However, due to measures of lower-extremity functioning [30]and decrease participant time restraints leading them to leave early or risk for mortality, frailty, disease [31]and obesity[29]; arrive late, as well as slowness in completing the measures, however, it remains unclear what level of exercise is needed the battery occasionally had to be shortened or terminated to decrease disability risk. In order to develop interventions before all measures were completed. This led to slight and delay disability onset within African American elders, a differences in sample size across measures. The average time high-risk group of older adults, further work is needed to to complete the battery was two hours. understand the impact of medical conditions and the poten- tial benefit of exercise to prevent early disability. The goals of this study are to (1) identify whether a spe- 2.3. Cognitive Measures. Fuld object memory evaluation cific domain of cognition versus global cognitive functioning (FOME) [32]. TheFOME is a measureof verbal memory may be uniquely associated with physical performance; and that involves recall of 10 common objects. Recall trials are (2) to examine relationships between physical performance separated by a distraction task to minimize the effects of and a range of factors associated with disability risk including short-term memory. cognition, depression, exercise, disease burden, BMI and Mini Mental Status Exam (MMSE) [33]. The MMSE is demographics in a sample of community-dwelling African an 11-item screening tool used to obtain an estimate of an American older women. Based on previous research it was individual’s global cognitive functioning and orientation to predicted that executive functioning would be significantly date,time, andplace.Scores range from 0 to30 with higher associated with physical performance while other domains scores indicating better cognitive functioning. of cognition would not and that physical performance would Stroop Color/Word subtest (Stroop C/W) [34]. The be related to demographics, depression, exercise, health, and Stroop C/W test is a measure of processing speed and mental cognition. flexibility. The Stroop test is comprised of three subtasks: color word naming, color naming, and naming the color of ink a color name is printed in. For example, saying “green” 2. Methods when the word “red” is printed in green ink. Third subtask 2.1. Sample. Participants were drawn from the Health, is an interference trial that requires inhibition and mental Disability and Cognitive Function in Urban African Amer- flexibility. Time to completion was recorded for each trial. ican Older Adults dataset, which includes 130 community- Trail Making Test, Part A (TMT-A) [35]. Part A of the dwelling African American adults between the ages of 55 TMT is a measure of attention and psychomotor processing and 100 who resided in the city of Detroit. This project speed in which participants are asked to connect numbers received approval from the Institutional Review Board, in numerical order (1-2-3 and so on) as quickly as possible. Human Investigation Committee of Wayne State University. Scores arebased on thetimetocompletion. Journal of Aging Research 3 Table 1: Demographic, exercise, BMI and mood characteristics of Table 3: Frequencies of health conditions. sample. (Overall N = 106) Frequencies Percentage (Overall N = 106) Mean SD Range Hypertension 71 67% Age 71.83 7.73 56–91 Myocardial infarct 11 10% Education 12.74 2.45 6–18 Peripheral vascular disease 8 7% GDS-15 1.78 1.89 0–9 Diabetes 23 22% Exercise 2.75 2.61 0–7 Stroke 11 10% BMI 31.39 7.91 15.7–56.7 Congestive heart failure 11 10% Note: GDS: Geriatric Depression Scale-15 item; BMI: body mass index. Arthritis 76 72% Gastrointestinal disease 25 24% Table 2: Descriptive statistics for cognitive measures. Kidney disease 7 7% Liver disease 1 .9% Measure Mean SD Range COPD or emphysema 9 8% FOME 39.84 5.31 24–50 MMSE 27.05 2.18 19–30 Stroop Color/Word 25.15 9.63 2–49 in the Established Populations for Epidemiologic Studies TMT-A 56.21 27.02 20–136 of the Elderly (EPESE) studies that examined physical WASI BD 16.05 10.35 2–43 functioning in over 5,000 mostly white older adults [38]. This Note: FOME: Fuld Object Memory Evaluation; MMSE: Mini Mental Status methodology is described in detail elsewhere [3, 38]. Lower- Exam;TMT-A: Trail Making Test,Part A; WASI BD: Wechsler Abbreviated extremity function was assessed through the performance of Scale of Intelligence, Block Design subtest. three tasks: standing balance, walking, and chair stands. Balance was assessed by recording the amount of time each participant could maintain each of the following three Wechsler Abbreviated Scale of Intelligence (WASI), Block poses: semitandem (heel of one foot to the side of the first Design subtest [36]. The WASI Block Design subtest is a toe of the other foot), tandem (heel to toe), and side-by-side. timed measure of visuoconstructional abilities in which par- Timing stopped when the participant lost balance, grasped ticipants use blocks to construct three-dimensional figures for the examiner, or ten seconds had elapsed. According to from a two-dimensional drawing in the stimulus book. the Guralnik et al.’s criteria [38], participants received a score of a 1 if they were able to hold a side-by-side position for 10 2.4. Geriatric Depression Scale-15 Item (GDS) [37]. The seconds, but were unable to hold a semi-tandem position; a GDS-15 is a shortened version of the original 30-item score of a 2 if they could hold a semi-tandem position for 10 screening questionnaire that is presented verbally to the seconds but were unable to hold a full tandem for more than participant. Respondents answer yes or no to questions 2 seconds; a score of a 3 if they could stand in full tandem for regarding how they have felt over the last two weeks. Items for 3 to 9 seconds; and a score of a 4 if they could stand in full which a respondent indicates pathology are given a score of 1. tandem for 10 seconds. Total scores range from 0 to 15, with higher scores indicating Gait speed was assessed by two 3-meter walks, at a greater depressive symptomology. normal everyday pace, which was marked out for each subject in advance. The faster of their two walks was used 2.5. Exercise. Participation in exercise was obtained from as their final score which was recorded in quartiles such that self-reported answers to the following questions: (1) “Do ascore of 1 =≥ 5.6 seconds; a score of 2 = 4.4–5.5 seconds; a you participate in a regular program of exercise?” and if yes, score of 3 = 3.8–4.3 seconds; and a score of 4 =≤ 3.7. then “How many days per week”. Participants were asked to The final task, chair stands, required the participants to provide an estimated number of days between 0 and 7. fold their arms across their chest and to stand up from a sitting position once. Upon successful completion of this task, participants were asked to stand up and sit down with 2.6. Health. Participants were asked whether a doctor had ever told them that they have health conditions that were their armsacrosstheir chestfive times asquickly as they grouped into two disease categories: (1) cardiovascular (i.e., could. Times were then recorded into quartiles such that a score of a 1 =≥ 16.1 seconds; a score of a 2 = 12.9 to 16.0 hypertension, stroke, myocardial infarct, congestive heart failure, vascular disease, and diabetes), or (2) general health seconds; a score of a 3 = 9.9 to 12.8 seconds; and a score of a 4 =≤ 9.8 seconds. (i.e., arthritis, chronic obstructive pulmonary disease, gas- Summing the scores for each subtask (standing balance, trointenstinal conditions, kidney disease, and liver disease). Table 3 shows the number of participants that reported each gait speed, and chair rises) creates a summary performance score that was used in the analyses. of these health conditions. Participants were also asked to report their estimated current height and weight. 2.8. Statistical Methods. All statistical analyses were per- 2.7. Short Physical Performance Battery (SPPB). The SPPB formed using PASW Statistics 18 (SPSS Inc., 2009). Partic- used in this study was replicated from methodology used ipants who were missing data on variables of interest (n = 6) 4 Journal of Aging Research Table 4: Association of cognition with the SPPB. were excluded from the analyses. All variables were examined to ensure they met assumptions of normality. All variables Variable Beta SE Beta β Sig. ΔR except BMI were within acceptable ranges; a logarithmic Stroop C/W .07 .03 .21 .04 .03 transformation was performed on BMI. The transformed WASI BD .03 .03 .10 .32 .01 variable was used in all analyses. To initially ascertain the TMT-A −.02 .01 −.17 .09 .09 relationships between the SPPB and predictor variables, Pearson product moment correlations were obtained. To Note: Results are based on separate hierarchical regression models for each cognitive test. Block 2 adjusted for age, education and MMSE score. WASI examine the relationship between physical performance and BD: Wechsler Abbreviated Scale of Intelligence, Block Design subtest; TMT- specific domains of cognition, a multiple regression analysis A: Trail Making Test, Part A. was conducted in which SPPB total score was regressed on age, education, and MMSE. Each individual cognitive test significant predictors in Block 1. In Block 2, Stroop C/W (Stroop C/W, TMT-A, MMSE and WASI Block Design) significantly improved prediction of SPPB scores (P< .00); was entered into separate regression analyses. Raw scores ΔR = .05, F(1, 102) = 7.01, P< .00. With the addition of were used for all cognitive measures of interest. Next, to Stroop C/W, education became nonsignificant. In Block 3, examine the relationship between physical performance and exercise did not significantly improve prediction (P> .05); demographic variables (i.e., age, and education), cognition, ΔR = .02, F(1, 101) = 2.74, P = .10. GDS significantly exercise, mood, disease burden and BMI, a hierarchical improved prediction (P< .05) in Block 4; ΔR = .04, regression analysis was conducted. In Block 1, SPPB total F(1, 100) = 5.36, P< .05. In Block 5, both vascular health score was regressed on age and education. To examine the (P< .05) and general health were significant (P< .05); incremental variance accounted for by other variables of ΔR = .08, F(2, 98) = 5.93, P< .00. With the entry of the interest, Stroop C/W raw score was entered in Block 2, health variables in Block 5, the GDS became non-significant exercise was entered in Block 3, GDS total score was entered (P = .21). In Block 6, BMI was significant (P< .05); however, in Block 4, total number of both vascular health and general vascular and general health became non-significant (P> health conditions were entered in Block 5, and BMI was .05); ΔR = .03, F(1, 97) = 4.84, P< .03. In the final model, entered in Block 6. For both sets of analyses, a P value of less age, Stroop C/W, and BMI were significant contributors, and than .05 was considered significant. accounted for 32.8% (Adj. R ) of the variance in SPPB scores. Block 6 results are reported in Table 5. 3. Results Examination of preliminary analyses revealed significant 4. Discussion bivariate relationships between the SPPB and age (r =−.34; P< .00), education (r = .20; P< .04), BMI (r =−.27; Confirming our hypothesis, among cognitive domains of P< .00), exercise (r = .20; P< .05), vascular health memory, attention, and visuospatial construction, only exec- (r =−.29; P< .00), general health (r =−.25; P< .01), and utive functioning was significantly associated with physical the GDS (r =−.26,P< .01). All cognitive variables were also performance after controlling for general cognitive func- significantly correlated with SPPB performance (MMSE, r = tioning. A secondary analysis demonstrated that among a .29, P< .00; WASI BD, r = .24, P< .01; TMT-A, r =−.33, range of factors shown to contribute to disability onset, P< .00; Stroop C/W, r = .36, P< .00), except the FOME age, executive functioning, and BMI were associated with (r = .18, P = .07). physical performance scores. These findings have clinical To examine our first hypothesis, a multiple regression implications for improving gerontology’s understanding of was conducted to determine the association of each cognitive disability and helping clinicians and researchers to design domain (i.e., attention, visuospatial skills, and executive and implement interventions aimed at delaying disability functioning) with physical performance after accounting for onset among African American women. age, education, and general cognitive functioning (MMSE). Foremost, this study provides further evidence that In Block 1, age (P< .00) and MMSE (P< .05) significantly executive functioning contributes not only to ADL disability contributed to SPPB scores. Upon entry of each cognitive onset, but also to declines in physical performance, an early measure individually in Block 2, only Stroop C/W was indicator of disability, in African American older adults significantly associated with physical performance (P< .05). [1, 17, 39]. Executive functioning accounted for a small, yet MMSE was nonsignificant with the entry of Stroop C/W. significant, proportion of variance in physical performance, This model accounted for 18.8% of the variance in physical and our findings suggest that performance of basic physical performance scores; see Table 4 for results. tasks included in the SPPB involve executive processes Next, a hierarchical regression was conducted to ascertain such as inhibition and mental flexibility. An older adult’s the amount of variance in physical performance accounted ability to inhibit attention to extraneous information in the for by demographics, cognition, exercise, depression, vas- environment and to make appropriate responses is involved cular health, general health and BMI. Based on results of in the successful performance of physical tasks. Executive the initial analyses, only Stroop C/W was used to represent functions may become even more important in complex cognition in this model. R change was significant at Block scenarios older adults face in daily life, such as when avoiding 1with entry of demographics, R = .15, F(2, 103) = 9.39, obstacles in their home or when attempting to multitask (i.e., P< .00. Age (P< .00) and education (P< .05) were both walking and talking). Journal of Aging Research 5 Table 5: Contribution of demographics, cognition, depression, exercise and health variables to SPPB. Block 6 Beta Std. Error βt Sig. Age −.16 .04 −.32 −3.80 .00 Education .09 .12 .07 .76 .45 Stroop C/W .06 .03 .19 2.06 .04 Exercise .10 .11 .09 .97 .33 GDS −.20 .15 −.12 −1.33 .19 General health −.49 .30 −.15 −1.63 .11 Vascular health −.46 .26 −.15 −1.75 .08 BMI −6.24 2.83 −.20 −2.20 .03 Note: BMI: Body Mass Index; GDS: Geriatric Depression Scale. These findings are supported by and expand upon our dysfunction. Brain insult to shared neuroanatomical path- previous work using a separate dataset of African American ways secondary to CVRFs may partially explain mutual elders from the Detroit area [16]. In this study, two of three declines in cognition and physical performance. Supporting measures of executive functioning (Trail Making Test, Part B this hypothesis, Leung and colleagues [46]found that and Animal Naming) were significantly associated with SPPB Stroop performance was related to activation in the anterior scores after controlling for general cognitive functioning. The cingulate gyrus, as well as inferior and middle frontal regions; current study demonstrates that even after examination of areas implicated in physical performance tasks and sensitive four other domains of cognition, only executive functioning to the impact of vascular burden. Because the frontal lobe is associated with physical performance. Providing conver- integrates informational input from multiple regions of the gent evidence of this relationship in a similar study of African brain, WMHs and atrophy to shared pathways in the frontal American older adults, Nieto and colleagues [13]report region could result in both physical performance declines that after adjusting for age, gender, comorbidity, global and executive dysfunction. cognition, education levels, and global memory, individuals Exercise was not associated with physical performance with poor executive function were four times more likely to in our study. Previous work has demonstrated that exercise have impaired lower-extremity functioning. These results are interventions yield better performance on the SPPB [31, 47] congruent with several other studies reporting relationships when participants were engaged in moderate exercise for between executive functioning and physical performance in approximately 150 minutes per week. Our ability to find a samples of predominantly white older adults [14, 15, 40]. relationship between exercise and the SPPB may have been Executive functioning measures such as the Stroop are brief, attenuated by the amount and intensity of exercise of our easy to administer and are well tolerated by older adults. participants. Also, physical activity is difficult to accurately Disability assessment traditionally includes some measure of measure via self-report as older adults often participate in general cognition, often the MMSE. However, we argue that unstructured, low-intensity physical activities that can be the addition of executive function measures would improve difficult to recall [48]. One final consideration is that exercise assessment of disability risk. is a health behavior, while the variables that were significant Our second analysis provides further information about in the model, namely BMI and cognition, are the outcome of mechanisms potentially underlying the relationship between cumulative lifelong processes. BMI in particular likely reflects physical performance and executive functioning. Along lifelong health behaviors, including exercise. with executive functioning, age and BMI were significantly Though depression was not significantly related to associated with physical performance while mood and physical performance in the final model, it was a significant exercise were not. Although both vascular and general predictor prior to the entry of vascular and general health, health conditions were significantly associated with physical and is related to poorer physical performance in other studies performance, they became non-significant after entry of [15]. As such, disease burden may mediate the relationship BMI. BMI is a well-established risk factor for disability in between depression and physical performance [49]. The older adults [41]. Outcomes of and contributors to BMI and relationship between physical performance and depression obesity are difficult to separate; however, obesity is highly within samples of African American elders requires further associated with medical burden, particularly cardiovascular clarification. conditions and arthritis, as well as frailty and decreased There are several limitations to this study. Foremost, exercise tolerance and mobility [42]. Reciprocal influences due to our small sample size (N = 106), our findings of several processes lead to greater BMI and increase risk for should be considered exploratory in nature. Further work disability. Associations between vascular burden, obesity, and is needed to extend and support these findings within a both physical and cognitive declines is of particular interest larger sample of African American elders drawn from various [43–45]. geographic regions. Secondly, only single measures were Our results support the idea that vascular disease in used to represent each cognitive domain. Because the Stroop later life increases an older adult’s risk for physical declines, involves processing speed, as do SPPB tasks, it may be and that physical performance is associated with executive questioned whether the processing speed factor accounts 6 Journal of Aging Research for its association with the SPPB. 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Physical Performance Is Associated with Executive Functioning in Older African American Women

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Copyright © 2011 Brooke C. Schneider and Peter A. Lichtenberg. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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SAGE-Hindawi Access to Research Journal of Aging Research Volume 2011, Article ID 578609, 8 pages doi:10.4061/2011/578609 Research Article Physical Performance Is Associated with Executive Functioning in Older African American Women 1 2 Brooke C. Schneider and Peter A. Lichtenberg Psychology Service, VA Greater Los Angeles Healthcare Center, Los Angeles, CA 90073, USA Institute of Gerontology, Wayne State University, Detroit, Michigan 48202, USA Correspondence should be addressed to Brooke C. Schneider, schneider.brooke@gmail.com Received 1 September 2010; Revised 1 December 2010; Accepted 4 January 2011 Academic Editor: Iris Reuter Copyright © 2011 B. C. Schneider and P. A. Lichtenberg. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. An older adult’s ability to perform physical tasks is predictive of disability onset and is associated with declines in cognition. Risk factors for physical performance declines among African Americans, a group with the highest rates of disability, remain understudied. This study sought to identify demographic, health, and cognitive factors associated with lower-extremity physical performance in a sample of 106 African American women ages 56 to 91. After controlling for global cognitive functioning (Mini Mental State Exam), physical performance was associated with executive functioning (Stroop Color/Word), but not visuospatial construction (WASI Block Design) or processing speed (Trail Making Test, Part A). Executive functioning remained associated with physical performance after entry of demographic variables, exercise, depression, disease burden, and body mass index (BMI). Age, and BMI were also significant in this model. Executive functioning, age and BMI are associated with lower-extremity physical performance among older African American women. 1. Introduction than both white adults [4] and suburban African Americans [5]. Impairments in physical and cognitive functioning, as well While much evidence exists for the relationship between as onset of chronic diseases, are often feared in later life as cognitive functioning and ADL declines [6–8], fewer studies such changes lead to dependence in tasks of daily living, have focused on the associations between physical perfor- depression, and hospitalization. Compared to white elders, mance and cognition, specifically executive functioning, in African American older adults experience a greater number minority populations. Executive functioning encompasses of years exposed to the negative impacts of chronic disease a broad range of cognitive abilities such as the planning, and functional disability [1] making disability intervention sequencing, and execution of complex goal-directed behav- especially important for this minority group. The field of iors characteristic of IADLs (instrumental activities of daily gerontology has identified lower-extremity physical perfor- living) [9, 10]. Amongst cognitive domains such as mem- mance measures as key for identification of early changes ory, language, visuospatial ability, and psychomotor speed, that may lead to disability in older adults. Lower-extremity executive functioning is deemed as essential to preserved measures of physical performance are predictive of several functional status [11, 12]. Prior studies have found that outcomes in later life including declines in activities of daily executive functioning is related to mobility and balance living (ADLs), hospitalization, risk for death, nursing home among older adults [13–15]; however, this relationship placement, and hip fracture [2, 3]. Reflecting the observed may be attenuated after accounting for disease burden racial and socioeconomic discrepancies in rates of disability in African American elders [16]. Additionally, it remains among older adults, African American elders score more unclear whether performance of physical tasks may involve poorly on performance-based measures of physical function executive functioning more than other domains of cognition 2 Journal of Aging Research and whether screening measures of global cognitive func- Prior to participation, all participants provided signed tioning, such as the Mini Mental Status Exam (MMSE), consent. Subjects were recruited from independent living which are commonly used in disability risk assessments, centers, community centers and senior apartments through may adequately predict physical performance declines [14, presentations within the community given by the PI. Fliers 17, 18]. stating that the aim of the study is to understand “health Neuroimaging studies and clinical observation of age- and cognitive functioning in older African American adults” related cognitive disorders such as Parkinson’s disease and were also given to potential participants. Individuals were vascular dementia, provide evidence that changes in brain excluded if they (1) did not self-report as African American structures result in impairments in both cognitive function- or black; (2) were unable to speak English fluently; (3) had ing [9] and physical performance [19]. The frontal subcor- major hearing or vision loss; and/or (4) were below age tical region, implicated in tasks of executive functioning, is 55. Because the dataset contained a significantly greater particularly sensitive to effects of cardiovascular risk factors proportion of females (87.7%), male participants were (CVRFs) such as atherosclerosis, hypertension, stroke, and excluded from these analyses. diabetes [20–24]. Vascular burden is associated with presence A summary of participant characteristics is presented in of white matter hyperintensities (WMHs), brain atrophy Table 1 and mean raw scores on cognitive measures for the and infarcts. Older adults with compromise to the white final sample are presented in Table 2.The final sample was matter pathways connecting subcortical and frontal regions comprised of 106 African American women ages 56 to 91 secondary to vascular processes demonstrate poor executive (mean = 71.83; SD = 7.73), and with 6 to 18 years of formal functioning, slow gait speed and depression [15, 25]. The education (mean = 12.74; SD = 2.45). co-occurrence of these symptoms is associated with greater 2.2. Measures and Procedures. Measures reported in this functional dependency [19], poorer physical performance study were administered as part of a larger evaluation that [15], and mortality [26]. involved data collection on demographics, physical health, African American adults have higher body mass index cognition, health behaviors, and mental health in urban (BMI), and a greater number of health conditions, par- African American elders for a dissertation project. Data ticularly CVRFs such as hypertension and diabetes, when was collected in an individual interview session format by compared to their white, same-gender peers [27, 28]. Both three trained interviewers who were supervised by a research obesity and inactivity are associated with disability [29]. psychologist (PL). Participants were informed of the length Exercise interventions have been shown to improve scores on of the test battery prior to participation. However, due to measures of lower-extremity functioning [30]and decrease participant time restraints leading them to leave early or risk for mortality, frailty, disease [31]and obesity[29]; arrive late, as well as slowness in completing the measures, however, it remains unclear what level of exercise is needed the battery occasionally had to be shortened or terminated to decrease disability risk. In order to develop interventions before all measures were completed. This led to slight and delay disability onset within African American elders, a differences in sample size across measures. The average time high-risk group of older adults, further work is needed to to complete the battery was two hours. understand the impact of medical conditions and the poten- tial benefit of exercise to prevent early disability. The goals of this study are to (1) identify whether a spe- 2.3. Cognitive Measures. Fuld object memory evaluation cific domain of cognition versus global cognitive functioning (FOME) [32]. TheFOME is a measureof verbal memory may be uniquely associated with physical performance; and that involves recall of 10 common objects. Recall trials are (2) to examine relationships between physical performance separated by a distraction task to minimize the effects of and a range of factors associated with disability risk including short-term memory. cognition, depression, exercise, disease burden, BMI and Mini Mental Status Exam (MMSE) [33]. The MMSE is demographics in a sample of community-dwelling African an 11-item screening tool used to obtain an estimate of an American older women. Based on previous research it was individual’s global cognitive functioning and orientation to predicted that executive functioning would be significantly date,time, andplace.Scores range from 0 to30 with higher associated with physical performance while other domains scores indicating better cognitive functioning. of cognition would not and that physical performance would Stroop Color/Word subtest (Stroop C/W) [34]. The be related to demographics, depression, exercise, health, and Stroop C/W test is a measure of processing speed and mental cognition. flexibility. The Stroop test is comprised of three subtasks: color word naming, color naming, and naming the color of ink a color name is printed in. For example, saying “green” 2. Methods when the word “red” is printed in green ink. Third subtask 2.1. Sample. Participants were drawn from the Health, is an interference trial that requires inhibition and mental Disability and Cognitive Function in Urban African Amer- flexibility. Time to completion was recorded for each trial. ican Older Adults dataset, which includes 130 community- Trail Making Test, Part A (TMT-A) [35]. Part A of the dwelling African American adults between the ages of 55 TMT is a measure of attention and psychomotor processing and 100 who resided in the city of Detroit. This project speed in which participants are asked to connect numbers received approval from the Institutional Review Board, in numerical order (1-2-3 and so on) as quickly as possible. Human Investigation Committee of Wayne State University. Scores arebased on thetimetocompletion. Journal of Aging Research 3 Table 1: Demographic, exercise, BMI and mood characteristics of Table 3: Frequencies of health conditions. sample. (Overall N = 106) Frequencies Percentage (Overall N = 106) Mean SD Range Hypertension 71 67% Age 71.83 7.73 56–91 Myocardial infarct 11 10% Education 12.74 2.45 6–18 Peripheral vascular disease 8 7% GDS-15 1.78 1.89 0–9 Diabetes 23 22% Exercise 2.75 2.61 0–7 Stroke 11 10% BMI 31.39 7.91 15.7–56.7 Congestive heart failure 11 10% Note: GDS: Geriatric Depression Scale-15 item; BMI: body mass index. Arthritis 76 72% Gastrointestinal disease 25 24% Table 2: Descriptive statistics for cognitive measures. Kidney disease 7 7% Liver disease 1 .9% Measure Mean SD Range COPD or emphysema 9 8% FOME 39.84 5.31 24–50 MMSE 27.05 2.18 19–30 Stroop Color/Word 25.15 9.63 2–49 in the Established Populations for Epidemiologic Studies TMT-A 56.21 27.02 20–136 of the Elderly (EPESE) studies that examined physical WASI BD 16.05 10.35 2–43 functioning in over 5,000 mostly white older adults [38]. This Note: FOME: Fuld Object Memory Evaluation; MMSE: Mini Mental Status methodology is described in detail elsewhere [3, 38]. Lower- Exam;TMT-A: Trail Making Test,Part A; WASI BD: Wechsler Abbreviated extremity function was assessed through the performance of Scale of Intelligence, Block Design subtest. three tasks: standing balance, walking, and chair stands. Balance was assessed by recording the amount of time each participant could maintain each of the following three Wechsler Abbreviated Scale of Intelligence (WASI), Block poses: semitandem (heel of one foot to the side of the first Design subtest [36]. The WASI Block Design subtest is a toe of the other foot), tandem (heel to toe), and side-by-side. timed measure of visuoconstructional abilities in which par- Timing stopped when the participant lost balance, grasped ticipants use blocks to construct three-dimensional figures for the examiner, or ten seconds had elapsed. According to from a two-dimensional drawing in the stimulus book. the Guralnik et al.’s criteria [38], participants received a score of a 1 if they were able to hold a side-by-side position for 10 2.4. Geriatric Depression Scale-15 Item (GDS) [37]. The seconds, but were unable to hold a semi-tandem position; a GDS-15 is a shortened version of the original 30-item score of a 2 if they could hold a semi-tandem position for 10 screening questionnaire that is presented verbally to the seconds but were unable to hold a full tandem for more than participant. Respondents answer yes or no to questions 2 seconds; a score of a 3 if they could stand in full tandem for regarding how they have felt over the last two weeks. Items for 3 to 9 seconds; and a score of a 4 if they could stand in full which a respondent indicates pathology are given a score of 1. tandem for 10 seconds. Total scores range from 0 to 15, with higher scores indicating Gait speed was assessed by two 3-meter walks, at a greater depressive symptomology. normal everyday pace, which was marked out for each subject in advance. The faster of their two walks was used 2.5. Exercise. Participation in exercise was obtained from as their final score which was recorded in quartiles such that self-reported answers to the following questions: (1) “Do ascore of 1 =≥ 5.6 seconds; a score of 2 = 4.4–5.5 seconds; a you participate in a regular program of exercise?” and if yes, score of 3 = 3.8–4.3 seconds; and a score of 4 =≤ 3.7. then “How many days per week”. Participants were asked to The final task, chair stands, required the participants to provide an estimated number of days between 0 and 7. fold their arms across their chest and to stand up from a sitting position once. Upon successful completion of this task, participants were asked to stand up and sit down with 2.6. Health. Participants were asked whether a doctor had ever told them that they have health conditions that were their armsacrosstheir chestfive times asquickly as they grouped into two disease categories: (1) cardiovascular (i.e., could. Times were then recorded into quartiles such that a score of a 1 =≥ 16.1 seconds; a score of a 2 = 12.9 to 16.0 hypertension, stroke, myocardial infarct, congestive heart failure, vascular disease, and diabetes), or (2) general health seconds; a score of a 3 = 9.9 to 12.8 seconds; and a score of a 4 =≤ 9.8 seconds. (i.e., arthritis, chronic obstructive pulmonary disease, gas- Summing the scores for each subtask (standing balance, trointenstinal conditions, kidney disease, and liver disease). Table 3 shows the number of participants that reported each gait speed, and chair rises) creates a summary performance score that was used in the analyses. of these health conditions. Participants were also asked to report their estimated current height and weight. 2.8. Statistical Methods. All statistical analyses were per- 2.7. Short Physical Performance Battery (SPPB). The SPPB formed using PASW Statistics 18 (SPSS Inc., 2009). Partic- used in this study was replicated from methodology used ipants who were missing data on variables of interest (n = 6) 4 Journal of Aging Research Table 4: Association of cognition with the SPPB. were excluded from the analyses. All variables were examined to ensure they met assumptions of normality. All variables Variable Beta SE Beta β Sig. ΔR except BMI were within acceptable ranges; a logarithmic Stroop C/W .07 .03 .21 .04 .03 transformation was performed on BMI. The transformed WASI BD .03 .03 .10 .32 .01 variable was used in all analyses. To initially ascertain the TMT-A −.02 .01 −.17 .09 .09 relationships between the SPPB and predictor variables, Pearson product moment correlations were obtained. To Note: Results are based on separate hierarchical regression models for each cognitive test. Block 2 adjusted for age, education and MMSE score. WASI examine the relationship between physical performance and BD: Wechsler Abbreviated Scale of Intelligence, Block Design subtest; TMT- specific domains of cognition, a multiple regression analysis A: Trail Making Test, Part A. was conducted in which SPPB total score was regressed on age, education, and MMSE. Each individual cognitive test significant predictors in Block 1. In Block 2, Stroop C/W (Stroop C/W, TMT-A, MMSE and WASI Block Design) significantly improved prediction of SPPB scores (P< .00); was entered into separate regression analyses. Raw scores ΔR = .05, F(1, 102) = 7.01, P< .00. With the addition of were used for all cognitive measures of interest. Next, to Stroop C/W, education became nonsignificant. In Block 3, examine the relationship between physical performance and exercise did not significantly improve prediction (P> .05); demographic variables (i.e., age, and education), cognition, ΔR = .02, F(1, 101) = 2.74, P = .10. GDS significantly exercise, mood, disease burden and BMI, a hierarchical improved prediction (P< .05) in Block 4; ΔR = .04, regression analysis was conducted. In Block 1, SPPB total F(1, 100) = 5.36, P< .05. In Block 5, both vascular health score was regressed on age and education. To examine the (P< .05) and general health were significant (P< .05); incremental variance accounted for by other variables of ΔR = .08, F(2, 98) = 5.93, P< .00. With the entry of the interest, Stroop C/W raw score was entered in Block 2, health variables in Block 5, the GDS became non-significant exercise was entered in Block 3, GDS total score was entered (P = .21). In Block 6, BMI was significant (P< .05); however, in Block 4, total number of both vascular health and general vascular and general health became non-significant (P> health conditions were entered in Block 5, and BMI was .05); ΔR = .03, F(1, 97) = 4.84, P< .03. In the final model, entered in Block 6. For both sets of analyses, a P value of less age, Stroop C/W, and BMI were significant contributors, and than .05 was considered significant. accounted for 32.8% (Adj. R ) of the variance in SPPB scores. Block 6 results are reported in Table 5. 3. Results Examination of preliminary analyses revealed significant 4. Discussion bivariate relationships between the SPPB and age (r =−.34; P< .00), education (r = .20; P< .04), BMI (r =−.27; Confirming our hypothesis, among cognitive domains of P< .00), exercise (r = .20; P< .05), vascular health memory, attention, and visuospatial construction, only exec- (r =−.29; P< .00), general health (r =−.25; P< .01), and utive functioning was significantly associated with physical the GDS (r =−.26,P< .01). All cognitive variables were also performance after controlling for general cognitive func- significantly correlated with SPPB performance (MMSE, r = tioning. A secondary analysis demonstrated that among a .29, P< .00; WASI BD, r = .24, P< .01; TMT-A, r =−.33, range of factors shown to contribute to disability onset, P< .00; Stroop C/W, r = .36, P< .00), except the FOME age, executive functioning, and BMI were associated with (r = .18, P = .07). physical performance scores. These findings have clinical To examine our first hypothesis, a multiple regression implications for improving gerontology’s understanding of was conducted to determine the association of each cognitive disability and helping clinicians and researchers to design domain (i.e., attention, visuospatial skills, and executive and implement interventions aimed at delaying disability functioning) with physical performance after accounting for onset among African American women. age, education, and general cognitive functioning (MMSE). Foremost, this study provides further evidence that In Block 1, age (P< .00) and MMSE (P< .05) significantly executive functioning contributes not only to ADL disability contributed to SPPB scores. Upon entry of each cognitive onset, but also to declines in physical performance, an early measure individually in Block 2, only Stroop C/W was indicator of disability, in African American older adults significantly associated with physical performance (P< .05). [1, 17, 39]. Executive functioning accounted for a small, yet MMSE was nonsignificant with the entry of Stroop C/W. significant, proportion of variance in physical performance, This model accounted for 18.8% of the variance in physical and our findings suggest that performance of basic physical performance scores; see Table 4 for results. tasks included in the SPPB involve executive processes Next, a hierarchical regression was conducted to ascertain such as inhibition and mental flexibility. An older adult’s the amount of variance in physical performance accounted ability to inhibit attention to extraneous information in the for by demographics, cognition, exercise, depression, vas- environment and to make appropriate responses is involved cular health, general health and BMI. Based on results of in the successful performance of physical tasks. Executive the initial analyses, only Stroop C/W was used to represent functions may become even more important in complex cognition in this model. R change was significant at Block scenarios older adults face in daily life, such as when avoiding 1with entry of demographics, R = .15, F(2, 103) = 9.39, obstacles in their home or when attempting to multitask (i.e., P< .00. Age (P< .00) and education (P< .05) were both walking and talking). Journal of Aging Research 5 Table 5: Contribution of demographics, cognition, depression, exercise and health variables to SPPB. Block 6 Beta Std. Error βt Sig. Age −.16 .04 −.32 −3.80 .00 Education .09 .12 .07 .76 .45 Stroop C/W .06 .03 .19 2.06 .04 Exercise .10 .11 .09 .97 .33 GDS −.20 .15 −.12 −1.33 .19 General health −.49 .30 −.15 −1.63 .11 Vascular health −.46 .26 −.15 −1.75 .08 BMI −6.24 2.83 −.20 −2.20 .03 Note: BMI: Body Mass Index; GDS: Geriatric Depression Scale. These findings are supported by and expand upon our dysfunction. Brain insult to shared neuroanatomical path- previous work using a separate dataset of African American ways secondary to CVRFs may partially explain mutual elders from the Detroit area [16]. In this study, two of three declines in cognition and physical performance. Supporting measures of executive functioning (Trail Making Test, Part B this hypothesis, Leung and colleagues [46]found that and Animal Naming) were significantly associated with SPPB Stroop performance was related to activation in the anterior scores after controlling for general cognitive functioning. The cingulate gyrus, as well as inferior and middle frontal regions; current study demonstrates that even after examination of areas implicated in physical performance tasks and sensitive four other domains of cognition, only executive functioning to the impact of vascular burden. Because the frontal lobe is associated with physical performance. Providing conver- integrates informational input from multiple regions of the gent evidence of this relationship in a similar study of African brain, WMHs and atrophy to shared pathways in the frontal American older adults, Nieto and colleagues [13]report region could result in both physical performance declines that after adjusting for age, gender, comorbidity, global and executive dysfunction. cognition, education levels, and global memory, individuals Exercise was not associated with physical performance with poor executive function were four times more likely to in our study. Previous work has demonstrated that exercise have impaired lower-extremity functioning. These results are interventions yield better performance on the SPPB [31, 47] congruent with several other studies reporting relationships when participants were engaged in moderate exercise for between executive functioning and physical performance in approximately 150 minutes per week. Our ability to find a samples of predominantly white older adults [14, 15, 40]. relationship between exercise and the SPPB may have been Executive functioning measures such as the Stroop are brief, attenuated by the amount and intensity of exercise of our easy to administer and are well tolerated by older adults. participants. Also, physical activity is difficult to accurately Disability assessment traditionally includes some measure of measure via self-report as older adults often participate in general cognition, often the MMSE. However, we argue that unstructured, low-intensity physical activities that can be the addition of executive function measures would improve difficult to recall [48]. One final consideration is that exercise assessment of disability risk. is a health behavior, while the variables that were significant Our second analysis provides further information about in the model, namely BMI and cognition, are the outcome of mechanisms potentially underlying the relationship between cumulative lifelong processes. BMI in particular likely reflects physical performance and executive functioning. Along lifelong health behaviors, including exercise. with executive functioning, age and BMI were significantly Though depression was not significantly related to associated with physical performance while mood and physical performance in the final model, it was a significant exercise were not. Although both vascular and general predictor prior to the entry of vascular and general health, health conditions were significantly associated with physical and is related to poorer physical performance in other studies performance, they became non-significant after entry of [15]. As such, disease burden may mediate the relationship BMI. BMI is a well-established risk factor for disability in between depression and physical performance [49]. The older adults [41]. Outcomes of and contributors to BMI and relationship between physical performance and depression obesity are difficult to separate; however, obesity is highly within samples of African American elders requires further associated with medical burden, particularly cardiovascular clarification. conditions and arthritis, as well as frailty and decreased There are several limitations to this study. Foremost, exercise tolerance and mobility [42]. Reciprocal influences due to our small sample size (N = 106), our findings of several processes lead to greater BMI and increase risk for should be considered exploratory in nature. Further work disability. Associations between vascular burden, obesity, and is needed to extend and support these findings within a both physical and cognitive declines is of particular interest larger sample of African American elders drawn from various [43–45]. geographic regions. Secondly, only single measures were Our results support the idea that vascular disease in used to represent each cognitive domain. Because the Stroop later life increases an older adult’s risk for physical declines, involves processing speed, as do SPPB tasks, it may be and that physical performance is associated with executive questioned whether the processing speed factor accounts 6 Journal of Aging Research for its association with the SPPB. 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