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Ambulance calls to suspected overdoses: New South Wales patterns July 1997 to June 1999

Ambulance calls to suspected overdoses: New South Wales patterns July 1997 to June 1999 National Drug and Alcohol Research Centre, University of New South Wales Abstract Aim: Using data on New South Wales ambulance calls to suspected overdoses from July 1997 to June 1999 to: a) examine temporal and geog raphic trends in calls; and b) compare geographic patterns of fatal and non-fatal opioid overdose. Barbara-Ann Adelstein New South Wales Ambulance Ser vice here has been a considerable in crease in the rate of opioid overdose deaths in Australia over the past three decades,1 from 1.3 per 100,000 population among those aged 15-44 years in 1964 to 112.5 per 100,000 population in 1999. Half of these deaths occurred in New South Wales.2 Non-fatal opioid overdoses are more common events: around two-thirds (68%) of regular heroin users in Sydney report a nonfatal overdose at some time in their lives and 43% within the past year.3 An ambulance is called to around half (56%) of non-fatal overdoses.4 The number of opioid overdoses attended by ambulance officers may therefore provide an indication of trends in opioid use in the community and their location may provide an indication of geographic areas in which opioid use is common. Notably, persons may not overdose in the place where they live, so ambulance callouts provide infor mation on clustering of overdoses irrespective of the person’s place of residence. This paper e xamines data on ambulance calls in NSW to suspected overdoses between July 1997 and June 1999 to: • examine temporal and geographic trends; and • compare geographic data on ambulance attendances with data on fatal heroin overdose deaths in NSW . completed by ambulance officers on all patients treated from 1 July 1997 to 30 June 1999. They are based on the number of cases where ambulance officers have used the Ambulance Ser vice protocol for drug overdose/ poisoning and where naloxone was administered. Cases in which naloxone was not used for persons who had overdosed on heroin are not included. The drug overdose/ poisoning protocol includes all dr ug over doses and does not distinguish between the drugs used by the patient and naloxone may be administered to unconscious patients who have not responded to other treatment. The data are based on attendances at incidents rather than persons, which means that the same person may have accounted for several ambulance calls. Nonetheless, if we assume that these sources of er ror remain relatively constant over time and across areas, these data provide potentially useful infor mation on trends in non-fatal overdose and indirectly on opioid use. Fatal heroin overdoses used as the refer ence data source were determined by hand searches of complete coronial data files by Dr Shane Darke. Details may be obtained from publications including this data.5,6 Method: The NSW Ambulance Service provided data on the occasions when an ambulance attended a person on whom the drug overdose/poisonings protocol was used, and to whom naloxone was administered. The geographic distribution of ambulance attendances was approximated to the Australian Bureau of Statistics Statistical Local Area (SLA) and Statistical Subdivision (SSD). Estimates of social disadvantage were correlated with the rate of ambulance attendances for each region. Results : 9,116 callouts were made. In cases with data on age and gender, 89% were aged 15-44 years, and 31% were female. South Sydney (n=1,819) and Liverpool (n=1,602) SLAs accounted for 37% of calls; the higher rates outside Sydney were in Newcastle, Orange and Kiama. There was a strong correlation between rates of ambulance callouts and fatal heroin overdoses. The n umber of calls increased from an average of 361 calls per month in 1997-98 to 399 in 1998-99. The majority of calls (54%) were made between midday and 9pm. Conclusions: Rates of ambulance attendance at suspected overdoses is a promising indicator that allows monitoring of trends and identification of areas with high rates of opioid use. (Aust N Z J Public Health 2001; 25: 447-50) Data analysis Cases who were aged between 15 and 44 years were used in the current analyses to estimate rates of ambulance callouts according to Statistical Subdivision (SSD) area (see below). In this estimation, cases in whom no age was recorded were also included in this group, as previous research has sug- Method Data used in the current study The data come from case repor ts Correspondence to: Louisa Degenhardt, National Drug and Alcohol Research Centre, University of New South Wales, New South Wales 2052. Fax: (02) 9399 7143; e-mail: l.degenhardt@unsw.edu.au Submitted: August 2000 Revision requested: April 2001 Accepted: August 2001 2001 VOL. 25 NO . 5 AUSTRALIAN AND NEW ZEALAND JOURNAL OF PUBLIC HEALTH Degenhardt, Hall and Adelstein Article gested that by far the majority of opioid overdoses occur within this age group.7,8 In analysing the geographic distribution of ambulance attendances postcodes were matched to postal area using the Telstra White Pages inter net directory and the postal areas were then approximated to the 168 Statistical Local Areas (SLAs) and 43 Statistical Subdivisions (SSDs) used by the Australian Bureau of Statistics (ABS). To allow comparisons with the geographic location of fatal heroin overdoses in NSW,5,6 SSDs outside the Sydney area in which fatal heroin overdoses were v ery uncommon were aggre gated into: Newcastle-Hunter, New England, Mid West NSW, Southern NSW, Far West NSW South Coast, and Mid, North Coast. Rates per 100,000 population in each area were estimated using ABS estimates of the population in the 1996 Census.9 Furthermore, Standardised Rate Ratios (SRR) were calculated for each of these areas as an indication of how common ambulance callouts were when standardised according to residential population in each area. Estimates of relative social disadvantage for each area were obtained from 1996 ABS Census data. poisoning protocol was used and naloxone administered between July 1997 to June 1999. In the cases w here the age and gender data were recorded, 31% of cases were female, 89% were aged 15-44 years and 95% were between 15 and 54 years. These estimates are approximate because age was not recorded in 57.0% of cases and gender in 51.9% of cases. No relationship existed between these missing data and the area of the callout. Geographic distribution of ambulance calls to overdoses The two most common SLAs to which ambulances were called out to attend an overdose were South Sydney (n=1,819) and Liverpool (n=1,602), which together accounted for 37% of all calls (20.0% for South Sydney, 17.6% for Liver pool; see Table 1). Outside Sydney, the SLAs with higher rates were Newcastle with an average annual rate of 152 per 100,000, Orange with a rate of 126 and Kiama with a rate of 171 (see Table 1). The statistical subdivisions with the highest rates in Sydney were Inner Sydney (990) and Fairf ield Liver pool (631), with Newcastle-Hunter (111), Gosford (114), and Wollongong (149) recording the highest rates outside Sydney. Over the whole state, the correlation between social disadvantage and the ambulance attendance rate was r= –0.21, indicating that higher rates occurred in more disadvantaged areas. In Results There were 9,116 calls in which the ambulance drug overdose/ Table 1: Number of ambulance attendances 1997-99, population size, average rate per year rate per 100,000 population (all ages), and standardised rate ratios, by statistical local area (data for the 25 highest SLAs only). Statistical Local Area Sydney – inner South Sydney Botany Liverpool Sydney – remainder Marrickville Kiama Newcastle inner Orange Wollondilly Auburn Baranald Goulbur n Inverell Bathurst Leichhardt Penrith Greater Lithgow Manly Tweed Tamworth Strathfield Wollongong Fairfield Lismore Total (State) Number 1997-99 164 1819 519 1602 67 294 63 417 88 85 130 7 49 10 58 119 281 32 60 62 56 42 272 275 59 9,116 Population 3,732 79,460 35,938 124,292 10,114 79,876 18,374 137,265 34,828 34,583 53,266 2,934 21,490 4,622 29,146 60,749 167,868 19,994 37,703 39,148 35,580 27,170 183,497 189,108 43,551 6,295,368 Rate per year SRR 30.2 15.7 9.9 8.9 4.5 2.5 2.4 2.1 1.7 1.7 1.7 1.6 1.6 1.5 1.4 1.3 1.1 1.1 1.1 1.1 1.1 1.1 1.0 1.0 0.9 1.0 25.7 15.0 9.1 8.4 3.5 2.2 1.8 1.9 1.4 1.3 1.4 0.6 1.2 0.7 1.0 1.1 1.0 0.8 0.8 0.8 0.8 0.8 0.9 0.9 0.7 – 95% CI 35.2 16.5 10.8 9.3 5.8 2.8 3.0 2.3 2.1 2.1 2.0 3.4 2.1 2.7 1.8 1.6 1.3 1.6 1.4 1.4 1.4 1.4 1.1 1.1 1.2 – AUSTRALIAN AND NEW ZEALAND JOURNAL OF PUBLIC HEALTH VOL. 25 NO. 5 Vulnerable Groups Ambulance calls to suspected overdoses Sydney, the correlation was –0.46 but outside Sydney it was +0.21, indicating that there were higher rates of call outs in more advantaged (and perhaps more urbanised) areas. because data on amb ulance attendances was not available for the same period. Time of day of ambulance callouts Comparison of fatal heroin overdose and ambulance call rates Table 2 shows that the areas with the highest rates of ambulance attendances were those with highest rates of heroin overdose death. Inner Sydney recorded the highest rate per year of overdose deaths (37.0) and ambulance attendances (990.0), with Fairf ield-Liver pool recording the next highest rates (17.8 for fatal overdoses; 630.6 for ambulance attendances). Outside Sydney, Wollongong had the highest rate of heroin overdoses (7.7) and the highest ambulance attendance rate (148.6). The correlation between rates of fatal heroin overdose and ambulance attendances was r=+0.91. The relationship was stronger for Sydney areas (r=0.94) than for other areas in the state (r=0.48). The latter probably reflects the smaller number of deaths and hence greater variability in rates in areas with small populations; ambulance callout data may be less accurate as an indicator of opioid use outside major urban centres. These strong relationships were observed despite the fact that the heroin overdose data were recorded in 1992-96 rather than 1997-99 for ambulance attendances, The time of day at which ambulances were called to suspected overdoses was grouped in three-hour blocks; the distribution is displayed in Figure 1. The majority of calls (54%) were made between midday and 9pm. Calls were least likely to be made between midnight and 9am (19%). Discussion A large number of calls were made by the NSW Ambulance Service to suspected dr ug overdoses between July 1997 and June 1999: 4,300 in 1997-8, and almost 4,800 in 1998-9, with averages of 361 and 399 per month, respectively. This monthly average is higher than that estimated from a similar analysis of amb ulance calls in Victoria, where there was an average of 129 per month between November 1997 and January 1998 10 but differences in case ascertainment between the two data sources may limit comparisons. Greater consistency is needed between data in different States to permit comparisons. The data presented in the present paper are not approximates Table 2: Number of ambulance calls 1997-99, average rate per y ear among 15-44 year olds, and standardised rate ratios (SRR) by statistical subdivisions, and rate of fatal her oin overdose per year by statistical subdivision. Statistical Subdivision Number of callouts 1997-99 2,915 1,849 326 271 159 318 235 510 217 146 228 44 199 87 249 177 126 108 131 93 101 56 34 19 8,598 Rate per year Expected number 472 470 352 320 220 443 331 739 377 255 417 81 376 192 557 408 300 310 413 404 524 310 202 128 8,598 SRR 95% CI Fatal overdose average rate per year 1992-96 6.4 4.1 1.0 1.0 0.8 0.8 0.8 0.8 0.7 0.7 0.6 0.7 0.6 0.6 0.5 0.5 0.5 0.4 0.4 0.3 0.2 0.2 0.2 0.2 – 37.0 17.8 7.7 6.6 8.9 2.8 3.4 3.0 2.7 6.0 5.7 13.1 13.2 1.6 3.8 6.4 6.6 1.0 3.4 1.0 1.2 1.7 2.9 1.4 6.8 Inner Sydney Fairfield Liver pool Wollongong Outer South West Sydney Inner West Sydney Outer West Sydney Gosford Wyong Newcastle Hunter Mid West NSW Far Nor th Coast Canterbury Bankstown Southern Highlands Eastern Suburbs New England St George Sutherland Central West Sydney Northern Beaches Mid North Coast Lower Nor th Sydney Southern NSW Blacktown-Baulkham Hills Hornsby Kuringai South Coast Far West NSW Total (State) 6.0 3.8 0.8 0.8 0.6 0.6 0.6 0.6 0.5 0.5 0.5 0.4 0.5 0.4 0.4 0.4 0.4 0.3 0.3 0.2 0.2 0.1 0.1 0.1 – 2001 VOL. 25 NO . 5 AUSTRALIAN AND NEW ZEALAND JOURNAL OF PUBLIC HEALTH Degenhardt, Hall and Adelstein Article 20 18 16 14 12 10 8 6 4 2 0 12am - 3am6am- 9am- 12pm- 3p - 6p - 9p m m m 2:59am 5:59am 8:59am 11:59pm 2:59p 5:59p 8:59p 11:59am m m m Figure 1: Distribution of ambulance callouts by time of day. For all their limitations, the consistency of the ambulance data with other data on the characteristics of heroin users and the geographic and temporal distribution of fatal opioid overdoses is impressive. The agreement is all the more impressive given the smaller numbers of overdose deaths in some areas and the fact that the data covered two non-overlapping time periods. However, given the lower cor relation between fatal heroin overdoses and ambulance callouts in small non-urban areas, other indicator data may be better indicators of trends in these areas. These findings suggest that data on rates of ambulance attendance at suspected opioid overdoses constitute an additional promising indicator for monitoring trends in non-fatal opioid overdoses and indirectly, of opioid use. for the total number of non-fatal overdoses that occurred in NSW in the period (since only around half of non-fatal overdoses will involve an ambulance being called4), b ut they cer tainly allow observation of trends over time in the numbers of persons who were attended. This permits us to examine time trends in this proxy measure. While public health campaigns (such as those to increase calls to ambulances in cases of suspected overdose) may affect the likelihood of calling an ambulance, heroin use had a high profile over the whole period in which this data was collected and effor ts to increase ambulance call outs to suspected over doses began in 1997. The main trends were clear and consistent with other data. First, when gender was recorded it was female in a third of cases. This is higher than the 20% of females among opioid overdose deaths 11 but similar to the proportion of females in the methadone maintenance treatment (MMT)12,13 in IDU samples 14 and among needle and syringe programs attendees (NSP).15 Persons who have over dosed and been attended by ambulances may be more representative of the opioid using population than overdose fatalities. Second, most ambulance attendances and fatal opioid overdose deaths7,8 occur among persons aged 15-44 years, and most often in those aged 25-34 years. Although these patterns are consistent with what is known about the characteristics of heroin users, we do not know the age and gender of about half of the sample. Third, the majority of ambulance callouts occurred in Sydney and other large cities. The two SLAs with the highest rates were Liverpool and South Sydney, the areas in which the largest NSW heroin markets are concentrated.16 Fatal heroin overdose deaths and ambulance callouts were concentrated in the same geographic areas, par ticularly in Sydney; this clustering indicates where use occurred rather than where persons resided. Fourth, the time of day of callouts is similar to that for heroin fatalities in NSW.17,18 In South Western Sydney between 1992 and 1996, 37% of deaths were estimated to occur between midday and 6pm18 and 37% of ambulance calls were made within this period. This pattern is similar to that in ambulance callouts in Victoria,10 the ACT19 and Germany.20 percentage http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Australian and New Zealand Journal of Public Health Wiley

Ambulance calls to suspected overdoses: New South Wales patterns July 1997 to June 1999

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Publisher
Wiley
Copyright
Copyright © 2001 Wiley Subscription Services, Inc., A Wiley Company
ISSN
1326-0200
eISSN
1753-6405
DOI
10.1111/j.1467-842X.2001.tb00291.x
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Abstract

National Drug and Alcohol Research Centre, University of New South Wales Abstract Aim: Using data on New South Wales ambulance calls to suspected overdoses from July 1997 to June 1999 to: a) examine temporal and geog raphic trends in calls; and b) compare geographic patterns of fatal and non-fatal opioid overdose. Barbara-Ann Adelstein New South Wales Ambulance Ser vice here has been a considerable in crease in the rate of opioid overdose deaths in Australia over the past three decades,1 from 1.3 per 100,000 population among those aged 15-44 years in 1964 to 112.5 per 100,000 population in 1999. Half of these deaths occurred in New South Wales.2 Non-fatal opioid overdoses are more common events: around two-thirds (68%) of regular heroin users in Sydney report a nonfatal overdose at some time in their lives and 43% within the past year.3 An ambulance is called to around half (56%) of non-fatal overdoses.4 The number of opioid overdoses attended by ambulance officers may therefore provide an indication of trends in opioid use in the community and their location may provide an indication of geographic areas in which opioid use is common. Notably, persons may not overdose in the place where they live, so ambulance callouts provide infor mation on clustering of overdoses irrespective of the person’s place of residence. This paper e xamines data on ambulance calls in NSW to suspected overdoses between July 1997 and June 1999 to: • examine temporal and geographic trends; and • compare geographic data on ambulance attendances with data on fatal heroin overdose deaths in NSW . completed by ambulance officers on all patients treated from 1 July 1997 to 30 June 1999. They are based on the number of cases where ambulance officers have used the Ambulance Ser vice protocol for drug overdose/ poisoning and where naloxone was administered. Cases in which naloxone was not used for persons who had overdosed on heroin are not included. The drug overdose/ poisoning protocol includes all dr ug over doses and does not distinguish between the drugs used by the patient and naloxone may be administered to unconscious patients who have not responded to other treatment. The data are based on attendances at incidents rather than persons, which means that the same person may have accounted for several ambulance calls. Nonetheless, if we assume that these sources of er ror remain relatively constant over time and across areas, these data provide potentially useful infor mation on trends in non-fatal overdose and indirectly on opioid use. Fatal heroin overdoses used as the refer ence data source were determined by hand searches of complete coronial data files by Dr Shane Darke. Details may be obtained from publications including this data.5,6 Method: The NSW Ambulance Service provided data on the occasions when an ambulance attended a person on whom the drug overdose/poisonings protocol was used, and to whom naloxone was administered. The geographic distribution of ambulance attendances was approximated to the Australian Bureau of Statistics Statistical Local Area (SLA) and Statistical Subdivision (SSD). Estimates of social disadvantage were correlated with the rate of ambulance attendances for each region. Results : 9,116 callouts were made. In cases with data on age and gender, 89% were aged 15-44 years, and 31% were female. South Sydney (n=1,819) and Liverpool (n=1,602) SLAs accounted for 37% of calls; the higher rates outside Sydney were in Newcastle, Orange and Kiama. There was a strong correlation between rates of ambulance callouts and fatal heroin overdoses. The n umber of calls increased from an average of 361 calls per month in 1997-98 to 399 in 1998-99. The majority of calls (54%) were made between midday and 9pm. Conclusions: Rates of ambulance attendance at suspected overdoses is a promising indicator that allows monitoring of trends and identification of areas with high rates of opioid use. (Aust N Z J Public Health 2001; 25: 447-50) Data analysis Cases who were aged between 15 and 44 years were used in the current analyses to estimate rates of ambulance callouts according to Statistical Subdivision (SSD) area (see below). In this estimation, cases in whom no age was recorded were also included in this group, as previous research has sug- Method Data used in the current study The data come from case repor ts Correspondence to: Louisa Degenhardt, National Drug and Alcohol Research Centre, University of New South Wales, New South Wales 2052. Fax: (02) 9399 7143; e-mail: l.degenhardt@unsw.edu.au Submitted: August 2000 Revision requested: April 2001 Accepted: August 2001 2001 VOL. 25 NO . 5 AUSTRALIAN AND NEW ZEALAND JOURNAL OF PUBLIC HEALTH Degenhardt, Hall and Adelstein Article gested that by far the majority of opioid overdoses occur within this age group.7,8 In analysing the geographic distribution of ambulance attendances postcodes were matched to postal area using the Telstra White Pages inter net directory and the postal areas were then approximated to the 168 Statistical Local Areas (SLAs) and 43 Statistical Subdivisions (SSDs) used by the Australian Bureau of Statistics (ABS). To allow comparisons with the geographic location of fatal heroin overdoses in NSW,5,6 SSDs outside the Sydney area in which fatal heroin overdoses were v ery uncommon were aggre gated into: Newcastle-Hunter, New England, Mid West NSW, Southern NSW, Far West NSW South Coast, and Mid, North Coast. Rates per 100,000 population in each area were estimated using ABS estimates of the population in the 1996 Census.9 Furthermore, Standardised Rate Ratios (SRR) were calculated for each of these areas as an indication of how common ambulance callouts were when standardised according to residential population in each area. Estimates of relative social disadvantage for each area were obtained from 1996 ABS Census data. poisoning protocol was used and naloxone administered between July 1997 to June 1999. In the cases w here the age and gender data were recorded, 31% of cases were female, 89% were aged 15-44 years and 95% were between 15 and 54 years. These estimates are approximate because age was not recorded in 57.0% of cases and gender in 51.9% of cases. No relationship existed between these missing data and the area of the callout. Geographic distribution of ambulance calls to overdoses The two most common SLAs to which ambulances were called out to attend an overdose were South Sydney (n=1,819) and Liverpool (n=1,602), which together accounted for 37% of all calls (20.0% for South Sydney, 17.6% for Liver pool; see Table 1). Outside Sydney, the SLAs with higher rates were Newcastle with an average annual rate of 152 per 100,000, Orange with a rate of 126 and Kiama with a rate of 171 (see Table 1). The statistical subdivisions with the highest rates in Sydney were Inner Sydney (990) and Fairf ield Liver pool (631), with Newcastle-Hunter (111), Gosford (114), and Wollongong (149) recording the highest rates outside Sydney. Over the whole state, the correlation between social disadvantage and the ambulance attendance rate was r= –0.21, indicating that higher rates occurred in more disadvantaged areas. In Results There were 9,116 calls in which the ambulance drug overdose/ Table 1: Number of ambulance attendances 1997-99, population size, average rate per year rate per 100,000 population (all ages), and standardised rate ratios, by statistical local area (data for the 25 highest SLAs only). Statistical Local Area Sydney – inner South Sydney Botany Liverpool Sydney – remainder Marrickville Kiama Newcastle inner Orange Wollondilly Auburn Baranald Goulbur n Inverell Bathurst Leichhardt Penrith Greater Lithgow Manly Tweed Tamworth Strathfield Wollongong Fairfield Lismore Total (State) Number 1997-99 164 1819 519 1602 67 294 63 417 88 85 130 7 49 10 58 119 281 32 60 62 56 42 272 275 59 9,116 Population 3,732 79,460 35,938 124,292 10,114 79,876 18,374 137,265 34,828 34,583 53,266 2,934 21,490 4,622 29,146 60,749 167,868 19,994 37,703 39,148 35,580 27,170 183,497 189,108 43,551 6,295,368 Rate per year SRR 30.2 15.7 9.9 8.9 4.5 2.5 2.4 2.1 1.7 1.7 1.7 1.6 1.6 1.5 1.4 1.3 1.1 1.1 1.1 1.1 1.1 1.1 1.0 1.0 0.9 1.0 25.7 15.0 9.1 8.4 3.5 2.2 1.8 1.9 1.4 1.3 1.4 0.6 1.2 0.7 1.0 1.1 1.0 0.8 0.8 0.8 0.8 0.8 0.9 0.9 0.7 – 95% CI 35.2 16.5 10.8 9.3 5.8 2.8 3.0 2.3 2.1 2.1 2.0 3.4 2.1 2.7 1.8 1.6 1.3 1.6 1.4 1.4 1.4 1.4 1.1 1.1 1.2 – AUSTRALIAN AND NEW ZEALAND JOURNAL OF PUBLIC HEALTH VOL. 25 NO. 5 Vulnerable Groups Ambulance calls to suspected overdoses Sydney, the correlation was –0.46 but outside Sydney it was +0.21, indicating that there were higher rates of call outs in more advantaged (and perhaps more urbanised) areas. because data on amb ulance attendances was not available for the same period. Time of day of ambulance callouts Comparison of fatal heroin overdose and ambulance call rates Table 2 shows that the areas with the highest rates of ambulance attendances were those with highest rates of heroin overdose death. Inner Sydney recorded the highest rate per year of overdose deaths (37.0) and ambulance attendances (990.0), with Fairf ield-Liver pool recording the next highest rates (17.8 for fatal overdoses; 630.6 for ambulance attendances). Outside Sydney, Wollongong had the highest rate of heroin overdoses (7.7) and the highest ambulance attendance rate (148.6). The correlation between rates of fatal heroin overdose and ambulance attendances was r=+0.91. The relationship was stronger for Sydney areas (r=0.94) than for other areas in the state (r=0.48). The latter probably reflects the smaller number of deaths and hence greater variability in rates in areas with small populations; ambulance callout data may be less accurate as an indicator of opioid use outside major urban centres. These strong relationships were observed despite the fact that the heroin overdose data were recorded in 1992-96 rather than 1997-99 for ambulance attendances, The time of day at which ambulances were called to suspected overdoses was grouped in three-hour blocks; the distribution is displayed in Figure 1. The majority of calls (54%) were made between midday and 9pm. Calls were least likely to be made between midnight and 9am (19%). Discussion A large number of calls were made by the NSW Ambulance Service to suspected dr ug overdoses between July 1997 and June 1999: 4,300 in 1997-8, and almost 4,800 in 1998-9, with averages of 361 and 399 per month, respectively. This monthly average is higher than that estimated from a similar analysis of amb ulance calls in Victoria, where there was an average of 129 per month between November 1997 and January 1998 10 but differences in case ascertainment between the two data sources may limit comparisons. Greater consistency is needed between data in different States to permit comparisons. The data presented in the present paper are not approximates Table 2: Number of ambulance calls 1997-99, average rate per y ear among 15-44 year olds, and standardised rate ratios (SRR) by statistical subdivisions, and rate of fatal her oin overdose per year by statistical subdivision. Statistical Subdivision Number of callouts 1997-99 2,915 1,849 326 271 159 318 235 510 217 146 228 44 199 87 249 177 126 108 131 93 101 56 34 19 8,598 Rate per year Expected number 472 470 352 320 220 443 331 739 377 255 417 81 376 192 557 408 300 310 413 404 524 310 202 128 8,598 SRR 95% CI Fatal overdose average rate per year 1992-96 6.4 4.1 1.0 1.0 0.8 0.8 0.8 0.8 0.7 0.7 0.6 0.7 0.6 0.6 0.5 0.5 0.5 0.4 0.4 0.3 0.2 0.2 0.2 0.2 – 37.0 17.8 7.7 6.6 8.9 2.8 3.4 3.0 2.7 6.0 5.7 13.1 13.2 1.6 3.8 6.4 6.6 1.0 3.4 1.0 1.2 1.7 2.9 1.4 6.8 Inner Sydney Fairfield Liver pool Wollongong Outer South West Sydney Inner West Sydney Outer West Sydney Gosford Wyong Newcastle Hunter Mid West NSW Far Nor th Coast Canterbury Bankstown Southern Highlands Eastern Suburbs New England St George Sutherland Central West Sydney Northern Beaches Mid North Coast Lower Nor th Sydney Southern NSW Blacktown-Baulkham Hills Hornsby Kuringai South Coast Far West NSW Total (State) 6.0 3.8 0.8 0.8 0.6 0.6 0.6 0.6 0.5 0.5 0.5 0.4 0.5 0.4 0.4 0.4 0.4 0.3 0.3 0.2 0.2 0.1 0.1 0.1 – 2001 VOL. 25 NO . 5 AUSTRALIAN AND NEW ZEALAND JOURNAL OF PUBLIC HEALTH Degenhardt, Hall and Adelstein Article 20 18 16 14 12 10 8 6 4 2 0 12am - 3am6am- 9am- 12pm- 3p - 6p - 9p m m m 2:59am 5:59am 8:59am 11:59pm 2:59p 5:59p 8:59p 11:59am m m m Figure 1: Distribution of ambulance callouts by time of day. For all their limitations, the consistency of the ambulance data with other data on the characteristics of heroin users and the geographic and temporal distribution of fatal opioid overdoses is impressive. The agreement is all the more impressive given the smaller numbers of overdose deaths in some areas and the fact that the data covered two non-overlapping time periods. However, given the lower cor relation between fatal heroin overdoses and ambulance callouts in small non-urban areas, other indicator data may be better indicators of trends in these areas. These findings suggest that data on rates of ambulance attendance at suspected opioid overdoses constitute an additional promising indicator for monitoring trends in non-fatal opioid overdoses and indirectly, of opioid use. for the total number of non-fatal overdoses that occurred in NSW in the period (since only around half of non-fatal overdoses will involve an ambulance being called4), b ut they cer tainly allow observation of trends over time in the numbers of persons who were attended. This permits us to examine time trends in this proxy measure. While public health campaigns (such as those to increase calls to ambulances in cases of suspected overdose) may affect the likelihood of calling an ambulance, heroin use had a high profile over the whole period in which this data was collected and effor ts to increase ambulance call outs to suspected over doses began in 1997. The main trends were clear and consistent with other data. First, when gender was recorded it was female in a third of cases. This is higher than the 20% of females among opioid overdose deaths 11 but similar to the proportion of females in the methadone maintenance treatment (MMT)12,13 in IDU samples 14 and among needle and syringe programs attendees (NSP).15 Persons who have over dosed and been attended by ambulances may be more representative of the opioid using population than overdose fatalities. Second, most ambulance attendances and fatal opioid overdose deaths7,8 occur among persons aged 15-44 years, and most often in those aged 25-34 years. Although these patterns are consistent with what is known about the characteristics of heroin users, we do not know the age and gender of about half of the sample. Third, the majority of ambulance callouts occurred in Sydney and other large cities. The two SLAs with the highest rates were Liverpool and South Sydney, the areas in which the largest NSW heroin markets are concentrated.16 Fatal heroin overdose deaths and ambulance callouts were concentrated in the same geographic areas, par ticularly in Sydney; this clustering indicates where use occurred rather than where persons resided. Fourth, the time of day of callouts is similar to that for heroin fatalities in NSW.17,18 In South Western Sydney between 1992 and 1996, 37% of deaths were estimated to occur between midday and 6pm18 and 37% of ambulance calls were made within this period. This pattern is similar to that in ambulance callouts in Victoria,10 the ACT19 and Germany.20 percentage

Journal

Australian and New Zealand Journal of Public Health – Wiley

Published: Oct 1, 2001

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