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Ambulance calls to suspected drug overdoses: Analysis of New South Wales patterns - July 1997 to June 1999

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Author: Louisa Degenhardt, Wayne Hall, Barbara-Ann Adelstein

Resource Type: Technical Reports

NDARC Technical Report No. 94 (2000)


There has been a substantial increase in the number and rate of opioid overdose deaths in Australia over the past three decades. Non-fatal opioid overdoses are even more common among heroin users. Non-fatal overdoses are instances in which a person loses consciousness, breathing is depressed, but death does not occur. Evidence suggests that perhaps half of these overdoses may result in an ambulance being called. Overdoses attended by ambulance officers may therefore provide an important source of information about trends in heroin use in NSW and other states.

The aims of the current report were: 1) to examine the number of ambulance call-outs over the period; 2) to explore of the quality of the data on these calls; 3) to examine the temporal and geographic trends in heroin use; and 4) to compare data on ambulance attendances with data on fatal heroin overdose deaths in NSW. The current report examined data on New South Wales ambulance calls over a two-year period, July 1997 to June 1999.

Data were provided by the NSW Ambulance Service on the occasions when an ambulance attended a person with whom the poisonings protocol was used, and to whom naloxone was administered. Age and gender were coded for some cases, and the postcode of the area to which the ambulance was called was recorded. Analyses of the geographic distribution of ambulance attendances were carried out using approximates of the Australian Bureau of Statistics (ABS) Statistical Local Area (SLA) Statistical Subdivision (SSD). Estimates of social disadvantage for each area were correlated with the rate of ambulance attendances for each region. The number of callouts per month was plotted, and the distribution of callouts by time of day and day of week was calculated.

A total of 10,324 callouts were made during the study period. The majority of cases in which age was recorded were in the age range of 15-44 years (89%), and almost all cases (95%) were in the age range 15-54 years. Around one third (31%) of cases for whom gender was recorded were female. This suggests that overdoses attended by ambulances may be more representative of the gender distribution in the heroin using population than are overdose fatalities. Unfortunately, age or gender was not recorded for around half of cases, so caution must be taken in interpreting these figures.

The two most common SLAs to which ambulances were called out to attend an overdose were South Sydney (n = 2,034) and Liverpool (n = 1,794). Outside Sydney, the areas with higher callout rates tended to be the larger towns – Newcastle, Orange, and Kiama. The SSDs of Inner Sydney (1114) and Fairfield-Liverpool (708) had the highest average annual rates per 100,000 population aged 15-44 years, with Newcastle-Hunter, Gosford and Wollongong recording the highest rates outside Sydney. In Sydney, higher rates of callouts occurred in areas of greater disadvantage, while areas outside Sydney with higher callout rates had greater social advantage. Comparison with the geographic distribution of fatal and non-fatal overdoses revealed a strong correlation between the two data sources on overdose.

In the 1997-1998 period, there were a total of 4,335 recorded ambulance attendances in which the poisonings protocol was used and naloxone was administered, compared to 5,989 in 1998-1999. This was an average of 361 calls per month in 1997-1998, and a monthly average of 499 in 1998-1999. Over half of calls (54%) were made between 12pm and 9pm.

These findings suggest data on rates of ambulance attendance at suspected overdose cases are a promising indicator for monitoring trends in heroin use and in non-fatal overdoses. In the future, this could allow identification of problematic areas, as well as give an indication of areas in which heroin use becomes a more widespread problem. Data over a larger time period would also allow more formal analysis of time-related trends.