Trends in opiate overdose deaths in Australia 1979-1995

To determine if there had been an increase in the rate of opioid overdose deaths between 1979 and 1995, and to describe the characteristics of persons who died of an opioid overdose.

Opioid overdose deaths were defined according to ICD-9 as deaths due to drug dependence (codes 304.0 and 304.7) and accidental opiate poisoning (code E850.0). Data were obtained from a national register of deaths compiled by the Australian Bureau of Statistics on: age at death, sex and jurisdiction of all such deaths between 1979 and 1995 inclusive. Mortality rates were calculated for each sex for the 15-24, 25-34 and 35-44 age groups.

The number of opioid overdose deaths rose from 70 in 1979 to 550 in 1995. The rate (per million of the population aged 15-44) increased from 10.7 to 67.0. The increase was more marked among males than females, increasing 6.8 times among males (from 15.3 in 1979 to 104.6 in 1995) and 4.7 times among females (from 5.9 in 1979 to 27.9 in 1995). New South Wales consistently accounted for around a half of all male overdose fatalities and its overdose mortality rate was almost twice that in Victoria, and three times that in the remaining states. The average age at death for males increased from 24.5 years in 1979 to 30.6 years in 1995. The increase in overdose mortality was greatest among men and women aged 35 to 44 years, and 25 and 34 years. An analysis by birth cohort showed that 46% of male overdose deaths and 50% of female overdose deaths in the period occurred among those born between 1960 and 1969. Deaths among persons born between 1950 and 1959 accounted for 38% of male and 33% of female deaths.

There has been a statistically significant increase in opioid overdose mortality between 1979 and 1995, most of it occurring among persons who initiated heroin use in the late 1970s and early 1980s. Recent initiations of heroin use among those born between 1970 and 1979 have begun to be reflected in an increased rate of opioid overdose deaths. If their mortality experience replicates that of earlier birth cohorts then opioid overdose mortality will continue to increase.