Back-projection estimates of the number of dependent heroin users in Australia

To plan an appropriate response to heroin use in Australia, good estimates are needed of the numbers of dependent heroin users, the group who are most in need of treatment, most at risk of fatal opioid overdose and most at risk of contracting and transmitting blood-borne viruses.

Back-projection methods were used to estimate the numbers of people starting dependent heroin injecting in Australia between 1960 and 1997. Separate analyses were based on national opioid overdose deaths and numbers of new entrants to methadone treatment in New South Wales (NSW). Estimates of the rates at which dependent heroin users cease heroin use, commence methadone treatment or die from opioid overdoses were estimated from external data sources.

Back-projection estimates derived from opioid overdose deaths indicated that there were 104 000 (lower limit of 72 000 and upper limit of 157 000) people who were heroin dependent in Australia between 1960 and 1997. Of these it was estimated that 67 000 (39 000-120 000) were still heroin dependent at the end of 1997. Back-projection estimates based on numbers of new entrants to methadone treatment in NSW indicated that there were 108 000 (82 000-141 000) heroin-dependent people in Australia between 1960 and 1997, of whom 71 000 (47 000-109 000) were estimated to be heroin dependent at the end of 1997. Both analyses indicated that the number of heroin-dependent people in Australia has increased substantially from the early 1970s onwards.

Back-projection estimates based on analyses of treatment entries and opioid overdose deaths provide an additional method for estimating the numbers of heroin-dependent people in the population. The addition of these methods to existing methods, using different data sources and statistical methods, should improve consensus estimates of the numbers of heroin-dependent people.