NDARC Technical Report No. 198 (2004)
Problems related to heroin use, such as dependence, blood borne virus transmission, premature death from overdose and crime, negatively affect the community in ways that are disproportionate to the relatively small proportion of Australian adults who are dependent on heroin. An important question to ask (and answer) is therefore: how many people use heroin? Such an exercise was undertaken in 2000, when Hall and colleagues estimated the population prevalence of opioid dependence using 1997/1998 data.
In recent years, however, we have seen significant changes in the heroin market in Australia. Early in 2001, anecdotal reports were received of a sharp reduction in the availability of heroin. These reports were initially confirmed by research in convenience samples (Day et al., 2003; Weatherburn, Jones, Freeman, & Makkai, 2001), and later confirmed in the monitoring systems that had documented the increasing heroin availability during the previous five years (Darke, Topp, Kaye, & Hall, 2002; Topp et al., 2002). A common issue for consideration has been the extent to which changes in the availability of heroin may have impacted upon the number of persons using the drug. This report seeks to examine which methods for estimating the number of heroin users are most appropriate to use when the numbers of heroin users may be rapidly changing in response to marked changes in availability of their drug of choice.
Achieving this aim is not simple. Making estimates of a hidden population, such as heroin users, is difficult for a range of reasons in the best of circumstances. Added to these difficulties are complications introduced by marked changes in drug supply.
Given the illegal and stigmatised nature of heroin use, it is not a simple task to estimate the number of dependent heroin users in Australia. There are no widely accepted "gold standard" methods for estimating the size of this "hidden population". The favoured strategy is to apply a variety of different estimation methods of varying validity to different data sources, looking for convergence in the estimates. We carried out an evaluation of data sources used to produce estimates of the number of heroin users, and of methods that might be able to measure the size of this population during relatively short periods (i.e. annually).
The aims of the current study were to:
The evaluation of methods used is contained in Degenhardt et al (2004).
Estimates were generated from secondary analyses of existing databases. We made estimates of the number of current regular heroin users. The number of opioid dependent persons in total is likely to include the number of persons maintained upon opioid pharmacotherapy as well as our estimates of the number of regular heroin users. The data sources that were used in the current study included:
Clear increases in the scale of harms related to heroin use were documented in the latter half of the 1990s, with sharp reductions from 2001. These changes were relatively consistent across the data sources examined, with the exception of the total number of persons in opioid pharmacotherapy, which has steadily increased over time as new heroin dependent persons have entered treatment, and others have remained stabilised on it.
There has been a significant drop in the estimated number of current, regular heroin users in NSW. This drop was sustained in 2002. Detailed estimates of the number in NSW and in Australia, as well as stratification by age and gender, are provided in the companion report (Degenhardt et al., 2004).
The changes we estimate to have occurred were driven by reductions in heroin supply. They were not driven by changes in demand for heroin – injecting drug users and key informants from drug monitoring systems and studies conducted since the heroin shortage have both confirmed that users wanted heroin but were finding it difficult to obtain (Breen et al., 2003; Day et al., 2003). It seems reasonable to assume that when the availability of heroin increases again, the number of persons engaging in regular heroin use is likely to increase. Thus, although the heroin shortage has reduced the harms related to heroin use, we should not expect these lower levels of harm to be maintained if or when supply returns and heroin use increases.
Despite the difficulties in estimating numbers of users following an abrupt onset of a heroin shortage, the multiple methods used suggested that there has been a reduction in regular heroin use in the community. Some of these users probably moved to using other drugs, but if they did, it did not appear to be to a degree that fully offset the reduction in the number of regular heroin users. It remains to be seen how many of the heroin users who have entered opioid maintenance and other treatment return to heroin use if or when heroin supply improves again.
Citation: Degenhardt, L., Rendle, V., Hall, W., Gilmour, S. and Law, M. (2004) Estimating the number of current regular heroin users in NSW and Australia 1997-2002, Sydney: National Drug and Alcohol Research Centre.