Abstract
Illicit heroin use is a worldwide problem, with significant health and social costs. Treatment is known to be effective in changing heroin use habits, but it often needs to be provided over a lifetime, with people cycling in and out of treatment. It is therefore important to capture a long-term perspective on heroin use careers. The aim of this project was to build a lifetime microsimulation model of heroin using careers. This paper describes the conceptual logic of the model, the input parameters and the verification and validation results. A microsimulation model was chosen as the most appropriate simulation platform with 9 states, and 111,400 individuals (aged between 18 and 60) each with gender, HIV (human immunodeficiency virus) and HCV (hepatitis C) status, and treatment history. Probabilities associated with crime commission and individually calculated lengths of stay in each state were determined from multiple datasets. The model included costs associated with treatment provision, healthcare services, criminal activity, life years lost, and family benefit of treatment. The final model represented 42 years of a heroin use career for a cohort based on Australian (New South Wales) data. Individuals cycle into and out of heroin using states (including abstinence), as well as treatment and prison states. We were able to build a stable, tractable model and verified all parameters. Validation against external data sources revealed high validity. While there are limitations associated with any model, the heroin career model now has the potential to be used for simulations of alternate policy scenarios.
Highlights
Heroin is an illegal drug that is widely abused
The microsimulation model (MSM) model for heroin use careers takes the population of individuals who have ever used heroin for one Australian state (NSW) including those who used heroin previously and are currently abstinent, those in treatment subgroups as well as those in prison
We found three adjustments that met these criteria: the transition from S3 into S6 is adjusted by age; the transition into any treatment state is adjusted by gender; and longer length of stay (LOS) in S5 and S6 increases the probability of transition to S1 compared to S3
Summary
Heroin is an illegal drug that is widely abused. It is estimated that there are around 16.5 million heroin users worldwide (a 0.4% population prevalence rate). The aim of this paper is to detail the development of a microsimulation model (MSM) for heroin use which can be used to assess the net social benefit of current heroin treatment strategies, such that the final model can be used to compare different combinations of treatment alternatives through modelled scenarios This will lead to better informed policy decisions about the mix and type of treatments. The second model, by Zarkin et al (2005) models the costs and benefits of methadone treatment related to heroin use, criminal activity, labour market participation and health care utilization This model follows 1,000,000 individuals from 18 to 60 year olds who are representative of the United States population. The paper concludes with a discussion of both the strengths and limitations of the approach taken here as well as considering the future applications of the model
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