Methods: Retrospective cohort study of 10,744 new OAT entrants between 2004-2010 in New South Wales, Australia, linked to data on charges, incarceration and mortality to the end of 2011. Time-dependent OAT exposure was modelled using Cox proportional hazards models (time to first charge) and Anderson-Gill intensity models (total charge-days). Retention in OAT was modelled using two features of treatment engagement - number of OAT episodes and proportion of follow-up in OAT (presented in quartile groupings: lowest, low-mid, low-high, highest) using zero-inflated negative binomial regression (total charges). All models were adjusted for sociodemographic, criminographic and treatment-related variables.
Findings: Overall, 5,751 (53.5%) people were charged with an offence. In adjusted analyses, OAT was associated with an initial benefit in delaying the time to first charge (Hazard Ratio (HR) 0.43, 95% Confidence Interval (CI) 0.33-0.55) and reducing total charge-days (HR 0.39, 95% CI 0.30-0.52), however, these protective effects decayed over time. Total charge rates were higher as the number of OAT episodes increased (Incident Rate Ratio (IRR) 1.13, 95% CI 1.11-1.15), and where relatively lower proportions of time were spent in OAT [IRR among lowest three quartiles ranged from 1.11 (95% CI 1.02-1.21) to 1.22 (95% CI 1.121-1.33)].
Interpretation: OAT is associated with a significant reduction in overall charge rates and is more protective as treatment engagement increases. Maximising treatment retention is critical to achieving long-term health and social benefits of OAT.
- Opioid substitution treatment
- opiod-related disorders
- data linkage
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- Bristol Medical School (PHS) - Professor in Public Health and Epidemiology
- Bristol Medical School - Interim Head of School
- Bristol Population Health Science Institute
- Health Protection Research Unit (HPRU)
- Centre for Academic Mental Health
- Infection and Immunity
- Centre for Academic Primary Care
Person: Academic , Member, Group lead, Professional and Administrative