Opioid substitution therapy as a strategy to reduce deaths in prison : retrospective cohort study

Objectives: To describe deaths in prison among opioid-dependent people, and examine associations between receipt of opioid substitution therapy (OST) and risk of death in prison. Design: Retrospective cohort study. Setting: Adult prisons in New South Wales (NSW), Australia. Participants: 16 715 opioid-dependent people who were received to prison between 2000 and 2012. Interventions: Opioid substitution therapy. Primary outcome measures: Natural and unnatural (suicide, drug-induced, violent and other injury) deaths in prison. Results: Cohort members were in prison for 30 998 person-years (PY), during which time there were 51 deaths. The all-cause crude mortality rate (CMR) in prison was 1.6/1000 PY (95% CI 1.2 to 2.2/1000 PY), and the unnatural death CMR was 1.1/1000 PY (95% CI 0.8 to 1.6/1000 PY). Compared to time out of OST, the hazard of all-cause death was 74% lower while in OST (adjusted HR (AHR): 0.26; 95% CI 0.13 to 0.50), and the hazard of unnatural death was 87% lower while in OST (AHR: 0.13; 95% CI 0.05 to 0.35). The all-cause and unnatural death CMRs during the first 4 weeks of incarceration were 6.6/1000 PY (95% CI 3.8 to 10.6/1000 PY) and 5.5/1000 PY (95% CI 2.9 to 9.4/1000 PY), respectively. Compared to periods not in OST, the hazard of all-cause death during the first 4 weeks of incarceration was 94% lower while in OST (AHR: 0.06; 95% CI 0.01 to 0.48), and the hazard of unnatural death was 93% lower while in OST (AHR: 0.07; 95% CI 0.01 to 0.53). Conclusions: Mortality of opioid-dependent prisoners was significantly lower while in receipt of OST.