Hospitalisations for non-fatal overdose among people with a history of opioid dependence in New South Wales, Australia, 2001–2018: Findings from the OATS retrospective cohort study

Background: To examine, among a cohort of opioid dependent people with a history of opioid agonist treatment (OAT), the frequency and incidence rates of non-fatal overdose (NFOD) hospital separations over time, by age and sex. Methods: Retrospective cohort study of people with a history of OAT using state-wide linked New South Wales (NSW) data. The incidence of NFOD hospital separations involving an opioid, sedative, stimulant or alcohol was defined according to the singular or combination of poisoning/toxic effect using ICD-10-AM codes. Crude incidence rates were calculated by gender, age group and calendar year. Results: There were 31.8 (31.3–32.3) NFOD per 1,000 person-years (PY). Opioid NFOD incidence was higher in women than men: incidence rate ratio (IRR) 1.11 per 1,000PY; 95 %CI: [1.06–1.17]; women had higher sedative NFOD rates than men, IRR 1.27 per 1,000PY [1.21–1.34]. Participants ≤25 years, 26-30yrs, and 31-35yrs had higher incidence of opioid NFOD compared to 46+yrs, with IRRs of: 1.45 per 1,000PY; [1.32–1.59]; 1.20 per 1,000PY; [1.11–1.30] and 1.22 per 1,000PY; [1.13–1.32], respectively. Between 2006-7 and 2016-17, the cohort accounted for 19 % of NSW opioid NFOD episodes, 12 % of sedative, 14 % of stimulant and 5 % of acute alcohol-related NFOD. Conclusions: Hospital stays due to NFOD are a relatively frequent occurrence among opioid-dependent people. There are clear differences in rates and substances involved by sex, age and over time. Evidence-based interventions that prevent overdose among people who are opioid dependent need to be delivered to scale, including widespread community provision of naloxone.