While the individual-level efficacy of opioid agonist therapy (OAT) on reducing mortality has been established and quantified in meta-analyses, demonstrating its effect at population-level has been more challenging. Such evidence is key to support and inform scale up of OAT programs globally, which is urgently needed as most programs reach only a small proportion of those in need. No studies have estimated the impact of a large-scale OAT program on mortality through reproducing mortality dynamics among OAT recipients over time. We used linked government OAT program, incarceration and mortality data from the Australian State of New South Wales (NSW) from 2001-2018 to develop and inform a dynamic mathematical model of overdose and other cause mortality. This reproduces the treatment and incarceration trajectories of nearly 50,000 people receiving OAT at least once over this period, as well as mortality patterns by cause of death, OAT status and incarceration stage.
Over 2001-2020, we estimate OAT provision reduced overdose and other cause mortality among the cohort by 53% and 27%, respectively. Over 33,000 life years were gained, corresponding to nearly 10 life years gained per 100 person-years on OAT. The prison OAT program and post-release OAT-linkage contributed to 12% of overall OAT program impact, mostly averting deaths in the month post-release. Indeed, such programs prevent treatment discontinuation and high mortality upon prison release. Our study shows that the OAT program in NSW has had a major impact on reducing opioid overdose deaths and total deaths among people engaged with treatment in the past 20 years. This can be attributed to both the high coverage of OAT over time (>50%) and the relatively long average duration of OAT episodes (1.74 years) among this cohort, emphasizing the key importance of retention for OAT program implementation
Background and Aims:
The individual-level effectiveness of opioid agonist treatment (OAT) in reducing mortality is well established but there is less evidence on population-level benefits. We use modeling informed with linked data from the OAT program in New South Wales (NSW), Australia, to estimate OAT provision impact on population mortality.
We used linked data on OAT provision, incarceration, and mortality among a cohort of 49,359 individuals who ever received OAT in NSW from 2001-2018 to inform a dynamic model of overdose and other cause mortality. The model incorporated elevated mortality post-release from prison, and OAT impact on reducing mortality and incarceration. We estimated impact of OAT provision in community and prison on mortality among the OAT cohort from 2001-2020. We also assessed impact of eliminating excess mortality during OAT initiation/discontinuation.
Among the cohort, mortality was 0.9 per 100 person-years, OAT coverage and retention remained high (>50%, 1.74 years/episode). Over 2001-2020, we estimate OAT provision reduced overdose and other cause mortality among the cohort by 53% [95% credible interval: 49%-56%] and 27% [22%-30%], respectively. We estimate 1.2 deaths averted and 9.7 life-years gained per 100 person-years on OAT. Prison OAT with post-release OAT-linkage accounted for 12% [11%-13%] of all deaths averted by the OAT program, primarily through preventing deaths in the first month post-release. Preventing elevated mortality during OAT initiation and discontinuation could have averted up to 1.4% [1%-2%] and 3% [2%-5%] of deaths, respectively.
The community and prison OAT program in NSW substantially reduced population-level overdose and all-cause mortality in the past 20 years, partially due to high retention which should be a key consideration of national programs.