Mortality among first-time opioid agonist therapy patients in Austria, 2002-2021: A national retrospective cohort study

Background

There is a substantial evidence base from large observational studies that opioid agonist therapy (OAT) reduces mortality risk, in particular for drug-related overdose deaths and other injuries. Slow-release oral morphine (SROM) is the most prescribed OAT medication in Austria. To date, no well powered studies have been conducted to directly compare mortality risk in an OAT patient population predominantly utilizing SROM (57% of all OAT patients). We aim to investigate potential variations in the risk of all-cause mortality and drug-related overdose mortality among first-time OAT patients in Austria at treatment initiation, during treatment, and following treatment cessation, and compare these outcomes based on OAT medication.

Methods

We will conduct a register-based retrospective cohort study using linked data encompassing all patients in Austria who initiated their first OAT episode between January 1, 2002, to December 31, 2021 (n=26,031). We will compare crude mortality rates (CMRs) for both all-cause and drug-related overdose mortality. Standard regression techniques will be employed to model the risk for mortality during treatment and periods outside of treatment, stratified by OAT medication type.

Results

Our preliminary research findings encompass 26,031 individuals contributing a total of 279,030 person-years (PY) of observation. Of these years, 128,393 (46%) were observed during the first treatment episode. 76% were male, 63% were younger than 30 years at beginning of follow-up (median age 26, IQR 22-33). Thirty-three percent of all first-time patients initiated treatment with buprenorphine, 28%with SROM, and 21% with methadone. The median time in the first OAT episode was 2.44 years (IQR 0.4–8.7). Over the 19 years observation period, there were 2,358 all-cause deaths, of which 804 were drug-related overdose deaths according to the EMCDDA definition.

Conclusions

Drug-related overdose deaths are increasing in many countries, most notably in the United States, Canada, the UK, and other parts of Europe. As countries strive to address the impact of opioid use disorders, our findings will hold direct clinical relevance, particularly for those offering or contemplating the introduction of SROM as an additional medication option in OAT.