Opioid agonist therapy and mortality among First Nations and other residents with concurrent alcohol use disorder in British Columbia, Canada: A population-based cohort study

Background: Despite the prevalence of alcohol use among people with opioid use disorder (PWOUD) engaged in opioid agonist therapy (OAT), clinical care guidance for concurrent alcohol use disorder (AUD) and OUD is scarce. We assessed the prevalence and risk of mortality for concurrent AUD among PWOUD who accessed OAT in British Columbia (BC).

Methods: Data were obtained from six linked population-level health administrative datasets to identify PWOUD from January 1996 to March 2020. All-cause age and sex standardized mortality ratios (SMR) were calculated to determine the mortality risk by OAT status (on vs. discontinued), stratified by First Nations and other residents with concurrent AUD and OUD. Adjusted risk ratios compared the relative risk of mortality by AUD status (AUD detected vs. not) among First Nations and other residents.

Results: We identified 62,110 PWOUD who received OAT, including 6305 (10.2%) First Nations. OAT substantially lowered the SMR among First Nations (SMR=6.6, 95% CI: 5.4-8.1) and other residents (SMR=6.6; 95% CI: 6.2-7.0) with concurrent AUD and OUD, compared to those who discontinued (SMR=22.7, 95% CI: 20.4-25.1, SMR=17.5, 95% CI: 16.8-18.2 respectively). The risk of mortality was 1.9 (95% CI: 1.6-2.2) times higher for First Nations and 2.0 (95% CI: 1.8-2.2) times higher for other residents with concurrent OUD and AUD compared to those without an indication of AUD.

Conclusions: The protective effect of OAT remained despite the presence of a concurrent AUD among both First Nations and other residents with OUD. Findings have implications for clinical care management of concurrent disorders.