Are gaps in rates of retention on buprenorphine for treatment of opioid use disorder closing among veterans across different races and ethnicities? A retrospective cohort study.

Introduction: The U.S. Veterans Health Administration has undertaken several initiatives to improve veterans' access to and retention on buprenorphine because it prevents overdose and reduces drug-related morbidity. We aimed to determine whether improvements in retention duration over time was equitable across veterans of different races and ethnicities.

Methods: This retrospective cohort study was conducted among veterans who initiated buprenorphine from federal fiscal years (FY) 2006 to 2020 after diagnosis of opioid use disorder. Using an accelerated failure time model, we estimated the association between time to buprenorphine discontinuation and FY of initiation, race and ethnicity, and other control covariates. We followed veterans from buprenorphine initiation until they discontinued or had a censoring event. We then estimated the predicted median days retained on buprenorphine, the average marginal effect of initiating in a later FY, the same measure by race and ethnicity, the incremental effect of the various racial and ethnic identities in contrast to non-Hispanic White, and the total change in the size of the gap over the 15 years of the study between veterans with a minoritized racial or ethnic identity compared to non-Hispanic White veterans.

Results: Most of the 31,797 veterans in the sample were non-Hispanic White (74.5 %), from urban areas (83.5 %), male (92.0 %), and had significant comorbidities, most frequently anxiety disorders (51.0 %) and depression (63.0 %). Overall, 49.8 % of veterans were retained at least 180 days. The average marginal effect of FY was 7.0 days [95%CI:5.3, 8.8] but was significantly smaller among veterans identifying as Black or African American [3.2 days; 95%CI:2.4, 4.1] or Asian [3.6 days; 95%CI:1.6, 5.7] compared to veterans who identify as non-Hispanic White [7.9 days; 95%CI:5.9, 9.9]. Additional measures of change were significant for veterans identifying as Hispanic White or with two or more races.

Conclusion: Although buprenorphine retention in OUD treatment improved for all veterans over the 15-year study period, veterans from most minoritized racial and ethnic groups fell further behind as gains in duration on therapy accrued primarily to non-Hispanic White veterans. Targeted interventions addressing specific challenges experienced by veterans with minoritized identities are needed to close gaps in retention on buprenorphine.