Trajectories of Retention in Opioid Agonist Therapy in a Canadian Setting

Background: Long-term engagement in opioid agonist therapy (OAT) has been consistently associated with reduced risk for morbidity and mortality in people with opioid use disorder (OUD). However, the dynamic nature of engagement/disengagement in OUD care for over time is poorly captured by traditional metrics. We characterized long-term longitudinal trajectories of engagement in OAT in Vancouver, Canada, between 2005 and 2018.Methods: Data were derived from two community-recruited prospective cohorts of people who use drugs. Retention in OAT was defined as self-reported enrolment in OAT for two consecutive follow-up periods (an approximately six-month retention interval). We used latent class growth analysis to identify OAT engagement trajectories during the first five years after OAT initiation and multivariable logistic regression to evaluate predictors of trajectory group membership.Results: We identified four OAT retention trajectories among 438 OAT initiators: “consistently high” (36%), “consistently low” (23%), “increasing” (23%), and “decreasing” (15%). Employment was a significant cross-cutting predictor of membership of all sub-optimal OAT engagement patterns compared to consistently high trajectories. We also found that initiating OAT after 2014 (when regulatory changes to the provincial OAT program were introduced) was associated with the “consistently low” engagement group relative to others.Conclusions: We identified four distinct OAT engagement trajectories in Vancouver, Canada, with employment being a common predictor of sub-optimal care trajectories, suggesting the need to explore alternative OAT models to address employment-related barriers. Care trajectory analysis could help inform tailored interventions to specific populations of people with OUD at specific time points to improve engagement in OAT, and decrease opioid-related morbidity and mortality.