Trends in engagement in the cascade of care for opioid use disorder, Vancouver, Canada, 2006-2016

Background: A cascade of care framework has been proposed to identify and address implementation gaps in addiction medicine. Using this framework, we characterized temporal trends in engagement in care for opioid use disorder (OUD) in Vancouver, Canada. Methods: Using data from two cohorts of people who use drugs, we assessed the yearly proportion of daily opioid users achieving four sequential stages of the OUD cascade of care [linkage to addiction care; linkage to opioid agonist treatment (OAT); retention in OAT; and stability] between 2006 and 2016. We evaluated temporal trends of cascade indicators, adjusting for socio-demographic characteristics, HIV/HCV status, substance use patterns, and social-structural exposures. Results: We included 1615 daily opioid users. Between 2006 and 2016, we observed improvements in linkage to care (from 73.2% to 78.9%, p = < 0.001), linkage to (from 69.2% to 70.6%, p = 0.011) and retention in OAT (from 29.1% to 35.5%, p = < 0.001), and stability (from 10.4% to 17.1%, p = < 0.001). In adjusted analyses, later calendar year of observation was associated with increased odds of linkage to care (Adjusted Odds Ratio [AOR] = 1.02, 95% Confidence Interval [CI]: 1.01-1.04), retention in OAT (AOR 1.02, 95% CI: 1.01-1.04) and stability (AOR = 1.03, 95% CI: 1.01-1.05), but not with linkage to OAT (AOR 1.00, 95% CI: 0.98-1.01). Conclusions: Temporal improvements in OUD cascade of care indicators were observed. However, only a third of participants were retained in OAT in 2016. These findings suggest the need for novel approaches to improve engagement in care for OUD to address the escalating opioid-related overdose crisis.