Supervised Injection Facility Utilization Patterns: A Prospective Cohort Study in Vancouver, Canada

Abstract

Although the health and community benefits of supervised injection facilities are well documented, little is known about long-term patterns of utilization of this form of health service. The present study seeks to longitudinally characterize discontinuation of use of a supervised injection facility in Vancouver, Canada. Data were drawn from 2 community-recruited prospective cohorts of people who inject drugs between December 2005 and December 2016. In 2018, extended Cox regression for recurrent events was used to examine factors associated with time to cessation of supervised injection facility use during periods of active injection. Of 1,336 people who inject drugs that were followed for a median of 50 months, 847 (63.4%) participants reported 1,663 6-month periods of supervised injection facility use cessation while actively injecting drugs (incidence density of 26.6 events per 100 person-years). An additional 2,282 (57.8%) of the total 3,945 6-month periods of supervised injection facility use cessation occurred during periods of injection cessation. In multivariable analyses, enrollment in methadone maintenance therapy (adjusted hazard ratio=1.41) and HIV seropositivity (adjusted hazard ratio=1.23) were positively associated with supervised injection facility use cessation during periods of active injection, whereas homelessness (adjusted hazard ratio=0.59), at least daily heroin injection (adjusted hazard ratio=0.70), binge injection (adjusted hazard ratio=0.68), public injection (adjusted hazard ratio=0.67), nonfatal overdose (adjusted hazard ratio=0.73), difficulty accessing addiction treatment (adjusted hazard ratio=0.69), and incarceration (adjusted hazard ratio=0.70) were inversely associated with this outcome (all p<0.05). The most commonly reported reasons for supervised injection facility use cessation were injection drug use cessation (42.3%) and a preference for injecting at home (30.7%). These findings suggest that this supervised injection facility successfully retains people who inject drugs at elevated risk of drug-related harms and indicate that many supervised injection facility clients neither use this service nor inject drugs perpetually.