Evaluating the population-level effects of overdose prevention sites and supervised consumption sites in British Columbia, Canada: Controlled interrupted time series

Abstract

Background On 14 April 2016, British Columbia’s Provincial Medical Health Officer declared the overdose crisis a public health emergency, sanctioning the implementation of new overdose prevention sites (OPS) and supervised consumption sites (SCS) across the province. Methods We used the BC Centre for Disease Control’s Provincial Overdose Cohort of all overdose events between 1 January 2015 and 31 December 2017 to evaluate the population-level effects of OPSs and SCSs on acute health service use and mortality. We matched local health areas (LHA) that implemented any site with propensity score matched controls and conducted controlled interrupted time series analysis. Results During the study period, twenty-five OPSs and SCSs opened across fourteen of British Columbia’s 89 LHAs. Results from analysis of LHAs with matched controls (i.e. excluding Vancouver DTES) were mixed. Significant declines in reported overdose events, paramedic attendance, and emergency department visits were observed. However, there were no changes to trends in monthly hospitalization or mortality rates. Extensive sensitivity analyses found these results persisted. Conclusions We found OPSs and SCSs reduce opioid-related paramedic attendance and emergency department visit rates but no evidence that they reduce local hospitalization or mortality rates.

Using synthetic controls to estimate the population-level effects of Ontario’s recently implemented overdose prevention sites and consumption and treatment services

“…Our results also agree with simpler analysis we conducted to evaluate British Columbia’s recently implemented OPSs (Panagiotoglou, 2022). In both studies, we used controlled interrupted time series and reported aggregate, population-level results.…”

“…Our province-wide analysis found positive effects of SCSs on opioid-related ED visits and hospitalizations, but no statistically significant effect on opioid-related mortalities. These results agree with our province-wide findings on the effects of OPSs in British Columbia, while demonstrating beneficial impacts on hospitalizations not observed when we analyzed the BC Centre for Disease Control’s Overdose Cohort (Panagiotoglou, 2022). The Ontario results also align with findings from a mathematical model estimating the synergistic effects of BC’s harm reduction interventions (Irvine et al, 2019).…”

“…Past studies demonstrated Vancouver’s supervised injection facility, first implemented in 2003, significantly reduced local overdose mortality rates (Marshall BDL, Milloy MJ, Wood E, Montaner JS, & Kerr T, 2011). More recent studies evaluating other SCSs have found consistently positive effects on overdose- related ED visit and paramedic attendance rates, but no evidence of effect on mortality or hospitalization rates (NCHECR, 2007; Panagiotoglou, 2022; The Evaluation of Overdose Prevention Sites Working Group & Lori Wagar, 2018). By comparing outcome rates between PHUs that implemented any SCS with comparable synthetic PHUs not exposed to the intervention, controlling for concomitant time-varying interventions (i.e.…”

“…Our aim is to estimate the population-level effects of Ontario's SCSs implemented between 2017 and 2020 (inclusive) on opioid-related ED visit, hospitalization, and mortality rates, while controlling for other time-varying interventions including residents treated with prescription opioids, residents receiving OAT, and number of pharmacy and community naloxone kits distributed, all per 100,000 population. We hypothesize that SCSs had no level and modest trend effects on health service use and mortality rates based on results from a similar analysis we conducted using the British Columbia Centre for Disease Control's Overdose Cohort data (Panagiotoglou, 2022).…”

“…Our aim is to estimate the population-level effects of Ontario’s OPS/CTSs implemented between 2017 and 2020 (inclusive) on opioid-related ED visit, hospitalization, and death rates, while controlling for other time-varying interventions including rates of prescription opioids for pain management and opioid agonist treatment (separately) and naloxone kits distributed. Based on results from a similar analysis we conducted using the British Columbia Centre for Disease Control’s Overdose Cohort data, we hypothesize that OPS/CTSs had no effects on health service use and death rates once we control for co-occurring time-varying interventions (Panagiotoglou, 2022). Results from this study are pertinent to other communities with population demographics and needs different from Vancouver’s well studied Downtown Eastside.…”