Spatial epidemiology of nonfatal overdose in a community-based cohort of marginalized women in Vancouver, British Columbia (2014–2022)

Background

Given limited data regarding the spatial epidemiology of overdose among women amid the current overdose crisis, we evaluated (1) changes in spatiotemporal clustering of overdose over time, (2) the association between residential proximity to overdose clusters and recent nonfatal overdose, and (3) the association between ‘risk environment’ features and residential proximity to overdose clusters.

Methods

Questionnaire data were from a merged community-based cohort of marginalized women who use drugs in Vancouver, Canada (09/2014–08/2022). Emerging hotspot analysis was used to classify residential proximity to spatiotemporal clusters of nonfatal overdose and kernel density estimation was used to visualize the spatiotemporal distribution of nonfatal overdose clustering over the 8-year study. Statistical analyses drew on bivariate and multivariable logistic regression using generalized estimating equations (GEE).

Findings

Over eight years, among 650 participants (3461 observations), 37·2 % experienced a nonfatal overdose at least once. Annual period prevalence of nonfatal overdose increased from 9·1 % in 2014–15 to 25·6 % in 2021–2022. The highest-density clusters were in Vancouver’s Downtown Eastside/Strathcona neighborhoods, where clusters became larger and more dispersed from 2016-onwards. Residential proximity to overdose clusters was associated with higher odds of recent nonfatal overdose. ‘Risk environment’ features of unstable housing, unsafe sleeping environments, and physical violence were associated with elevated odds of residential proximity to overdose clusters.

Interpretation

Marginalized women face a high and rising burden of nonfatal overdose, which is influenced by the ‘risk environments’ in which they reside. Scale-up of geographically tailored overdose prevention services, harm reduction, and programs addressing violence and housing are needed.