Dual Epidemics in Toronto: Shared and Divergent Neighborhood Risks of COVID-19 and Opioid Mortality from a Joint...

Toronto experienced two overlapping public health emergencies during the COVID-19 pandemic, with a surge in opioid-related mortality. We assess how these mortality risks co-occurred and diverged across 158 neighborhoods from January 2020 to April 2023. We analyze monthly deaths using a joint Bayesian modeling framework with shared and outcome-specific spatial, temporal, and space-time interaction components. Neighborhood socioeconomic covariates include visible minority, low income, educational attainment, core housing need, and age structure. Our results identify spatial and temporal variations in mortality across Toronto and the socioeconomic drivers behind these variations. High shared spatial risks were observed in parts of northwest Etobicoke, York, and eastern Scarborough. Outcome-specific patterns diverged, with opioid deaths persistently clustered in downtown and west end hotspots, while COVID-19 mortality spatial risks were more spread out across Toronto. Temporally, COVID-19 mortality risks fluctuated throughout the pandemic, while opioid mortality remained relatively stable. Opioid mortality was associated with neighborhood deprivation, including low income (RR = 1.58, 95% CrI 1.34-1.87) and lower educational attainment (RR = 1.43, 1.20-1.70), and was highest in younger adults (25-44 years). COVID-19 mortality was most associated with neighborhood concentrations of older adults aged over 65 years (RR = 1.49, 1.17-1.91), with weak evidence for low income (RR = 1.38, 1.00-1.90). The visible minority concentration was inversely associated with opioid mortality (RR = 0.69, 0.53-0.90). Findings support integrated neighborhood-level responses, such as expansion of harm reduction and low-barrier treatment in opioid hotspots, sustained protections for older adults in higher COVID-19 mortality neighborhoods, and coordinating multi-sector efforts in high shared risk neighborhoods.