Differential patterns by area-level social determinants of health in COVID-19 related mortality and non-COVID-19 mortality: a population-based study of 11.8 million people in Ontario, Canada

Background — Social determinants of health (SDOH) have been associated with COVID-19 outcomes. We examined differential patterns in COVID-19-related mortality by SDOH accounting for confounders and compared these patterns to those for non-COVID-19 mortality.

Methods — Residents of Ontario, Canada aged ≥20 years were followed from March-01-2020 to March-02-2021. COVID-19-related death was defined as death within [-7,30] days of a positive COVID-19 test. Area-level SDOH from 2016 Census included: median household income; proportion with diploma or higher educational-attainment; proportion essential workers, racially-minoritised groups, recent immigrants, apartment buildings, and high-density housing; and average household size. We examined associations between SDOH and COVID-19-related mortality using cause-specific hazard models, treating non-COVID-19 mortality as competing risks, and vice-versa.

Results — Of 11,810,255 individuals, we observed 3,880(0.03%) COVID-19-related deaths and 88,107(0.75%) non-COVID-19 deaths. After accounting for individual-level demographics, baseline health, and other area-level SDOH, the following area-level SDOH were associated with increased hazards of COVID-19-related death (hazard ratios[95% confidence intervals]: lower income (1.30[1.04-1.62]), lower educational-attainment (1.27[1.07-1.52]), higher proportions essential workers (1.28[1.05-1.57]), racially-minoritised groups (1.42[1.08-1.87]), apartment buildings (1.25[1.07-1.46]), and large vs. medium household size (1.30[1.12-1.50]). In comparison, areas with higher proportion racially-minoritised groups were associated with a lower hazard of non-COVID-19 mortality (0.88[0.84-0.92]).

Conclusions — Area-level SDOH are associated with COVID-19-related mortality after accounting for demographic and clinical factors. COVID-19 has reversed patterns of lower non-COVID-19 mortality among racially-minoritised groups vs. their counterparts. Pandemic responses should include strategies (e.g., ‘hotspot’ and risk-group tailored vaccination) to address disproportionate risks and inequitable reach of, and access to, preventive interventions associated with SDOH.