Impact of marginalization on characteristics and healthcare utilization among people with substance use disorder in Ontario, Canada, before and during the COVID-19 pandemic: A cross-sectional study

To describe and compare the characteristics of people with SUD and their use of healthcare services in two ways: 1) across varying levels of marginalization and 2) before and during the pandemic. We conducted a population-based cross-sectional study using administrative data from Ontario, Canada. We included individuals age 16+ with a recorded diagnosis of SUD between June 2018-2019 (pre-pandemic) and June 2021-2022 (during-pandemic). Baseline sociodemographic and clinical characteristics and use of healthcare services were enumerated across the five quintiles of the Ontario Marginalization Index. 259,497 pre-pandemic and 276,459 during-pandemic people with SUD were identified. Over 40% belonged to the two highest marginalization quintiles (Q4/Q5). Most had an outpatient visit with similar percentages across quintiles, however the number of visits increased with increasing marginalization (pre-pandemic: mean 8.5 visits in Q1 vs 13.0 visits in Q5; during-pandemic: mean 9.5 in Q1 vs 13.4 in Q5). There was no consistent pattern in percent of people who sought alcohol-related outpatient care, however more marginalized people sought drug-related outpatient care (pre-pandemic: 19.1% in Q1 vs 31.7% in Q5; during-pandemic: 18.7% in Q1 vs 32.5% in Q5). Almost half of people with SUD had an emergency department (ED) visit, of which more belonged to higher marginalization quintiles (pre-pandemic: 43.5% in Q1 vs 49.8% in Q5; during-pandemic: 41.4% in Q1 vs 49.3% in Q5). SUD prevalence and most health service utilization remained similar from pre- to during-pandemic. Increasing marginalization was associated with increased use of healthcare among people with SUD. Future research should aim to further explore the complex relationship between marginalization and substance use.