Opioid use disorder diagnosis risk and neighbourhood-level marginalisation: a population-based retrospective cohort study

Background Marginalisation has been proposed as a risk factor for the development of opioid use disorder (OUD), an important element of Canada’s ongoing opioid epidemic. In this study, we examined the relationship between neighbourhood-level dimensions of marginalisation and risk of OUD in Ontario, Canada. Methods We conducted a retrospective cohort study from 1 January 2016 to 31 December 2022 using population-level administrative data. Neighbourhood-level marginalisation was measured by three dimensions of the Ontario Marginalisation Index (households and dwellings, material resources and age and labour force). Incident OUD diagnoses were extracted using International Classification of Diseases, 10th Revision (ICD-10), Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5), Ontario Health Insurance Programme fee codes and drug identification numbers for opioid agonist therapy. Modified (robust) Poisson regression using generalised estimating equations produced risk ratios (RRs) to assess the association between neighbourhood-level marginalisation and OUD in multivariate analyses. Results A random sample of 221 267 individuals was taken from all eligible Ontarians (n=10 806 807). A total of 1222 incident OUD diagnoses were made, indicating a rate of 844.38 diagnoses per 1 000 000 person-years. In multivariate models comparing the lowest and highest marginalisation quintiles, neighbourhood households and dwellings (RR=1.60, 95% CI 1.33 to 1.92), material resources (RR=2.03, 95% CI 1.68 to 2.45) and age and labour force (RR=1.48, 95% CI 1.27 to 1.72) were significantly associated with risk of incident OUD. Conclusion Risk of incident OUD is associated with neighbourhood-level marginalisation, a relationship that occurred with and without adjusting for relevant demographic and clinical factors. Addressing social disadvantage should be prioritised in research and public health interventions amidst the ongoing opioid crisis.