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This cohort can be used retrospectively to observe trends in service utilization, healthcare integration, healthcare costs and patient outcomes. It also facilitates the design of observational studies to mimic a prospective design.<\/jats:p>\n          <\/jats:sec>\n          <jats:sec>\n            <jats:title>Methods<\/jats:title>\n            <jats:p>This study used linked administrative data from ICES to create a cohort of 137,035 individuals who received at least one prescription of methadone or buprenorphine\/naloxone between 2014 and 2022. Data were linked using de-identified personal health numbers. Variables included age, sex, rurality, income, homelessness, and mental health conditions. Regional differences in OAT use, retention, and mortality were analyzed.<\/jats:p>\n          <\/jats:sec>\n          <jats:sec>\n            <jats:title>Results<\/jats:title>\n            <jats:p>Of the cohort, 56.1% began OAT after 2014. Southern Ontario participants more often started on methadone (53.2%), while Northern Ontario patients favored buprenorphine\/naloxone (62.7%). Northern patients were younger, more likely to be female, live in rural areas, and face homelessness. The death rate was higher in Southern Ontario (22.1%) than in Northern Ontario (13.2%). Retention declined over time, with 73.4% of patients remaining in treatment at the study's end.<\/jats:p>\n          <\/jats:sec>\n          <jats:sec>\n            <jats:title>Conclusions<\/jats:title>\n            <jats:p>The findings highlight regional disparities in OAT delivery and emphasize the need for region-specific strategies, particularly in rural areas, to improve retention and reduce mortality.<\/jats:p>\n          <\/jats:sec>","DOI":"10.1007\/s10654-025-01202-3","type":"journal-article","created":{"date-parts":[[2025,1,27]],"date-time":"2025-01-27T09:33:55Z","timestamp":1737970435000},"page":"235-243","update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["Cohort profile: the provincial opioid agonist treatment cohort in Ontario, Canada"],"prefix":"10.1007","volume":"40","author":[{"given":"Kristen A.","family":"Morin","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mark R.","family":"Tatangelo","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Shreedhar","family":"Acharya","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8769-1785","authenticated-orcid":false,"given":"David C.","family":"Marsh","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"297","published-online":{"date-parts":[[2025,1,27]]},"reference":[{"issue":"9810","key":"1202_CR1","doi-asserted-by":"publisher","first-page":"55","DOI":"10.1016\/S0140-6736(11)61138-0","volume":"379","author":"L Degenhardt","year":"2012","unstructured":"Degenhardt L, Hall W. Extent of illicit drug use and dependence, and their contribution to the global burden of disease. Lancet. 2012;379(9810):55\u201370.","journal-title":"Lancet."},{"key":"1202_CR2","unstructured":"Federal, provincial, and territorial Special Advisory Committee on the Epidemic of Opioid Overdoses. Opioid- and Stimulant-related Harms in Canada. Ottawa:: Public Health Agency of Canada; 2023 [Available from: https:\/\/health-infobase.canada.ca\/substance-related-harms\/opioids-stimulants\/."},{"key":"1202_CR3","unstructured":"Ontario Drug Policy Research Network. Ontario Opioid Indicator Tool Toronto, ON: ODPRN; 2023"},{"key":"1202_CR4","unstructured":"[updated March 2023. Available from: https:\/\/odprn.ca\/ontario-opioid-indicator-tool\/"},{"key":"1202_CR5","doi-asserted-by":"publisher","first-page":"66","DOI":"10.1016\/j.drugalcdep.2018.11.024","volume":"195","author":"VA Pear","year":"2019","unstructured":"Pear VA, Ponicki WR, Gaidus A, Keyes KM, Martins SS, Fink DS, et al. Urban-rural variation in the socioeconomic determinants of opioid overdose. Drug and Alcohol Dependence. 2019;195:66\u201373.","journal-title":"Drug and Alcohol Dependence."},{"key":"1202_CR6","doi-asserted-by":"publisher","DOI":"10.1016\/j.drugalcdep.2021.108717","volume":"224","author":"MF McLaughlin","year":"2021","unstructured":"McLaughlin MF, Li R, Carrero ND, Bain PA, Chatterjee A. Opioid use disorder treatment for people experiencing homelessness: A scoping review. Drug Alcohol Depend. 2021;224: 108717.","journal-title":"Drug Alcohol Depend."},{"key":"1202_CR7","doi-asserted-by":"crossref","unstructured":"Morin KA, Eibl, JK, Gauthier G, Rush B, Mushquash C, Lightfoot NE, Marsh DC. A cohort study evaluating the association between concurrent mental disorders, mortality, morbidity, and continuous treatment retention for patients in opioid agonist treatment (OAT) across Ontario, Canada using administrative health data [pre-print]. 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Approval was granted by the Laurentian University Research and Ethics Board number 6020852.","order":3,"name":"Ethics","group":{"name":"EthicsHeading","label":"Ethical approval"}},{"value":"Consent to participate and publish was not obtained for this study. We utilized secondary data from ICES (Institute for Clinical Evaluative Sciences). As a prescribed entity under Personal Health Information Protection Act (PHIPA), ICES is authorized to collect personal health information from health organizations without consent, specifically for the purpose of evaluating and monitoring Ontario\u2019s health system. Access to this research data is granted only after approval by ICES\u2019 Privacy Office and a Research Ethics Board (REB). Once approved, ICES provides research-ready, linked, and de-identified data. All personal identifiers are irrevocably removed before the data is made available to researchers, making written consent unattainable.","order":4,"name":"Ethics","group":{"name":"EthicsHeading","label":"Consent to participate and publish"}}]}}