Cohort Profile: The Ontario Health Study (OHS).

Abstract

The prevalences of many chronic diseases—including cancer, cardiovascular disease, asthma and type 2 diabetes—have increased in Canada and many other countries over the past 30 years.1–4 In 2020, cancer and heart disease were the leading causes of death for Canadians, accounting for 48% of all deaths.5 About 37% of seniors (aged ≥65 years) have at least two common chronic diseases, with almost 50% of seniors aged ≥85 years suffering from multimorbidity.6 Chronic diseases are associated with high healthcare costs,7 rising complexity of care, long-term morbidity and mortality,8 and as such are major public health problems both in Canada and the rest of the world. A better understanding of their natural histories and complex and interrelated causes is needed to bring about the promise of disease prevention and early detection. Established to facilitate prospective observational health research, the Ontario Health Study (OHS; OntarioHealthStudy.ca) is a longitudinal population-based regional cohort study, designed to assess an extensive range of exposures and a wide range of health-related outcomes over a long period of time. It serves as an integrated platform for investigating the interplay of environment, lifestyle and ‘-omic’ (such as genomics, metabolomics, transcriptomics, proteomics) factors that increase individual and community risk of developing cancer and other common adult diseases. The intent is to engage participants in ongoing data collection over their lifespan, to follow them over time both actively and passively, and to make genomic, environmental, lifestyle and electronic health-related data available to the scientific research community. Derived variables, including data generated from biologic samples, are returned to the cohort to further enrich the data holdings.