Incidence of Stroke in Immigrants to Canada: A Province-wide Retrospective Analysis

Background and Objectives

To evaluate the association between immigration status and stroke incidence.

Methods

We conducted a retrospective cohort study of 8 million adults (15% immigrants) residing in Ontario, Canada, on January 1, 2003, with no history of stroke or TIA. Participants were followed up until March 31, 2018, to identify incident stroke or TIA, defined as hospitalization or emergency room visit. We calculated adjusted hazard ratios (HRs) of stroke or TIA in immigrants compared to long-term residents using cause-specific hazard models, adjusting for demographics and comorbid conditions. We evaluated whether the association varied by age, stroke type, or country of origin of immigrants.

Results

During 109 million person-years of follow-up, we observed 235,336 incident stroke or TIA events. Compared to long-term residents, immigrants had a lower rate of stroke or TIA (10.9 vs 23.4 per 10,000 person-years, HR 0.67, 95% confidence interval [CI] 0.66–0.68). This was true across all age groups and stroke types, with an HR in immigrants vs long-term residents for ischemic stroke of 0.71 (95% CI 0.69–0.72), for intracerebral hemorrhage of 0.89 (95% CI 0.85–0.93), for subarachnoid hemorrhage of 0.85 (95% CI 0.81–0.91), and for TIA of 0.53 (95% CI 0.51–0.54). The magnitude of the reduction in stroke risk associated with immigration status was less pronounced in immigrants from the Caribbean (HR 0.95, 95% CI 0.91–1.00), Latin America (HR 0.85, 95% CI 0.82–0.91), and Africa (HR 0.80, 95% CI 0.74–0.85) than in those from other world regions.

Discussion

Immigrants have a lower rate of stroke or TIA than long-term residents with variation by age, stroke type, and country of origin. This knowledge may be useful for developing targeted primary stroke prevention strategies.

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