Risk of premature stroke in recent immigrants (PRESARIO) Population-based matched cohort study

Background: New immigrants to North America, most of whom are under age 50 years, exhibit fewer risk factors for cardiovascular disease than their native-born counterparts, yet the stress of resettlement may conceivably place them at higher risk of stroke. We determined the risk of acute stroke associated with recency of immigration. Methods: We completed a population-based matched cohort study in Ontario, the largest province in Canada, from April 1, 1995, to March 31, 2007. Overall, 965,829 new immigrants were matched to 3,272,393 long-term residents by year of birth, sex, and location. New immigrants were identified as new recipients of universally available public health insurance, and long-term residents were those insured for 5 years or longer. Results: The mean age of the participants at study entry was about 34 years and the total number of observed strokes was 6,216 after a median duration of follow-up of about 6 years. The incidence rate of acute stroke was 1.69 per 10,000 person-years among new immigrants and 2.56 per 10,000 person-years among long-term residents (crude hazard ratio [HR] 0.66, 95% confidence interval [CI] 0.62-0.71). After adjusting for age, income quintile, urban vs rural residence, history of hypertension, diabetes mellitus and smoking, and number of health insurance claims, the HR for stroke was 0.69 (95% CI 0.64-0.74). Similar risk estimates were seen for both ischemic and hemorrhagic stroke subtypes. Conclusion: New immigrants appear to be at lower risk of premature acute stroke than long- term residents. This finding does not appear to be explained by the availability of health care services or income level. Neurology (R) 2010; 74: 451-457