For the study, researchers identified all new immigrants to Ontario, Canada, over a 12-year period and matched them to people of the same age and gender who had lived in Ontario for at least five years. A total of 966,000 new immigrants were matched to more than 3.2 million long-term residents. The participants were age 16 to 65 at the start of the study, with an average age of 34.

The researchers then followed all of the participants for an average of about six years. During that time, there were 933 strokes among the new immigrants and 5,283 strokes among the long-term residents. This is a rate of 1.7 strokes per person per year in new immigrants and 2.6 strokes per person per year in long-term residents, or a 30 percent lower rate for new immigrants.

The results were the same after adjusting for income level, smoking, and history of other diseases such as high blood pressure and diabetes.

"Recent immigrants to Canada and the U.S. face many stressors as they adapt to changes in their diet, jobs, housing and relationships which may adversely affect stroke risk," said study author Gustavo Saposnik, MD, MSc, with St. Michael's Hospital, the University of Toronto and a member of the American Academy of Neurology. "Other studies have shown that compared to people born in those countries, recent immigrants to Canada and the U.S. may have lower rates of diseases such as high blood pressure. On the other hand, the lower prevalence of hypertension and other risk factors such as diabetes and smoking among new immigrants may decrease their vascular risk. We evaluated which of these two competing factors (psychosocial stress associated to the new environment vs. health immigrant effect) prevail."

There are several theories why immigrants may be healthier than long-term residents: Those willing to undergo the stress of immigration are usually in good health prior to immigrating; the medical examination required of all potential immigrants screens out unhealthy candidates; and immigrants who experience poor health may return to their home country for support.

"More research to determine whether the risk of stroke in immigrants 'normalizes' to the level seen in longer-term residents may help shed light on undiscovered risk factors for stroke," said Bradley S. Jacobs, MD, MS, of Wright State University Boonshoft School of Medicine in Dayton, Ohio, who wrote an editorial accompanying the study.

The study was supported by a grant from the Heart and Stroke Foundation of Ontario.

Note: If no author is given, the source is cited instead.

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