New Immigrants Have Lower Acute Stroke Risk By Allison Gandey
Medscape Medical News
February 5, 2010 — Recent immigrants are less likely to have premature acute stroke than long-term residents of North America, a new study shows. The approximately 30% lower relative risk held even after adjusting for multiple risk factors, report researchers.
"Our findings verify the presence of a healthy immigrant effect in relation to stroke risk," note the group led by Gustavo Saposnik, MD, from the Stroke Outcome Research Canada Working Group at the University of Toronto. "Policies are needed that aim to preserve the healthier state of new immigrants, while continuing to focus on lowering stroke risk among all adults."
The study known as PRESARIO or Risk of Premature Stroke Associated with Recency of Immigration to Ontario was a population-based, matched, retrospective cohort study.
Results are published in the February 9 issue of Neurology and were released early online.
In an accompanying editorial, Bradley Jacobs, MD, from Wright State University in Dayton, Ohio, called the work compelling. "The epidemiologic study of disease in immigrants holds promise for elucidating causes of and contributors to disease not readily evident in a general population," he noted. Similar Risk for Ischemic and Hemorrhagic Strokes
Study participants were enrolled in the Ontario Health Insurance Plan, which covers most aspects of health care with no user fee.
Canada has one of the highest rates of immigration in the world. According to the 2006 Census, 28% of the total population of Ontario is foreign born — this is the highest rate among all Canadian provinces.
Investigators matched more than 960,000 new immigrants to more than 3,200,000 long-term residents by year of birth, sex, and location. Immigrants were identified as new recipients of universally available public health insurance, and long-term residents were those insured for 5 years or longer.
The mean age of the study participants was about 34 years, and the total number of observed strokes was 6216 after a median duration of follow-up of about 6 years.
Dr. Saposnik and his team found that new Canadians were less likely to have a stroke. Investigators observed similar risk estimates for both ischemic and hemorrhagic events. Table 1. Incidence of Acute Stroke
Population
Rate Per 10,000 Person-Years
Immigrants
1.69
Long-term residents
2.56
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The hazard ratio was 0.66, with a 95% confidence interval of 0.62 to 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 hazard ratio for stroke was 0.69, with a 95% confidence interval of 0.64 to 0.74.
Investigators report that although new Canadians sustained fewer strokes, those who did have one had slightly longer hospital stays and a marginally higher likelihood of transfer to a long-term care facility.
The researchers note a number of limitations to their study. For example, they did not have access to information on the study participants' educational level or lifestyle. They also did not have measures of blood pressure, blood glucose, serum lipids, or stroke severity.
Clearly, the study authors write, having detailed information of the country of birth and some basic physical and social measures of new immigrants could help explain why they have fewer strokes than long-term residents but may do worse after having a stroke.
The researchers point out that new immigrants to North America are typically younger than 50 years and have fewer risk factors for cardiovascular disease. Still, they note, the stress of resettlement could conceivably place them at higher risk for stroke.
This was not the case in the current population. The study authors acknowledge that many questions remain.
"Perhaps genetics, diet, weather, infection, or lack of infection may help to maintain a lower risk of stroke after immigration," Dr. Jacobs added.
"What we learn," the study authors note, "could translate into long-term health benefits for the whole population, irrespective of their immigrant status." Coauthor Dr. Eva Lonn has received funding from AstraZeneca, GlaxoSmithKline, Merck Serono, Novartis, Sanofi-Aventis, and Abbott. She receives research support from Roche, the Canadian Institutes of Health Research, and the Heart and Stroke Foundation of Canada. Neurology. 2010;74:451-457.
