The findings point out "the critical importance of early life exposures to lifelong health," said Dr. Mary Cushman, associate professor of medicine and pathology at the University of Vermont, lead author of a study published earlier this year that showed that conventional risk factors for stroke, such as obesity and diabetes, did not fully account for the regional differences.
"Other factors, such as genetic factors, environmental toxins and learned behavior [in youth, for example, from parents] could play a role," Cushman said.
The study had its weaknesses, she said, including "the inability to finely measure region of residence over lifespan and the reliance on administrative data for analysis."
"All we measured was where people were born," Glymour acknowledged. "But most people born in a state stay there at least through adolescence."
Still, the new study had a more solid base than earlier ones reporting the same association, Glymour said. One such study, which she led, had a much smaller sample and relied on self-reported stroke. "This one used strokes reported on death certificates and had national coverage," Glymour said.
More work is needed to determine why the stroke rate is higher in the South and to find ways to reduce the risk both regionally and nationally, she said.
"We think that understanding the causes of the phenomenon would be helpful in general to reduce stroke rates," Glymour said.
For more information on stroke, see the U.S. National Library of Medicine.
SOURCES: M. Maria Glymour, Sc.D., assistant professor, society, human development and health, Harvard School of Public Health, Boston; Mary Cushman, M.D., associate professor, medicine, University of Vermont, Burlington; Dec. 1, 2009, Neurology/i>
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