For just that reason, Dr. Larry B. Goldstein, director of the Duke Stroke Center in Durham, N.C., stressed that more work needs to be done to nail down the exact nature of the sunlight-stroke relationship.
"The findings don't surprise me, but it's important to know that this is a study of association," he said, "and association doesn't prove causality. The fact that here low sun exposure -- and presumably low sun exposure areas will also have low levels of vitamin D -- has been associated with a higher risk for stroke could potentially be explanatory."
"But in fact the authors are very careful to say that this is still an exploratory analysis," Goldstein noted. "So, even if this association turns out to be real there may a wide variety of potential explanations for it. We'll have to wait and see."
Another study also being presented at the stroke meeting revealed that those consuming more dietary vitamin D have an 11 percent lower risk of experiencing a stroke.
Research presented at medical meetings should be considered preliminary until published in a peer-reviewed medical journal.
For more on stroke risk, visit the National Stroke Association.
SOURCES: Leslie McClure, Ph.D., associate professor, biostatistics, department of biostatistics, University of Alabama at Birmingham; Larry B. Goldstein, M.D., professor, medicine, and director, Duke Stroke Center, Duke University Medical Center, Durham, N.C.; Feb. 1, 2012, American Stroke Association meeting, New Orleans
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