Researchers say there may be a link between weather and the risk for stroke.
They analyzed local climate trends and hospital records on millions of Americans. They found that cold weather, high humidity and big daily temperature swings seem to land more people in the hospital with strokes. As it got warmer, risk fell.
Doctors say there are biological reasons to believe the trend. Blood vessels constrict in cold weather, which can raise blood pressure. High humidity can cause dehydration. Extreme weather puts stress on the body, making the heart work harder.
The study by researchers from Yale, Harvard and Duke universities was discussed Wednesday at a stroke conference in San Diego.