More people die due to heart attacks during winter than summer, according to researchers from the Good Samaritan Hospital in Los Angeles.

"This was surprising because climate was thought to be the primary determinant of seasonal variation in death rates," said Dr. Bryan Schwartz, lead author of the study, in a press release.

Researchers examined records of deaths occurred between 2005 and 2008 in seven different locations across the U.S. - Los Angeles County, CA, Texas, Arizona, Georgia, Washington, Pennsylvania and Massachusetts.

Between summer low and winter peak, deaths due to heart disease, stroke, and cardiovascular diseases jumped up from 26 percent to 36 percent.

One of the hypotheses given by the researchers is that cold weather might have constricted the blood vessels and raised blood pressure.

People don't take care of their health in winter as much as they do in the summer, and the lack of physical activity and weight gain during winter months adds to the heart disease risk, researchers say.

The study was presented at the American Heart Association's Scientific Sessions 2012.