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It does not matter if you spend the winter months mowing the lawn or brushing snow off the windshield of your car. New evidence says that in either case, you are more likely to die from a heart-related issue in the winter than during other seasons.

The idea that cold climates are somehow linked to a higher number of heart-related deaths, while warmer temperatures offer some protection, is a popular belief. But a study presented on Wednesday at the American Heart Association's Scientific Sessions, taking place in Los Angeles, has found that the theory does not add up.

"It means that perhaps temperature or climate is ... not as important a factor as it was once believed to be," said Bryan Schwartz, a cardiology fellow at the University of New Mexico who conducted the study with Robert Kloner at the Heart Institute of Good Samaritan Hospital in Los Angeles.

In the study, the researchers examined death certificates from 2005 to 2008 from seven different areas of the United States that have warm, moderate and cold climates during the winter: Los Angeles County, Texas, Arizona, Georgia, Washington, Pennsylvania and Massachusetts.

They found that heart-related deaths, which include those from heart attack, heart failure, cardiovascular disease and stroke, rose an average of 26 to 36 per cent during the winter months in the areas that were studied. The researchers noted that none of the areas were statistically distinct in terms of overall heart-related death rates.

Although the reasons are not entirely clear, Schwartz said there are several likely explanations as to why heart-related deaths rise in the winter, regardless of climate. Seasonal influenza, which does not discriminate based on climate, may be a major factor, he said. That is because the flu can cause serious heart-related problems in some of those who contract it. Emerging evidence suggests that people who get the flu shot are less likely to suffer heart attacks.

Fewer daylight hours and a rise in seasonal affective disorder, which causes people to experience a type of depression in winter months, could also be contributing factors. In addition, many North Americans simply are not as healthy in the winter as they are in the summer and may be more apt to eat more and exercise less, Schwartz said.

That is not to say a cold climate has no impact on the overall risk of death. There is solid evidence suggesting that shovelling snow is linked to an increased risk of heart attack. But what is clear from the study, Schwartz said, is that heart-related risk of death is also present in warmer climates during the winter.