Looking at the medical literature, it is easy to see that winter can be a dicey season for heart patients.
Many studies, some going back decades, have documented climbing heart attack rates during the winter. Some refer to the phenomenon as the Christmas coronary. To what extent winter raises the risk is a matter of debate. But one large study, using data on hundreds of thousands of heart attacks documented in the National Registry of Myocardial Infarction, found that 53 percent more cases were reported in winter than in summer. A pattern of decreasing occurrence of cases from winter to fall to spring and then summer was found across gender, age and geographic area.
The primary culprit, many believe, is temperature. Cold weather narrows arteries and raises blood pressure, stressing the heart. Physical strain and ruptured plaques caused by shoveling snow are also commonly cited.
But in a recent study presented at an American Heart Association conference, two researchers, Dr. Bryan Schwartz and Dr. Robert Kloner, found that the risk increases even in warm climates. Analyzing death certificates in seven regions with different climates — Los Angeles, Texas, Arizona, Pennsylvania, Massachusetts and others — they found that cardiovascular deaths rose up to 36 percent between summer and winter, regardless of climate and temperatures.
Dr. Schwartz, a clinical cardiovascular fellow at the University of New Mexico, said a number of things may be involved, including the spread of influenza and other respiratory infections. Seasonal affective disorder stemming from fewer daylight hours, as well as less healthy eating and exercise habits around the winter holidays, may also play a role.
THE BOTTOM LINE
Heart attack rates climb in the winter, though cold weather may be just one of several reasons.
-by Anahad O’Connor
A version of this article appeared in print on 11/13/2012, on page D5 of the NewYork edition with the headline: Really? | The Claim: Cold weather raises the risk of heart attacks..