Cold Weather Linked With Heart Risk Factors, Heart Attack, In New Studies

Here's some not-so-great news, considering many of us will be moving into chillier weather in the upcoming months: New research shows that cold weather might not be good for our hearts.

Two new studies, presented at the European Society of Cardiology Congress 2013, show that cold weather not only seems to be linked with heart risk factors, but it also seems to be associated with more heart attacks.

The first study, conducted by Dr. Pedro Marques-Vidal of Switzerland, shows that heart risk factors, including high blood pressure, cholesterol and waist circumference, seemed to be higher than average in the winter months -- particularly January and February -- and lower than average in the summer months -- particularly June, July and August. The findings are based on data from 10 studies from seven European countries, which included a total of 107,090 people between the ages of 35 and 80.

For example, systolic blood pressure levels (the top number on a blood pressure reading) were 3.5 millimeters of mercury lower, on average, during the summer than the winter. Meanwhile, waist circumference was 1 centimeter, on average, smaller during the summer than the winter. Total cholesterol was 0.24 millimoles per liter lower, on average, during the summer than the winter.

"We observed a seasonal variation in waist circumference but BMI did not change throughout the year," Marques-Vidal said in a statement. "We have no clear explanation for this finding. Total cholesterol may increase during the winter because of changes in eating habits. There was no seasonal variation in glucose, probably because several cohorts did not collect blood samples in the fasting state. We have begun a study on seasonality of food intake which may help explain these findings."

In the second study, conducted by Belgian researcher Marc Claeys, an association was found between lower temperatures and increased heart attack risk.

Specifically, heart attack risk went up by 7 percent for every 10 degree Celsius drop in temperature. However, researchers were unable to find any link between heart attack risk and air pollution, contrary to other research. The study is based on data from 15,964 people who had experienced heart attack, with an average age of 63.

"A potential mechanism to explain the increased risk of coronary events associated with decreasing temperature is the stimulation of cold receptors in the skin and therefore the sympathetic nervous system, leading to a rise in catecholamine levels," Claeys explained in a statement. "Moreover, increased platelet aggregation and blood viscosity during cold exposure promotes thrombosis and clot formation."

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