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Study: Heart Attack Risk Increases When Temperature Drops Below Freezing

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PITTSBURGH (KDKA) - Is there such thing as heart attack season?

One cardiologist has seen a seasonal pattern.

"Just in general, when you look at statistics, heart attacks are more prevalent in winter," says Dr. Srinivas Murali, a cardiologist at Allegheny Health Network.

To look at this with more detail, researchers did a study in Sweden, where medical records are kept systematically.

All heart attacks go into a registry. In fact, they had data on 250,000 patients over 15 years.

(Photo Credit: KDKA)

The researchers then cross-referenced this information with weather observations, including temperature, length of daylight, wind velocity, and barometric pressure.

Short days, high winds and lower atmospheric pressure are all associated with more heart attacks, but most pronounced was the pattern with temperature.

"Bitterly cold temperatures put you at even higher risk," says Dr. Murali.

More heart attacks happened on days with temperatures below freezing. When the temperature was above 40 degrees, the rates of heart attack declined.

While this kind of study can't show cause and effect, there are reasonable explanations for the pattern.

It is possible the cold air against the skin and breathed into the lungs can cause a biochemical stress in the body, resulting in inflammation -- a set up for heart attack.

Also, narrowing of the blood vessels, a normal response to the cold, can raise the blood pressure, putting additional stress on the heart.

"If it is very cold, you have to protect yourself, make sure you are appropriately clothed, and if you are someone who has had a heart attack, or at risk for having a heart attack, because you have all kinds of other risk factors, you have to be particularly careful," Dr. Murali says.

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