Cold Weather Heart Warning

Stroke risk may rise as the temperatures fall

by Lisa O’Neill Hill | 07 Oct 2015 at 3:33 AM

Cold weather may be bad for your health if you have a common heart condition.

That’s the takeaway from a recent study by Taiwanese researchers that suggests people with atrial fibrillation have an increased risk of stroke when the weather is cool.

Atrial fibrillation (AF) is a type of irregular — or “racing” — heartbeat that increases someone’s risk for stroke by 500 percent, according to the National Stroke Association. The condition can cause blood to collect in the heart and form a clot that can travel to the brain.

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The study by Dr. Tze-Fan Chao, a cardiologist at Tapei Veterans General Hospital and the National Yang-Ming University in Taiwan, suggests that cool climates may provide an underrated health risk that deserves more attention. The study indicated that cold weather might promote blood clots to form in the left atrium of the heart, increasing stroke risk.

“Our study shows a clear association between temperature and risk of ischemic stroke in patients with AF,” Chao said in a release issued by the European Society of Cardiology.

The study looked at the incidence of ischemic stroke — the most common kind of stroke caused when a clot disrupts blood flow to the brain — among nearly 290,000 patients. Chao compared daily temperatures in six regions of Taiwan between 2000 and 2011.

Stroke  risk increased by 10 percent in spring and 19 percent in winter compared to summer.

The researchers averaged the temperatures in the six regions to calculate the country average. They estimated the risk of ischemic stroke for each month and season. When the average temperature was below 68 degrees, stroke risk significantly increased compared to days with an average temperature of 86 degrees, the study found.

The risk of ischemic stroke increased by 10 percent in spring and 19 percent in winter compared to summer. Researchers didn’t find a significant difference between stroke risk in summer and autumn.

If you have atrial fibrillation, are you better off living in sunny Southern California than braving icy Minnesota winters?

Not necessarily.

Dr. Michael Guirguis, a Harvard-trained emergency medicine physician, said the study shows an association, not a causation.

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Cold weather does not cause ischemic strokes in patients with atrial fibrillation, he said.

“It’s possible that in cold months, patients are less active and stay inside, which is a risk factor for blood clots,” Guirguis told LifeZette.

And treatment modalities for atrial fibrillation may be different in Taiwan than the standard of care in Europe or the United States, Guirguis said. In the U.S., most people with atrial fibrillation are on some type of blood thinner, such as aspirin or Coumadin. That may not be the case in Taiwan, which could affect the stroke rates.

“This being said, I'm not sure if I lived in an area where it gets extremely cold in the winter months, I would sell my house and uproot my family for a location that is much warmer,” Guirguis said.

Chao said the study’s findings could help reduce stroke risk in people with atrial fibrillation.

“This suggests there may be an opportunity to predict strokes in AF patients before they happen, and put preventive measures in place such as adequate anticoagulants and reducing cold exposure through protective clothing and heating homes in winter,” he said.

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