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Remind patients to bundle up to keep blood pressure down

Physician Practice Advisor, January 25, 2005

The risk of fatal heart attack and stroke peaks in the winter because, as a survival mechanism, blood vessels constrict in cold weather to conserve heat and maintain body temperature. With less room for the blood to flow, pressure rises. Many of these deaths could be prevented with simple precautions, according to a University of Florida (UF) study, published in the February issue of the American Journal of Physiology-Regulatory, Integrative and Comparative Physiology.

UF researchers found that a control group of 12 healthy mice kept at a constant 41 degrees Fahrenheit experienced a 50% increase in blood pressure after five weeks. However, 12 genetically engineered mice that lacked a receptor activated by the vessel-constricting hormone angiotensin II experienced only an 11% blood pressure increase under the same conditions, suggesting the receptor plays a key role in cold-induced blood pressure increases.

"We plan to collaborate with clinicians to look at blood pressure changes in hypertensive patients in all four seasons and see if renin-angiotensin system control is a good way to control cold-induced hypertension," says says researcher Zhongjie Sun, M.D., Ph.D. For now, physicians treating hypertensive patients with medication should be alert to seasonal changes in blood pressure, he says. People can take simple precautions to help lower risk, such as dressing in layers, easing into outdoor physical activity to minimize sudden changes in the heart's workload, and avoiding extreme exertion or heavy lifting.

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