Cold Weather Can Raise Blood Pressure
Bundle Up, Dress in Layers in Chilly Settings
Jan. 19, 2005 -- Want an easy, inexpensive way to help avoid high blood pressure? Then bundle up this winter.
Cold temperatures can raise blood pressure, say University of Florida researchers. For people with year-round high blood pressure, chilly weather can make matters worse, sending their blood pressure even higher than normal.
Even healthy people aren't off the hook. They also tend to have higher blood pressure in the winter, say the researchers, who included Zhongjie Sun, MD, PhD, an assistant professor of physiology and medicine.
Blood Pressure: Widespread Problem
High blood pressure is a year-round problem for nearly one in three American adults -- but a third of them don't know it, says the American Heart Association. That's dangerous, since high blood pressure is a risk factor for heart attack, stroke, and other health problems.
High blood pressure is defined as 140/90 mmHg or more. A borderline condition called prehypertension is a reading of 120/80 to 130/89. Normal blood pressure is lower than 120/80.
Winter is America's worst season of the year for heart disease, say the researchers. With that in mind, they studied how cold weather raises blood pressure. Their findings appear in the February issue of the American Journal of Physiology -- Regulatory, Integrative, and Comparative Physiology.
The researchers bred mice that lacked a gene related to blood pressure. Without the gene, the mice didn't have receptors for a hormone called angiotensin ll, which constricts blood vessels and raises blood pressure.
Normally, the hormone docks at special receptors to do its work. But the mice didn't have the receptors, leaving the hormone homeless. That could make it harder for blood pressure to spike when exposed to cold, the researchers thought.
That's exactly what happened. Sun's team lowered the temperature in the cages of the mice to 41 degrees Fahrenheit. The mice had no bedding to nest in for warmth.
After five weeks, the genetically altered mice had an 11% increase in blood pressure. Under the same conditions, blood pressure soared 50% in the normal mice after five weeks.
It doesn't take a massive cold front to raise blood pressure. The experiment's temperature was mild, compared with a U.S. winter weather map. How much does blood pressure rise in the cold? That depends on factors including length of exposure, dress, activity level, and the climate someone is used to.