It happens every winter: Heart attacks strike countless people who push themselves to shovel snow after a storm.
But new research finds over-exertion isn’t only to blame. In fact, cold air can chill the heart’s oxygen supply -- putting people with heart disease at greater risk.
Penn State researchers said cardiac patients may not be able to compensate for their bodies' higher demand for oxygen when inhaling cold air, making shoveling and other outdoor winter activities dangerous.
"This study can help us understand why cold air is such a trigger for coronary events," said Lawrence I. Sinoway, director of the Heart and Vascular Institute at Penn State College of Medicine.
Sinoway’s findings -- reported in the American Journal of Physiology, Heart and Circulatory Physiology – were based on examinations of the heart function of adults in their 20s and their 60s while exercising in cold weather.
What they found is breathing cold air during exercise can cause “uneven” oxygen levels in the heart.
“A healthy body generally corrects for this problem and redistributes blood flow, making sure the heart continues to function properly,” Sinoway said. “In people with heart problems -- such as coronary artery disease -- this may not be the case.
"If you are doing some type of isometric work and you're breathing cold air, your heart is doing more work -- it's consuming more oxygen," he said.