Sue Leahy remembers one particular Christmas day vividly. At the time, Leahy, now president of the American Safety and Health Institute in New Paltz, N.Y., was a paramedic on call.
"A man had shoveled snow on Christmas Eve and thought he had pulled a muscle, so he let it alone for the night," she recalls. When the pain failed to subside the following morning, he dialed 911. "He actually apologized for disturbing us on the holiday," she says. But he was right to make the call, she says, "he did not pull a muscle; he had suffered a heart attack."
Visit WebMD's Heart Disease Health Center
Diagnosed? Find out more
Attack: Get Information From the Cleveland Clinic
Rehabilitation: Get Information From the Cleveland Clinic
for Clinical Trials? Check here
Test Your Heart
A classic heart attack is marked by pain in the chest that may radiate down the left arm, but sometimes it may feel more like a muscle pull, she explains. The pain usually lasts more than a few minutes and can wax and wane in intensity. "The heart is a muscle, and the pain could be from a clogged artery in the heart," she says, but the pain can radiate, making it appear to be a pulled muscle in the back or neck.
"When in doubt, go to the emergency room or call 911 and get it checked out," she says. Leahy's advice is especially prudent in winter months when research has shown heart attacks are more common and more severe. A report in the Dec. 13, 2004, issue of Circulation: Journal of the American Heart Association found that the rate of heart disease-related deaths (as well as deaths from other causes) rose sharply between Dec. 25 and Jan. 7. In fact, the death rate peaked on Christmas Day and New Year's Day.
Exactly why winter is prime time for heart attack is still an evolving story, but many theories exist and possibly overlap.
During the winter months, "there is a change in the ratio of daylight hours to dark hours, which changes the hormonal balance, and the hormones involved, such as cortisol, can lower the threshold for a cardiovascular event," explains Stephen P. Glasser, MD, a professor of preventive medicine at the University of Alabama at Birmingham School of Medicine, in Birmingham, Ala.
The Plot Thickens
But that's not all that's going on. Cold temperatures cause arteries to tighten, restricting blood flow and reducing the oxygen supply to the heart, all of which can set the stage for a heart attack.
"In cold weather, there is more oxygen demand by the heart because it is working harder to do the work and maintain body heat," Glasser says.
Glasser says studies have shown that heart attacks and complications related to heart disease occur more frequently in the morning hours.
Research suggests that the early-morning rise in blood pressure, or "a.m. surge," that occurs in most people may dramatically increase the risk of having a heart attack or stroke. "In the winter, people tend to exert themselves or do yard work in the morning because it gets dark earlier," he tells WebMD.
"This shift of activities to morning hours adds to the normal circadian variation in mornings --further increasing heart rate, blood pressure, and the hormones that lower the threshold for a cardiovascular event," he says.