Does shoveling snow really put you at risk of a heart attack?

Answers to your questions about the news.
Feb. 9 2010 6:23 PM

Death by Driveway

Can shoveling snow kill you?

A man shovelling snow.
Digging out

The National Weather Service is forecasting as much as 20 inches of new snow in Washington, D.C. and 18 inches near Philadelphia by Wednesday—the second major snowfall to affect the Middle Atlantic region in the last several days. The House canceled debates scheduled for Tuesday night, airlines are canceling flights, and—as always happens when there's snow on the ground—journalists are writing stories about shoveling-induced heart attacks. "Shoveling Snow Can Cause Heart Problems" (WHIZ News); "shoveling snow can be incredibly dangerous for someone with a cardiac condition" (Staunton News Leader); "heart attacks among shovelers are a major concern" (Pittsburgh Post-Gazette). Is there a real connection between shoveling and cardiac trouble?

Yes. Studies published in the Lancet and the American Journal of Cardiology, among other outlets, show that the incidence of heart failure goes up in the week after a blizzard. The Lancet study, based on death certificates in eastern Massachusetts after six blizzards from 1974-78, demonstrated that ischemic heart disease deaths rose by 22 percent during the blizzard week and stayed elevated for the subsequent eight days, suggesting that the effect was related to storm-related activities, like shoveling, rather than the storm itself. Similarly, the AJC article, based on medical examiner records from three Michigan counties, found that there were more exertion-related sudden cardiac deaths in the weeks during and after blizzards, and that 36 of the 43 total exertion-related deaths occurred during or shortly after snow removal.

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It's possible that snow-shoveling is no more dangerous than any other physically draining activity—that the same individuals who die while clearing their driveways could just as well succumb to a vigorous jog. The post-blizzard spike could be attributed to the fact that sedentary people with potential heart problems have no choice but to engage in heart-pounding work with a shovel, whereas other aerobic activities (at other times of year) can be put off or skipped altogether.

There is some reason to think that snow-shoveling is particularly tough on the cardiovascular system. Whereas jogging leads to a fairly steady rise in blood pressure, shoveling is an intense, rapid exercise that may result in a blood pressure spike. Cold weather, in itself,  increases the risk of heart attack, since the shoveler expends energy just to keep warm and may have more trouble breathing. Researchers have also pointed out that shovelers hold their breath when they bend down, which can lead to a sudden change in heart rate. One study of 10 sedentary men with no history of cardiac disease found that their heart rates while shoveling rose above the recommended upper limit for aerobic exercise.

The absolute risk of death-while-shoveling is low. An often-quoted statistic holds that 1,200 American die from a heart attack or other cardiac event during or after a blizzard every year, and that snow-shoveling is frequently to blame. This figure is sometimes attributed to the Centers for Disease Control, although an agency spokeswoman could not verify its source. Even if this statistic were correct, it's nothing in comparison to the total number of annual heart-related deaths. According to the American Heart Association, there are 425,425 deaths per year from coronary heart disease.

Got a question about today's news? Ask the Explainer.

Explainer thanks Johnny Lee of American Heart Associates, Maggie Francis of the American Heart Association, and Karen Hunter of the Centers for Disease Control and Prevention. Thanks also to reader Michael Carrasco for asking the question.

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Juliet Lapidos is a staff editor at the New York Times.

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