Shoveling snow linked to one third of heart attacks: study

A new study from the University of Montreal Hospital Research Centre finds that up to one third of heart attacks suffered by men during the winter season may be associated with snow shoveling, an activity which is known to put a heavy stress load on a person’s cardiovascular system.

The study published in the Canadian Medical Association Journal looked at 128,000 hospital admissions in the province of Quebec between 1981 and 2014 including 68,000 deaths from heart attack and correlated the data with weather reports on snowfalls between the months of November and April of those years. Researchers found that the likelihood of a heart attack increased after a snowfall for men but not for women and stated that their results speak to the importance of health initiatives and public awareness of the dangers of snow shoveling.

“We suspect that shoveling was the main mechanism linking snowfall with MI,” says Dr. Nathalie Auger, epidemiologist with the Quebec Public Health Institute and the University of Montreal Hospital Research Centre and study co-author. “Men are potentially more likely than women to shovel, particularly after heavy snowfalls. Snow shoveling is a demanding cardiovascular exercise requiring more than 75% of the maximum heart rate, particularly with heavy loads.”

The findings say that a snowfall of 20 centimetres increased the odds of being hospitalized by 16 per cent and of dying from a heart attack by a full 34 per cent. The data showed that one third of heart attacks during the winter months occurred the day after a snowstorm, with the association being even stronger for storms that lasted two or three days.

The health risks of snow shoveling are well known, as the activity combines tough physical exertion with cold temperatures which constrict the blood vessels and thicken the blood, creating dangerous conditions for those already showing certain risk factors for heart attack such as smoking, high blood pressure, obesity and lack of physical activity.

A study by the U.S. Nationwide Children’s Hospital found that between 1990 and 2006, 1,647 fatalities were recorded in the United States from cardiac-related injuries associated with snow shoveling. The number is likely much higher in reality, says Barry Franklin, cardiologist and director of preventative cardiology and cardiac rehabilitation at the William Beaumont Hospital in Royal Oak, Michigan. “I believe we lose hundreds of people each year because of this activity,” says Franklin to the BBC.

Franklin and his colleagues tested healthy young men while shoveling snow and found that heart rates and blood pressure increased more than when the men exercised on a treadmill. “Combine this with cold air, which causes arteries to constrict and decrease blood supply, you have a perfect storm for a heart attack,” he says.

Franklin advises anyone over the age of 55 to not shovel snow and says that those who are at greatest risk are those with habitually sedentary lives with suspected coronary disease who go out once a year to clear snow. “If you must do it, push rather than lift the snow, dress in layers, take regular breaks indoors and don’t eat or smoke before shoveling,” he says.