Men are more likely to have a heart attack after a snowfall, and it's probably from the exertion of shoveling snow, Canadian researchers reported Monday.
They found a slight increase in both heart attacks and deaths from heart attack in Quebec after a storm. The likelihood went up with each extra day of snow, they reported in the Canadian Medical Association Journal.
"We suspect that shoveling was the main mechanism linking snowfall with myocardial infarction (heart attack)," Dr. Nathalie Auger of the University of Montreal Hospital Research Center and colleagues wrote.
"Men are potentially more likely than women to shovel, particularly after heavy snowfalls. Snow shoveling is a demanding cardiovascular exercise requiring more than 75 percent of the maximum heart rate, particularly with heavy loads," they added.
The team studied 128,000 heart attack cases between 1981 and 2014, and more than 68,000 people who died.
A single day of snowfall raised a man's risk of heart attack by just less than 1 percent, they wrote, and it raised his risk of dying from a heart attack by 12 percent.
Eight inches of snowfall raised the risk 16 percent compared to a day in the same month that did not have snow, they reported, and men were one-third more likely to die of a heart attack the day after an eight-inch snowfall, compared to a dry day.
Women were not more likely to either have heart attacks or to die of them after snow, the team found.
Snow shoveling is hard. It's not a daily activity, and it strains the heart, Auger's team said. People often exhale hard with their mouths closed while lifting a heavy shovel full of snow, a dangerous habit called the Valsalva maneuver, they noted.
Using the arms intensively and repetitively, especially while standing upright, can also raise the risk that a piece will break off from a clogged artery, the researchers noted. Cold temperatures make blood vessels constrict, which adds to the danger.
It might not only be shoveling that does it. People using snow blowers have also been reported to have higher rates of heart attack, the Canadian team noted.
The National Safety Council has some advice for how to safely shovel snow:
- Do not shovel after eating or while smoking
- Take it slow and stretch out before you begin
- Push the snow rather than lifting it
- If you do lift it, use a small shovel or only partially fill the shovel
- Lift with your legs, not your back
- Do not work to the point of exhaustion
- Talk to a doctor before shoveling if you have a history of heart disease
- Stop immediately if you feel dizzy or tightness in the chest