Your risk of heart attack spikes after winter snowstorms, shovelling snow: Canadian study

With much of Canada in winter’s grip, new research is warning that heavy snowfall and shovelling after a snowstorm increases risk of going to the hospital for a heart attack, especially for men.

In a new study published Monday in the Canadian Medical Association Journal, scientists out of the University of Montreal warn that Canadians should make sure they aren’t overexerting themselves during these brisk months.

“We studied more than 20 years of data for the province of Quebec and we found a rather robust signal for increased cardiac events…and cardiac death associated with heavy snowfall,” study co-author, Dr. Brian Potter, told Global News.

“It didn’t entirely surprise us. There were already hints in the literature it was there. What struck me was how robust the findings were. We found it was true whether we looked at heavy snowfall, duration of snowfall, the number of consecutive days of significant snowfall. This was true regardless of whether you were older, you were young, you had risk factors or you didn’t have risk factors,” Potter said.

Tweet This Click to share quote on Twitter: "It didn't entirely surprise us. There were already hints in the literature it was there. What struck me was how robust the findings were. We found it was true whether we looked at heavy snowfall, duration of snowfall, the number of consecutive days of significant snowfall. This was true regardless of whether you were older, you were young, you had risk factors or you didn't have risk factors," Potter said.

READ MORE: Why your risk of heart attack, stroke or chest pain spikes 2 days after a snowstorm

Potter said this isn’t the first time research on snowfall and heart health has been analyzed. But his team gained access to valuable data – two separate databases with the health information of more than 200,000 people who were admitted to hospital. Sixty-eight thousand died from heart attacks between 1981 and 2014.

Potter’s team zeroed in on the winter months and matched them with weather reports and snowfall measurements.

Men made up about 60 per cent of hospital admissions and deaths tied to heart attack between November and April. The day after a heavy snowfall is when these hospital visits spiked – this is when one-third of men turned up in hospital for heart-related issues.

READ MORE: Here’s how women’s heart attack symptoms differ from men’s

This wasn’t the case for women, though. Potter said he hypothesizes it’s because women don’t shovel snow.

It’s the “most plausible” explanation in his mind. The study concedes its limitation: they didn’t have data on who was shovelling snow, how much snow is being shovelled or whether snow removal was manual or done with, say, a snow blower.

The researchers say the takeaway message is to raise awareness about the risk of heart attack post-snowstorm. Shovelling snow is a demanding workout taking up more than 75 per cent of the maximum heart rate, especially if you’re working with heavy tools, the study suggests.

READ MORE: Have high pain tolerance? Don’t ignore these signs of a ‘silent’ heart attack

Earlier this month, U.S. scientists said that it’s two days after a healthy dose of snowfall that hospitals see a spike in heart attacks, strokes and chest pain.

The Harvard School of Public Health study suggests the climb is as steep as 23 per cent.

Why the two-day delay? The scientists guess it’s because snowstorms keep people indoors and away from potential hazards. There could also be a delay – people may not want to head to hospital in the middle of a whiteout.

READ MORE: What floor you live on may determine cardiac arrest survival, Canadian study suggests

Snow shovelling could also be a factor. When the snow settles, that’s typically when people head outdoors to clear their driveways.

The medical community always pointed to a link between the cold season and an increase in heart attacks, but researchers say that people in warmer locations aren’t any less vulnerable.

They suggest that other factors are at play, too: shorter days, falling out of good habits and daily exercise all wreak havoc with our health and immune systems.

The dip in temperatures makes blood vessels constrict, driving up your blood pressure. Your heart is forced to work overtime as your blood’s gateways narrow, decreasing blood flow.

READ MORE: Male heart attack patients receive faster care than women, Canadian study suggests

Another “interesting phenomena” about winter is that the body’s blood itself thickens, making it more likely to clot when exposed to the cold.

Winter is also notorious for the flu season as influenzas and other bugs make their rounds through the population.

Read the latest findings in the CMAJ.

carmen.chai@globalnews.ca
Follow @Carmen_Chai

Watch below: A study from Quebec suggests heavy snowfalls could be increasing the risk of a serious health episode. Su-Ling Goh reports.

2:37 New study suggests link between snowfall amounts and heart attack risk