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The cold, hard facts about shovelling: A third of heart attacks happen day following snowstorms

National Post logo National Post 2017-02-13 Postmedia News
snow-2: Montreal residents shovel their cars from the snowbanks in 2008. © Pierre Obendrauf/Postmedia News/File Montreal residents shovel their cars from the snowbanks in 2008. snow-1: Ronald Lavis digs out a car in the Montreal suburb of Saint-Laurent on Monday after up to 23 centimetres of snow fell in some parts of the city. © Phil Carpenter/Postmedia News Ronald Lavis digs out a car in the Montreal suburb of Saint-Laurent on Monday after up to 23 centimetres of snow fell in some parts of the city.

MONTREAL — Heart specialists from Ottawa through the Maritimes can expect to be busier for the next few days — 16 per cent busier, to be exact.

A new Quebec study looking at every major snowfall between 1981 and 2014 found these cold, hard facts: A snowfall of 20 centimetres increases the odds of being hospitalized by 16 per cent — and of dying from a heart attack by 34 per cent.

One third of heart attacks happened a day following a storm and 10 per cent after snowfalls of five centimetres or more. The association was even stronger after snowfalls lasting two to three days.

That’s exactly what has been happening in eastern Canada — 28 centimetres fell in Ottawa Sunday, 29 cm in Montreal between Sunday and Monday, 35 cm in Fredericton Monday

And then there is Halifax, where a heart-rending 45 cm fell on Monday alone, with some parts of Nova Scotia expecting up to 70 cm by the time it all ends — hopefully — on Tuesday.

Published by the Canadian Medical Association Journal, the study mined 33 years of data on snowfall, heart failure and death, taking into account confounding factors such as obesity, diabetes, smoking and high blood pressure.

Researchers compared days with zero snowfall to days with 20-centimetre dumps. Looking at the Quebec winter months of November through April, from 1981 to 2014, Auger’s team found a strong relationship between the amount of snow and hospitalizations and deaths due to heart attacks.

The study included nearly 200,000 people: 128,073 individuals who were admitted to hospital with an MI, and 68,155 deaths due to MI. Not all the people who died made it to a hospital first.

“We didn’t go to their homes to find out whether they were shovelling or not,” lead researcher Nathalie Auger of the Quebec Public Health Institute explained. “We looked at the relationship between snowfall and risk of MI (myocardial infarction or heart attack).”

“It’s the first study that looks at actual risk in population,” said Auger, an epidemiologist affiliated with University of Montreal Hospital Research Center.

“If you had a small heart attack and didn’t present to a hospital and didn’t die, we would be missing you,” she said.

The study found the increased risk of hospital admission or death due to MI was primarily among men.

“We don’t know why that is,” Auger said. “It’s possible that men shovel more than women. Or that women do it in a way that’s less risky or causes less exertion. Snow shovelling is a demanding cardiovascular exercise requiring more than 75 per cent of the maximum heart rate, particularly with heavy loads.”

Advanced age, smoking, obesity and diabetes are known to contribute to heart disease, which accounted for eight million deaths worldwide in 2013, and such deaths are higher in countries with extreme weather.

Some experts suggest a snowstorm combined with cold weather and hard work — straining to move wet and heavy snow — can cause a sudden surge in blood pressure and heart rate.

“In the big picture, very few people who shovel will actually have a heart attack,” she said. However, those with risk factors should shovel “slowly and with less exertion.”

The authors noted limitations to the paper, including lack of data on sex-specific shovelling habits, size of areas shovelled or whether snow removal was manual or with a snowblower.

With files from Charlie Fidelman, Montreal Gazette

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