Cold weather may increase heart attack risk: Winnipeg study

A cyclist pedals through the snow on Broadway Ave near Smith Street in Winnipeg, Tuesday, Dec.4, 2007.The forecast for the day was -11C with snow. THE CANADIAN PRESS/Winnipeg Free Press-Marc Gallant

A new study is giving Canadians another reason to fly south when the temperatures dip below 0 C.

According to research from the University of Manitoba, Canada's frigid winters may raise the risk of severe heart attacks by seven per cent for every 10 degrees the mercury drops.

The findings were presented at the European Society of Cardiology Congress in London on Sunday by Shuangbo Liu, a cardiology expert at the University of Manitoba in Winnipeg and a member of the research team that conducted the study.

The project shows “a clear relationship” between outdoor temperature and the risk of a severe heart attack, according to the researchers.

Liu and fellow researchers looked at every reported case of an ST-elevation myocardial infarction (STEMI)—the most severe type of heart attack—in Winnipeg over the past six years. Using data collected by Environment Canada, the researchers also compared the weather conditions of each day there was a reported heart attack.

“We demonstrated that there is a clear relationship between daily temperature and the risk of STEMI,” Liu said in an email to CTVNews.ca.

During the past six years, 1,817 STEMI heart attacks were reported in Winnipeg. Daily highs were the strongest predictor of the heart attacks, she said.

The study, conducted under the supervision of Dr. James Tam, the head of cardiology at the St. Boniface Hospital in Winnipeg, found that on days with a daily high of less than 0 C, heart attack rates were 0.94 per day. Heart attack rates were only 0.78 per day when the daily high was above 0 C.

These findings were consistent throughout all six years of research, Liu said.

What that translates to is that for every 10-degree drop in temperature, Winnipeggers were 7 per cent more likely to suffer a severe heart attack.

This risk, Liu said, could be predicted up to two days before the actual heart attack, making the methodology behind the study a useful tool for heart attack detection and prevention in the future.

While knowledge about how the weather affects cardiac health may help reduce heart attacks in the future, Liu said it is important to remember that the study only found an “association” between the two.

“We know that the cold is associated with increased heart attack risk, it does not necessarily mean that it is the direct factor that causes a heart attack,” Liu said.

With a population of approximately 700,000, Winnipeg is one of the coldest large cities in the world, making it an ideal place to carry out the study, Liu said.

The next step, she said, is to confirm the findings of the study beyond the city and look at ways the information can be useful to helping prevents heart attacks in the future.

“We need to validate this associate further, do further studies to look at the mechanisms of how cold is related to STEMI,” Liu said. “We need to increase awareness and preparedness.”