Study finds weather affects heart attack risk

Breaking News Emails

Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.

By Avichai Scher

A new study confirms what doctors have long asserted — cold weather is a risk factor for heart attacks. But the risk doesn’t stop with the cold. Low atmospheric pressure and the associated wind, rain and lack of sunshine also make heart attacks more likely, it seems.

The study, published Wednesday in JAMA Cardiology, looked at 3 million weather data points on the days corresponding with almost 275,000 heart attacks in Sweden. It covered a 15-year-period, from 1998 to 2013. Swedeheart, Sweden’s online cardiac registry, and the government’s expert weather institution, the Swedish Meteorological and Hydrological Institute, provided the extensive data.

Dr. David Erlinge, head of cardiology at Sweden’s Lund University and lead author of the study, said this is the largest-scale study he’s aware of on the effect of weather on cardiac events.

“People have been talking about weather and heart attacks for about 100 years,” he said. “With our robust data, we can separate out many more factors than just the cold.”

The study found that days with below-freezing temperatures (32 degrees Fahrenheit) had the highest incidence of heart attack. As temperatures rose closer to 40 degrees, heart attack rates went down. The north of the country, which has more snow and wind than the south, had generally higher rates.

But a deeper look at the data suggests that weather fluctuation could be the bigger factor. In the northern part of the country, the coldest region, heart attack cases did not correlate with temperature, but rather with increases in wind and snow. Looking at the whole country, the data specifically on the cold weather season, January to March, didn’t show a meaningful association with increased heart attack.

The finds indicate “an adaptation to long winters and low temperatures,” the study says.