Unless you like hibernating during the winter season, you probably loathe the idea of traveling, going to work and doing outside chores amid the cold weather. And then there’s the risk of having a heart attack in cold temperatures.

A study published in May 2021 showed the seasonal variation in incidence and outcomes of cardiac arrest in non-hospital settings. As the leading cause of mortality among adults in the U.S., the researchers wanted to know which season documented more heart attacks.

After analyzing data from 122,870 adults who suffered out-of-hospital cardiac arrests, the team concluded that both incidence and mortality due to heart attack were higher during colder months. Meanwhile, they also found that the chances of surviving a heart attack were significantly higher in the summer season.

The exact statistics are difficult to determine, but scientists said U.S. cardiac arrests typically peak between December and January. But how does the cold weather trigger a heart attack?

In a discussion with Live Science this week, cardiologist Dr. Oliver Guttmann, of St. Bart’s Hospital in the U.K., explained the mechanism behind the higher incidence of cardiac arrest during the winter season.

According to him, the human body loses a lot of heat in cold weather, so the heart has to work harder to keep the body warm. For people who smoke, the elderly and individuals with heightened risk, this is a big challenge since overworking their hearts could trigger a heart attack.

“With less blood going to extremities like your fingers and toes, there is more pressure to pump blood around the rest of the body. [However] this means that your heart has to work harder, increasing both heart rate and blood pressure,” Guttmann said.

Cold weather promotes vasoconstriction, a condition wherein the blood vessels constrict, limiting blood flow in the extremities. When the vessels become narrow, the pressure increases, and this could cause fat buildup in arteries to burst.

Guttmann also noted how cold weather changes the viscosity of blood by making it thick. Thickened blood increases the chances of blood clot formation, which also causes a heart attack.

So how do you prevent a heart attack from happening during winter? Northwestern Medicine cardiologist Dr. Patricia Vassallo, M.D., shared some precautionary measures to lower the risk of cardiac arrest during the cold season.

According to her, it is important to wear winter clothes and stay warm and indoors as much as possible when there is no need to go outside. She also recommended avoiding alcohol, sticking to a heart-healthy diet and monitoring blood pressure. Last but not the least, talk to your physician beforehand if you are at heightened risk for any cardiac event.

Heart Attack
A person experiencing chest pain. Pexels