Researchers in Japan set out to learn whether the weather on race day is connected to a runner’s chance of suffering a sudden cardiac arrest, a life-threatening emergency in which the heart abruptly stops pumping blood. To do this, they studied roughly 4.53 million people who ran in marathons across the country over about nine years (from April 2011 to March 2020). During that time, 75 runners experienced a sudden cardiac arrest. For each race, the team recorded conditions such as the outdoor temperature at the start and the level of air pollution, and then looked at how those conditions lined up with when and where these emergencies occurred.
The most striking result was that cooler weather, not hot weather, was linked to greater risk. For every 1 degree Celsius (about 1.8 degrees Fahrenheit) that the starting temperature dropped, the risk of sudden cardiac arrest went up. The researchers believe cold prompts the body to tighten its blood vessels and to shiver, which raises blood pressure and heart rate and forces the heart to work harder; cold can also cause subtle changes in the heart’s electrical rhythm. They did not find a meaningful link between air pollution and these events, though they noted that pollution levels were generally low during the races they examined.
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SOURCE: JACC Advances
Summary written by Adarsh Kabekkodu, SCAF intern