Heart risk during marathons low, but rising: study

The risk of cardiac arrest during a marathon or half-marathon is low, but has increased over the past decade, according to a U.S. study of nearly 11 million race entries.

Men face a greater risk than women, and full marathons are more dangerous than half marathons, with enlarged hearts and blocked arteries pegged as the biggest causes, according to findings published in the New England Journal of Medicine.

The results suggest that runners and their doctors need to realize that heart disease can take its toll even on runners who otherwise seem to be the picture of health, said coauthor Aaron Baggish of Massachusetts General Hospital.

"Being a runner is one of the best ways to stay healthy and reduce your risk of disease. But it's not 100 percent protective," Baggish told Reuters Health.

"The people who get into trouble are the people who are either born with, or develop, through the normal aging process, heart disease."

Participation in long-distance races has rapidly increased in recent years. In the United States alone, participation has doubled over the past decade to about 2 million in 2010.

Participation in long-distance running races has increased annually in the United States. In 2010, there were approximately 2 million participants in marathon and half-marathon races, as compared with fewer than 1 million participants in 2000. This increase has been driven in part by heightened public awareness of the health benefits of regular physical exercise. However, the growth of long-distance running has been accompanied by studies documenting post-race cardiac dysfunction and numerous reports of race-related cardiac arrest. These unexpected tragedies attract considerable media attention and have led to concerns regarding the health risks of this activity.

Sudden death in young, competitive athletes has been well characterized. However, these data may not apply to participants in long-distance running races, who are an older population with different cardiovascular risk factors and underlying medical conditions. Prior studies have examined cases of cardiac arrest from only one or two events or have lacked detailed clinical information. The incidence, clinical profiles, and outcomes of cardiac arrests that occur during long-distance running races therefore remain uncertain.

The Race Associated Cardiac Arrest Event Registry (RACER) was designed to address these issues. The registry collected data from the most recent decade of long-distance running races to determine the incidence, clinical profile, and outcomes of cardiac arrest in these events.

The findings were based on a database of all U.S. marathons, which are 42 km or 26.2 miles long, and half-marathons, run from January 2000 through May 2010. It includes information on 10.9 million race registrations.

In all, there were 59 cases of cardiac arrests, 42 of them fatal, during the races or within an hour afterward.