When a runner dies during a marathon because their heart stops, it's big news -- and can be scary to the 2 million runners who participate in U.S. long-distance events each year.
However, the risk of cardiac arrest during long-distance races is relatively low, according to new research. A cardiac arrest occurs when the heart stops beating, and it's generally more serious than a heart attack.
Over a 10-year period, 59 runners, or 1 in 184,000 participants in half or full marathons, suffered cardiac arrest, says researcher Aaron Baggish, MD, associate director of the Cardiovascular Performance Program at Massachusetts General Hospital. He is also the cardiologist for the Boston Marathon. There were nearly 11 million participants during the decade studied.
Those who run a full marathon, 26.2 miles, are at higher risk of heart problems than those who run the half, he found. Men are at higher risk than women.
"It appears the half marathon is safer and better tolerated than the marathon," says Baggish. "Most of the problems we saw were marathon-related."
The study is published in The New England Journal of Medicine.
The new research, believed to be the first comprehensive study of marathon and half-marathon participants, may change the stereotypes. "The public perception is that marathons and half marathons are dangerous endeavors," Baggish says.
Veteran runners, on the other hand, may feel overly protected because of their healthy lifestyle, he says.
While the number of race-related deaths due to cardiac arrest has risen, "the increase in the number of cardiac deaths only parallels the increased number of participants," Baggish tells WebMD.
In 2000, fewer than 1 million participated in U.S. long-distance races. In 2010, 2 million did.
Baggish and his team tracked cases of cardiac arrest in half marathons and marathons in the U.S. from Jan. 1, 2000, through May 31, 2010.
They interviewed survivors or the family members of those who died. They reviewed medical records. They looked at post-death data.
Forty of the cardiac arrests occurred during marathons; 19 during half marathons.
Eighty-six percent of those who suffered cardiac arrest, or 51 of the 59, were men. The average age of those who had cardiac arrest was 42. Cardiac arrest was most likely to occur during the last quarter of the event.
Of those 59 cardiac arrests, 42 were fatal. Baggish says that death rate -- 71% -- is better than the 92% rate generally found when cardiac arrest occurs, when people are at home or in other isolated areas.
He credits the medical services at races and bystanders who performed CPR with this higher survival rate.
Next, Baggish looked at the causes. He had enough medical information to evaluate the cause for 31 of the 59 runners. An abnormal thickening of the heart muscle, known as hypertrophic cardiomyopathy, was often the confirmed or probable cause of death.
Among those who survived, underlying heart disease was the most common problem. Baggish found the risk of cardiac-related death over the 10-year period was 1 per 259,000 long-distance runners. Other research suggests that this risk is equal to or lower than that for other physical activity such as triathlons, college athletics, and jogging, he says.