New York: The risk of cardiac arrest during a marathon or half-marathon is low, but has increased over the past decade, according to a US 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.
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.
That translates to a risk of 1 in 184,000 runners, with the risk of sudden death 1 in 259,000 -- which researchers characterized as "low overall."
That compares to 1 death per 42,770 college athletes per year and 1 in 7,620 seemingly-healthy middle-aged joggers.
The average age at cardiac arrest was 42, plus or minus 13 years. The fatal cases tended to be among younger runners and those who did not get cardiopulmonary resuscitation (CPR) right away.
The risk of cardiac arrest was more than five times higher for men than women, 9.0 per million entrants against 1.6 per million entrants, while the rate of cardiac arrests in marathons as opposed to half-marathons was 10.1 per million to 2.7 per million.
The rate of cardiac arrest among males nearly tripled from the first five years of the study to the last five years, from 7.1 to 20.3 per million entrants.
"The demographic, of men in particular, turning to marathons has changed considerably over the last 10 years. It used to be the purview of only healthy fit athletes," Baggish said.
"Now more folks who had been previously sedentary, have cardiovascular risk factors ... are turning to marathon running at an older age. They are probably the ones accounting for the increased risk."