Jan. 11, 2012 -- 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.
Marathons & Cardiac Arrest: Analysis
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.
Marathons & Cardiac Arrest: Perspective
The study findings offer valuable information, says Ravi Dave, MD, a cardiologist at Santa Monica-UCLA Medical Center & Orthopaedic Hospital in Los Angeles. He reviewed the study findings for WebMD.
The findings will help doctors determine which tests may help identify potential problems in runners, he says. An echocardiogram, for instance, can help identify the heart muscle thickening, Dave says. This test uses sound waves to create a picture of the heart.
A stress test, done on a treadmill, can help identify those who have severe blockages, he says.
Those planning to run long-distance events should get a medical checkup, Dave says. "You need to indicate to the physician the reason for the checkup: that you are running," he tells WebMD.
It is better, Dave says, for beginners to do a half marathon before progressing to a full marathon.
Marathons & Heart Attacks: Advice
"Every person new to the sport should talk to their doctor about [heart] risk," Baggish says. A doctor will order tests based on factors such as a runner's age and family history of heart problems, he says.
Long-distance running, he says, "is overall a safe activity." However, ''leading the running lifestyle doesn't completely protect you from heart disease."
Baggish reports no disclosures. Some co-authors report receiving consulting fees from Lupin Pharmaceuticals and Furiex Pharmaceuticals, grant funding from GlaxoSmithKline and Novartis, and lecture fees from Merck, Pfizer, Abbott, and others.