January 11, 2012

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By Amanda Gardner

WEDNESDAY, January 11, 2011 ( — Last November, two apparently healthy young men—one 40 years old, the other just 21—collapsed during the running of the Philadelphia marathon and were later pronounced dead, apparently of heart-related causes.

The news was shocking but familiar: In the previous two months alone, a 35-year-old firefighter had collapsed with a stopped heart as he neared the finish line of the Chicago Marathon, and a 32-year-old had suffered a fatal heart attack in the homestretch of a half-marathon in Montreal.

Recurring headlines like these may leave the impression that deadly heart problems during long-distance races are common. In reality, the odds of experiencing cardiac arrest and sudden death during a race are extremely low, according to a new study published this week in the New England Journal of Medicine.

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Researchers combed through news databases for mentions of cardiac arrest—not to be confused with heart attacks—during marathons and half-marathons, then verified those accounts with the survivors (or next of kin), using medical records and autopsy data when available. They found just 59 cases of cardiac arrest, 42 of them fatal, between 2000 and 2010—a decade in which 11 million runners took part in nearly 11,000 marathons and half-marathons in the United States.

That translates into one cardiac arrest per 184,000 runners and one sudden death per 259,000 runners per year. To put those odds in perspective, roughly one in every 6,200 licensed drivers in the United States dies in a traffic accident each year.

"Marathons and half-marathons are generally safe, well-tolerated activities," says lead author Aaron Baggish, M.D., an assistant professor of cardiology at Harvard Medical School and Massachusetts General Hospital, both in Boston.

The grueling races may be safer than everyday running, in fact. As the study notes, the rate of sudden death among regular joggers has been estimated at one in 7,620 per year.

What's more, the 29% survival rate seen in the study is dramatically better than the 8% figure usually cited for out-of-hospital cardiac arrests, probably because the many spectators on hand at road races can start CPR right away—"one of the most important determinants of whether people live or die," Baggish says.

Next page: Men appear to be at greater risk

Despite the small number of incidents, Baggish and his colleagues were able to discern some broad patterns in the data. Cardiac-arrest rates were higher among men than women, for instance, and higher in marathons than in half-marathons.

And the causes of cardiac arrest seemed to vary with age. Among younger runners, a genetic thickening of the heart muscle (hypertrophic cardiomyopathy) was typically to blame, while among older runners the most common culprit was a type of heart disease characterized by stable artery blockages that can be present, unnoticed, for long periods of time.

"That means something was there for months to years," Baggish says. "People can live with [a blockage] until they have that bad day [when] they just don't get enough blood."

These blockages can be detected with tests, Baggish says. He urges aspiring distance runners to discuss heart disease risk factors (such as high blood pressure and cholesterol) with their doctors, and to undergo an exercise stress test if needed.

Cardiac arrest is different—and far more deadly—than a heart attack. In cardiac arrest the heart stops beating, interrupting the flow of blood, whereas during heart attacks a ruptured artery plaque causes a blood clot that reduces blood flow to the heart.

Heart attacks can also be a problem among long-distance runners, as a letter to the editor in the same issue of the journal makes clear. The letter details the cases of three middle-aged men with no diagnosed heart disease who suffered ruptured plaques and coronary blood clots soon after crossing the finish line of the 2011 Boston Marathon.

Exercise may increase the risk of plaque rupture and blood clots, the authors note. It can also benefit your heart, of course.

"The truth is—and this is incontrovertible—is that running and regular physical exercise keeps you healthy and lowers the risk of heart disease," Baggish says. "But it's not perfectly protective."

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