Running 26.2 miles may make you sweaty and sore, but it won’t give you a heart attack, found a new study.
The finding offers a comforting counterpoint to the media frenzy that often follows when someone drops to the ground with cardiac arrest during a marathon. In the majority of cases, the new study found, athletes had a preexisting heart condition that would've likely become a problem even if victims had never signed up for a long-distance event.
On the other hand, even though exercise is essential for health, intense activity seems to be able to trigger fatal heart attacks in people who are already susceptible. So, anyone with a family history or suspicious symptoms should talk with a doctor before moving forward on a training program.
"Running these races is typically well tolerated and not risky despite reports of people dying," said Aaron Baggish, director of the Cardiovascular Performance Program at the Massachusetts General Hospital in Boston. "There's no question that exercise as part of daily life contributes to an overall healthy lifestyle and reduced cardiac risk."
"But exercising every day won’t completely protect you from heart disease," he added. "And if you're going to have an event, it's typically going to be while you're exercising."
Incidences of sudden death during a marathon get plenty of press, often leading people to assume that running long distances can be detrimental to health. But about two million people ran marathons and half-marathon events in the United States in 2010, more than double the number that competed in 2000.
To figure out the true risks of distance running for the heart, Baggish and colleagues began by tallying the number of cardiac arrests reported within an hour of crossing the finish line in marathon and half-marathon races around the country from 2000 through 2010.
Among the nearly 11 million people who ran long-distance races during that period, the researchers reported today in the New England Journal of Medicine, there were 59 cardiac arrests. Forty of those occurred after marathons, compared to 19 after half-marathons. More than 85 percent of victims were men, with a mean age of 42.
About twice as many people die today from post-marathon heart attacks today compared to the death toll a decade ago. But more people run marathons now, Baggish said, making the overall risk the same.
And the risk is generally low. Just one out of every 184,000 runners succumbs to cardiac arrest after a marathon, and one out of 259,000 dies from a heart condition.
That makes marathon running just as safe if not safer than recreational triathlons, college sports or even casual jogging. Rates of cardiac arrest and death were as much as five times higher for marathons as for half-marathons.
When the researchers took a closer look at those unlucky dozens who suffered heart attacks after their races, investigations showed that underlying heart disease was by far the biggest cause of death for runners. For younger runners, genetic problems were most common, particularly a thickening of the muscle called hypertrophic cardiomyopathy, which makes the heart electrically unstable. For older athletes, coronary artery disease was a bigger problem.
But hypertrophic cardiomyopathy also showed up in runners over age 40, and that is a new and interesting finding, said Michael Joyner, an exercise researcher at the Mayo Clinic in Rochester, Minn. It means that congenital heart problems might not surface until much later than researchers previously thought.
When it comes to marathons, Joyner suspects that race conditions could push runners at risk to a level of intensity that they may not have reached during training, which might push their hearts over the edge. He recommended that anyone with a family history of heart disease or with risk factors like high blood pressure, diabetes, obesity or smoking should see a doctor for a simple treadmill stress test before pounding the pavement.
Otherwise, fears of a heart attack should not stop people from starting running programs.
"In almost every circumstance, physical activity is protective against coronary disease," Joyner said. But "if you go out and run a marathon and you are not super-well trained, it might put you at risk of crossing a physiological line you didn't know existed."
The study also points out the importance for both athletes and spectators to learn basic CPR techniques, Baggish said. The difference between death and survival for runners in the new study, he said, depended on whether someone began CPR immediately after the runner went down.
And mouth-to-mouth is no longer necessary. The American Heart Association now recommends hands-only CPR at a rate of 100 compressions per minute directly over the sternum.
"Time and again, people drop, and the crowd and other runners watch and wait for paramedics," Baggish said. "That's why people die. This is a huge message to get across. Every responsible person in the community should know how to do CPR and know how to use it."