Are Older, Dedicated Runners Risking Their Lives?

Science has good news and bad news for older runners: You're faster and stronger than ever. But your exertions may be shortening your life.

The dispiriting conclusion that the toll long-distance running takes on the cardiovascular system negates any health benefits is based on an analysis of recent studies of fitness and aging by the British medical journal Heart. In one study, researchers tracked 52,600 adults for 30 years and found that recreational runners had a 19 percent lower death rate. But those who ran 20 miles per week or more had mortality rates equal to those who didn't run at all.

In other words, while regular jogging appears to deliver significant cardiovascular benefits, the stress to the body caused by constant running may do almost the opposite. Similarly, a separate study found that runners who ran faster than 8 miles per hour (7:30 miles or speedier) had the same mortality risk as average adults; however, those who ran regularly, but more slowly, did have a decreased death rate.

(MORE: Why It's Never Too Late to Start Running)

"Running too fast, too far and for too many years may speed one's progress toward the finish line of life," sports cardiologist James O'Keefe of the St. Luke's Mid America Heart Institute in Kansas City writes in Heart.

Years of earlier study had led experts to believe that long-distance runners faced few significant risks. Only 1 in 100,000 marathoners die during races, for example, and it has long been established that regular cardiovascular exercise can prolong life and ward off heart disease, stroke, dementia and other conditions.

But the latest data are part of a growing body of evidence that so-called "extreme" athletes may be at high risk of developing cardiac abnormalities, including atrial fibrillation, which is a major cause of stroke, and coronary artery calcification, which is more typically found in people with sedentary lifestyles. "Chronic extreme exercise appears to cause excessive 'wear-and-tear' on the heart," O'Keefe writes.

"The belief is that more is better, but we're learning that more is not better in this case," he has said. "We're not born to run. We're born to walk."

But while excessive running may pose risks, O'Keefe adds, the sedentary lifestyle remains a critical health challenge. "You need to be moving your body rather than sitting. Every chance you get, move."

(MORE: The Fiftysomething Workout: 10 Top Fitness Apps)

O'Keefe has previously studied the cardiovascular risks of "chronic excessive endurance exercise" and other potential pitfalls of the extreme-sports lifestyle, especially for older athletes. But his new conclusions have been hotly debated by fellow cardiologists and running bloggers. Among other concerns, critics argue that since endurance runners do not represent a high percentage of all adult runners, it's difficult to draw any generalizations about their health or mortality. Others point out that runners run not just to prolong their lives, but because it feels great, keeps them fit and delivers the thrill of competition.

O'Keefe, 56, is a former champion of shorter, or "sprint distance," triathlons. But he now believes his training regimen was shortening his life, so he no longer runs more than 20 miles a week or at a speed faster than eight minutes per mile. "After age 50, pushing too hard is probably not good for one's heart or longevity," he told The Wall Street Journal.

The co-author of O'Keefe's analysis, cardiologist Carl Lavie of the John Ochsner Heart and Vascular Institute in New Orleans, told the Wall Street Journal that he runs faster only when training for a road race. "When I race I know the risks," he said. "That's all we're trying to do: Let people know the risks and make up their own minds."