OVERLAND PARK, Kan. -- The Hospital Hill Run, a popular half-marathon, is coming up Saturday in Kansas City, so it's a good time to think about running and your heart. A growing body of evidence suggests that marathon running over decades is not good for the heart in the long run.
Jason Mills has always enjoyed running. For eight years, he ran marathons.
"I loved just kind of challenging my body to that extent," Mills said.
But the 2012 Boston Marathon was his last marathon. He quit when tests showed he had plaque build-up in heart arteries. His doctor told him that extreme exercise was putting him at higher risk for a heart attack.
Mills doesn't think marathon running itself contributed to the plaque build-up.
"I think for me it's mostly genetic," he said.
But research by Dr. James O'Keefe of Saint Luke's Mid-America Heart Institute suggests that long-distance running over decades does accelerate plaque build-up. It also appears to stiffen the heart muscle.
"If you're exercising hard, like one, two, three hours a day, with respect to cardiovascular health and longevity, you might as well be sitting on the couch," O'Keefe said.
Dr. O'Keefe says the risks are the same as they are for couch potatoes. In addition, new research from Sweden finds that men who exercise extensively for many years are more likely to have atrial fibrillation, an irregular heartbeat.
The doctor says the findings in no way discount the value of exercise. Just do it moderately.
"Above an hour of hard exercise per day, you're probably missing out on some of the benefits of less extreme exercise," said Dr. O'Keefe.
Mills' running is less extreme now. He goes 15 to 20 miles a week.
"For me, it's just gotta be moderate now. And no matter how you slice it, marathoning is never moderate. You know, it's a hard, taxing event on the body," he said.