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Tuesday, August 3, 2010
Is Distance Running Really Good For Your Heart?
By guest blogger: Kreton Mavromatis, MD, Assistant Professor of Medicine, Emory University, Director of Cardiac Catheterization, Atlanta VA Hospital
It's Sunday morning, July 4th and I have just returned from running a 10K race and I am feeling good. I run approximately 3 or 4 days per week, and I run a race or two, including a half-marathon, each year, mainly to serve as a training goal. My motivation for running is primarily so that I can afford to eat more food, my favorite daily activity. However, as a cardiologist, seeing people with heart attacks from occluded coronary arteries day-in and day-out, I have always believed that running (and exercise in general) is good for my vascular health. After all, doesn't running lower blood pressure and cholesterol, and haven't studies shown that people who exercise more live longer? In fact, prospective epidemiological studies have suggested a dose related effect, implying more exercise of greater intensity is better.
To my dismay, however, several recent studies have suggested that running may not be good for my heart or arteries after all. Mohlenkamp et al showed that 108 apparently healthy marathon runners had more coronary artery calcium (which is found in coronary artery atherosclerosis) than patients matched for age and Framingham risk score (a commonly used measure of a person's risk for cardiovascular disease based on their risk factor profile). Furthermore, they showed that the amount of coronary artery calcium, as well as the number of marathons run, was directly associated with myocardial (heart) damage, which was detected in 12% of the marathon runners. Finally, four of the runners had cardiovascular "events" over the next 2 years, all of whom had high levels of coronary artery calcium. Similarly, Schwartz et al. showed that 25 marathoners had more coronary artery plaque than 25 non-marathoners who had similar ages, blood pressure and cholesterol levels.
These studies are far from conclusive. The marathon runners may have had more predisposition to coronary artery disease than the non-runners despite similar Framingham risk scores, perhaps due to prior lifestyle differences (i.e. smoking, diet) or a more extensive family history of such disease. On the other hand, there are plausible mechanisms by which running could increase vascular disease. Intensive exercise is well-known to increase oxidative stress and inflammation, which are fundamental to the development of coronary artery disease.
Runners like me like to believe that running is good for our heart and blood vessels, based on the principle of "use it or lose it". However, maybe the cardiovascular system is more like a car (and just about everything else), the more "mileage" it has, the more likely it is to break down.