The two faces of marathon running
ESSEN, GERMANY. It is well established that regular physical exercise reduces the risk of cardiovascular disease, but it is equally well established that vigorous exercise increases the short-term risk of coronary events (heart attack and stroke), especially among elderly people not accustomed to exercise. A group of German researchers have now taken a look at the cardiovascular risk profile of 108 apparently healthy male marathon (42 km) runners aged 50 years or older and with at least 5 marathons under their belt. Not surprisingly, they found that the marathon runners' Framingham risk score (7%) was significantly lower than the score in a group of healthy age-matched controls (11%). Marathon runners experienced a 52% higher HDL cholesterol level, an 18% lower LDL cholesterol level, a 15% lower body mass index, and a 12% lower systolic blood pressure as well as a significantly lower resting heart rate (65 bpm vs 76 bpm). Coronary artery calcification (CAC) score was similar in marathon runners and age-matched men; however, when CAC scores were compared for marathon runners and age-matched men with a similar low Framingham risk score, then 36% of marathon runners were found to have a CAC score of 100 or higher as compared to only 22% in the control group.

MRI studies of the marathon runners indicated that 12% had late gadolinium enhancement (LGE), a marker of cardiovascular damage. Overall, LGE was associated with high CAC scores and an increased number of completed marathons. During a mean follow-up of 21 months, 4 coronary events occurred among the runners, 2 of which required resuscitation.

The researchers conclude that marathon running does not seem to protect against atherosclerosis as indicated by a high CAC score and may, in fact, exacerbate the problem due to excessive vascular oxidative stress, and frequent bursts of inflammatory cytokines experienced during long-distance running. The authors conclude that, "Regular marathon running has a beneficial effect on the cardiovascular risk factor profile but the extent of calcified coronary plaque is underestimated from that risk factor profile, with 36% of marathon runners aged 50 years or greater having a CAC score of 100 or greater and 9% of these requiring coronary revascularization during two years of follow-up. Advanced CAC scores seem to contribute to increased myocardial damage and appear to impair outcome. Frequent marathon running may not protect these athletes from the risk of coronary events."

Mohlenkamp, S, et al. Running: the risk of coronary events. European Heart Journal, Vol. 29, 2008, pp. 1903-10
Schmermund, A, et al. The risk of marathon runners – live it up, run fast, die young? European Heart Journal, Vol. 29, 2008, pp. 1800-02 (editorial)

Editor's comment: This study adds to the evidence that exercise in moderation is good, while vigorous exercise taken to extremes may produce unhealthy stress on the cardiovascular system.