Posted by Dave on June 27, 2011 | 12 Comments
Sure, marathons are enjoying a tremendous rise in popularity, as the above video from the 2010 New York Marathon illustrates vividly, but is it possible that running too many marathons can be harmful to your health? This is the second of a pair of posts on the issue.
On Friday, I discussed a 2009 report by Frank Breuckmann et al. which suggested that there might be a connection between a heart defect and extreme exercise. There were several problems with the research, most importantly that the results weren’t statistically significant.
This year a new study has been conducted using similar methods: Take MRI images of the hearts of marathon runners, and compare them to non-marathoners. In this case, there was a twist. Instead of just picking any old marathon runners, the researchers limited their sample to runners over age 50, with a lifelong history of training. Many were recruited from a club that limits its membership to runners having completed over 100 marathons. These runners, all men, were compared to younger athletes who train at similar levels, as well as men their age who had never completed a marathon. None of the participants in the study, led by Mathew Wilson, had heart disease or a family history predisposing them to heart disease, and unlike in the Breuckmann study, only one of the marathoners was a former smoker (and this person didn’t have evidence of heart disease).
The question: Does more-intense training and competition correlate to even more heart problems than moderate training?
Wilson’s group averaged completing 178 marathons, compared to Breuckmann’s requirement of only 5, so obviously Wilson’s group is a much more extreme group of runners. The initial findings of Wilson’s team were startling. Half of the 12 runners they examined exhibited the Late Gadolinium Enhancement (LGE) that had concerned Breuckmann’s team. As I mentioned Friday, LGE can be associated with heart disease, and if half the runners they studied show this defect, that is indeed troubling. Unlike the Breuckmann research, the Wilson results are statistically significant for marathoners compared both to the young athletes and the same-age non-athletes: No members of either of the other groups had any LGE.
Despite the very small number of runners tested, the results are statistically significant, and this is indeed troubling news for very active marathoners and ultrarunners. One very plausible explanation for the combined results of the Breukmann and Wilson studies is that running extreme endurance events can lead to heart disease, and running more of them makes heart disease more likely. We see a pattern of no heart disease in younger runners and in non-runners, with more evidence of disease as the level of running activity increases.
But still, this research doesn’t answer the most pernicious questions. Clearly moderate exercise is helpful, so what constitutes an “extreme” amount of exercise? Is the damage caused by the races themselves, or the high mileage logged in training? If training is the root of the problem, how much training is acceptable? Do marathoners have a higher rate of heart disease overall than non-marathoners? Remember, the participants in these studies were chosen because they had no risk factors and no previous evidence of heart disease. It could be that heart disease is even more prevalent among sedentary people than among marathoners: those individuals have been excluded from study.
What does this mean for you?
If you’re over 40 and a very active marathoner or ultrarunner (20+ races), it is almost certainly a good idea to get a thorough heart-health examination, especially if you have a family history or other indicators of heart disease. Unless you are very prolific, most likely you will be given a clean bill of health — even with 50% smokers, the Breukmann study found only about 1 in 10 marathoners with a potential problem — but it’s better to be aware of your health issues than to ignore them.
If, like nearly all runners, you don’t run dozens of marathons (or are a woman), it’s unclear how these results apply to you; we need more research to find out more about when a marathoning career becomes dangerous to your health. Almost certainly, a moderate (but not extreme) amount of running, even including some long races like marathons, is beneficial your health.