More on marathoning and heart disease

Posted by Dave on June 27, 2011 | 13 Comments

ResearchBlogging.orgSure, 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.

Wilson M, et al. (2011). Diverse patterns of myocardial fibrosis in lifelong, veteran endurance athletes. Journal of applied physiology (Bethesda, Md. : 1985), 110 (6), 1622-6 PMID: 21330616

Comments

13 Responses to “More on marathoning and heart disease”

  1. mgeek
    June 28th, 2011 @ 2:49 pm

    “Many were recruited from a club that limits its membership to runners having completed over 100 marathons.” – wow! difficult to extend results to a “normal” population though :-)

    Am I wrong or annual medical evaluation with basal and exercise ECG is mandatory for every athlete only in Israel and Italy? I hope you can discuss this point in a future blog post.

    This March I wrote a small blog post on Italy planning to mass ECG screen teenagers: http://tinyurl.com/5urvocx

  2. Dave
    June 28th, 2011 @ 3:00 pm

    Thanks for the comment and link, mgeek. You’re right, the results are very difficult to extend to a normal population, but the pattern between Breukmann (5+ marathons, small effect) and Wilson (178 marathons, large effect) is troubling. I’m not sure if the ECG scan you mention would have caught this pattern in the runners, though — the MRI is a much more sophisticated (and expensive) test.

  3. sethleon
    June 28th, 2011 @ 8:18 pm

    ‘but the pattern between Breukmann (5+ marathons, small effect) and Wilson (178 marathons, large effect) is troubling.’

    If the Breukmann effect was not significant (and included smokers)I don’t see evidence for concern with marathoners who run a more reasonable # of races. Afterall the group with fewer races but similar training had no LGE in the Wilson study.

    Even elite marathoners race rarely (usually no more than two marathons in a year).

    Few would argue that racing a marathon is in itself healthy, but many would argue that proper consistent training along with occaisional tests of fitness gained (by war of racing) is quite healthy.

    Until type and extent of training along with number of races are included in a larger sample I don’t see cause to raise alarm for marathoners following a traditional training and racing model.

  4. Sam
    June 29th, 2011 @ 8:56 pm

    If this were a food that appeared to be harmless and you saw no effect in people that didn’t eat it, a small (not quite significant) effect in those who ate a bit of it, and a large and significant effect in people that ate a lot of it, I’m pretty sure that people (other commenters?) would be alarmed and probably avoid the food.

    There is no reason to treat this any differently, besides bias regarding things that seem like they should be healthy.

  5. Ultramarathoners at significantly increased risk of heart disease | The Coolest Thing I Learned Today
    June 30th, 2011 @ 3:26 am

    […] Wow..add that on to my list of excuses. […]

  6. Steve Shervais
    June 30th, 2011 @ 4:20 am

    Not being a marathoner (I have run after the garbage truck a couple of times), I don’t have an emotional attachment to this issue, but it seems to me we are one link short of a chain.

    So, we’ve demonstrated a statistical association between marathoning and LGE in highly trained people. And we’ve demonstrated a statistical association between LGE and heart disease in the general populace.

    One question that might be asked is, are the two populations equivalent as far as LGE is concerned? Another way of putting it might be to ask if the LGE for marathoners is the same as the LGE for everyone else — or is something happening to marathoners that shows up as LGE.

    One way to resolve the question is to look at the original LGE data and see if it can be stratified by level of training. Another way would be to follow the old marathoners from this most recent study around and see what their mortality rate is.

  7. gmak
    June 30th, 2011 @ 11:58 am

    This is based on the assumption that Late Gadolinium Enhancement (LGE) is part of heart disease or diminishes quality of life through health issues. I’m not sure that this has been conclusively proven (no?).

    Perhaps it is in the same category as when scientists said that lifting weight was harmful because they measured an increase in blood pressure in athletes lifting weights.

    Right data + assumptions can lead to wrong conclusions.

    Thoughts?

  8. Dave
    June 30th, 2011 @ 12:32 pm

    Good points, gmak and Steve. I’m not a doctor, but my sense is that LGE is a very strong predictor of heart disease. We’re not talking about a mild correlation, but rather a diagnostic tool that basically indicates that someone does have the disease.

    In the Breuckmann study, several of the runners with LGE had heart attacks within two years!

    Here’s a study showing how LGE is used to diagnose heart disease:

    http://content.onlinejacc.org/cgi/content/abstract/45/5/743

  9. N.E. Lilly
    June 30th, 2011 @ 2:48 pm

    The study says that the prevalence of LGE in veteran athletes was significantly associated with the number of years spent training. Isn’t that just correlation? Could there be other factors? Isn’t the traditional diet of Marathoners carb-heavy?

    I only ask because of the recent spate of information (mainly coming out of the Atkins/Paleo diet blogoshpere) blaming carb-heavy diets for heart disease.

    For example, a quote from “What if it’s all been a big fat lie” by Gary Taubes says, “Put simply, if the alternative hypothesis is right, then a low-fat diet is not by definition a healthy diet. In practice, such a diet cannot help being high in carbohydrates, and that can lead to obesity, and perhaps even heart disease.”

    (http://www.nytimes.com/2002/07/07/magazine/what-if-it-s-all-been-a-big-fat-lie.html)

    It’d be interesting to see the nutritional aspect of the athletes’ lives studied as well.

  10. sethleon
    July 1st, 2011 @ 11:33 pm

    My point was not that there is no cause for any concern. I think there is concern for those extreme outliers running on average 160+ marathons.

    I also think it is a mistake to equate those runners with the label ‘highly trained’. The majority of those running that many marathons from my experiance (anecdotal i concede) are not the fastest or fittest. I would also speculate these runners are not following traditional marathon training plans that call for long runs only 25-30 % of weekly training volume.

    There is abundant research stating the benefits of aerobic exercise and much of it show increasing benefit with increasing levels of exercise.

    I think it would be a shame if marathoners following consistant & balanced training plans were scared into reducing training loads based on research from subjects who likely followed training plans that may be quite different.

  11. sethleon
    July 1st, 2011 @ 11:47 pm

    Rather then seeing groups defined by ‘# of marathons run’ I think much better research would use categories based on training volume and consistancy (along with # of marathons).

    To be fit for a given marathon requires significant recovery from the prior marathon and then a period of rebuilding. So I would expect someone running monthly marathons to be less than ideally prepared. Combine less than ideal preparation with the stress of a marathon itself and then put that on a repeat cycle – probably not a great idea.

  12. GR Lap
    October 1st, 2012 @ 9:19 am

    I would rather run my two marathons per year – I completed #25 yesterday, Berlin (!) – and suffer the consequences, if any, than not run.

  13. Philip Knopp
    May 31st, 2014 @ 2:57 pm

    As a person with a Statistics background, I will suggest that the author do some research of his own based on the hypothesis he arrived at after reading two other studies. If is very difficult go do any analysis with a skewed sample of only 5 people that would be representative of the population he is interested in. Further study is needed.