A complex picture on marathoning and heart disease

Posted by Dave on June 24, 2011 | 4 Comments

Jim Fixx (Source: BBC)

ResearchBlogging.orgJim Fixx was an overnight sensation as a recreational runner who had worked himself into shape and written a book about the health benefits of running. But when he died of a heart attack shortly after a run at age 43 52, he became the poster-child for the idea that running can actually be hazardous to your health. In fact, he probably didn’t die from running: his prior smoking and heavy drinking — and a family history of heart disease — were likely to blame for the incident, but the myth of Jim Fixx remains entrenched in the lore of running.

Even so, a quarter-century after Fixx’s death, the relationship between running and heart disease remains difficult to decipher. There is little doubt that moderate exercise paired with other healthy habits can do a lot to stave off heart disease and myriad other health problems. But what about extreme exercise? As hundreds of thousands of runners go beyond merely jogging and enter in ever-greater numbers into exhausting half-marathons, full marathons, and even ultramarathons, could this seemingly benign hobby actually be harmful?

I’ve been a runner all my life, but like many people my age (44), I’ve recently become much more intense runner, building over two years from 15 miles or so in a typical week up to nearly 70 some weeks. I’ve run my first two marathons, and I’m planning on running more. In my marathons, I’ve approached total exhaustion, unable to pull myself up from the ground after sitting down to rest in the finish area. Could this kind of abuse be detrimental to my long-term health?

I’m going to write a couple of posts on this topic, so I can’t give a full answer just yet, but I thought I’d start by discussing an intriguing 2009 study led by Frank Breuckmann. The team of German researchers recruited 102 male marathoners age 50 or older who had run at least five marathons. They matched them with a control group of non-runners with a similar age profile, who didn’t participate in endurance sports. Neither group had a history of heart disease.

LGE (indicated by arrow) is a significant predictor of heart disease

Each volunteer’s heart was scanned with a sophisticated MRI technique designed to detect abnormalities that put them at risk for heart disease. The researchers found that twelve runners and just four of the control group had late gadolinium enhancement, or LGE. Cardiac MRI involves injecting into the bloodstream liquids containing metals such as gadolinium that are detectable by a sensitive magnetometer. When a characteristic pattern — LGE — appears in blood vessels around the heart, previous research has shown a higher incidence of heart problems later.

However, in this case the LGE of only five of those runners was the type that predicts heart disease. This, it turns out, was not a statistically significant result. In other words, scientifically, we can’t say anything about the LGE levels in marathoners versus non-runners.

But the researchers also followed up with both groups for nearly two years to see if one group actually had more heart attacks and other “cardiac events.” Here, the results were significant: Three runners experienced cardiac events, compared to just one non-runner.

Does this mean that marathoning causes heart attacks? While the results of this study are shocking, it’s not reasonable to jump directly to that conclusion. One possible explanation for the non-significant but higher incidence of LGE in the runners is that running actually delays the onset of heart disease. Remember, people who’ve had heart attacks were excluded from the study; it could be that in the control population, men who were likely to have heart attacks would have already had them. In this scenario, being a marathoner, far from hurting you, can actually help defer heart attacks. It’s also possible that while running is generally beneficial, it might be harmful in cases where there are other indicators of heart disease like smoking or a family history. Indeed, over 50 percent of the marathoners in the study were former smokers, so that could have had a big influence on the results.

What does this mean for you?
If you’re a man over 40 and you have other risk factors for heart disease, this study suggests you might want to get a thorough heart-health evaluation if you run or plan to run significant distances (like marathons, or heavy training upwards of 40 miles a week). Of course, if you’re already at risk for heart disease, this sort of evaluation wouldn’t be a bad idea in any case. If you run less than that, this research probably doesn’t apply to you at all, and other research suggests moderate exercise almost certainly is good for you. Either way, the study is too small to show a genuine risk from marathon running. This study on its own isn’t enough to make the claim that people shouldn’t be running marathons—and of course it doesn’t apply to women at all!

Breuckmann, F., et al. (2009). Myocardial Late Gadolinium Enhancement: Prevalence, Pattern, and Prognostic Relevance in Marathon Runners. Radiology, 251 (1), 50-57 DOI: 10.1148/radiol.2511081118

Comments

4 Responses to “A complex picture on marathoning and heart disease”

  1. Travis
    June 24th, 2011 @ 5:45 pm

    In my marathons, I’ve approached total exhaustion, unable to pull myself up from the ground after sitting down to rest in the finish area.

    Two anecdotes about my first marathon in 2006.

    1. After the race my quads were so dead that I couldn’t stand up after using the porta-potty. The walls were smooth plastic, so there was nothing to grab onto to pull myself up. Eventually I managed to pull/push myself off the seat, and then tried to avoid sitting for the rest of the day unless I had something/someone to help me get back up.

    2. I had a fairly substantial amount of chafing (aka chub rub) on the insides of my thighs, where my legs had been rubbing together during the race. The chafing was pretty bad, to the point that it was basically a friction burn. I didn’t think much of it after the race – it wasn’t uncommon for me to have some chub rub after a race or long run, although this was worse than usual given the length of the race.

    Much to my chagrin, during my sleep that night the chafed spots on my legs fused together, and when I woke up my legs were attached about 10 inches about my knee. I don’t think I’ve ever had a less pleasant sensation than ripping apart my legs (and the newly formed skin) first thing in the morning.

  2. Piet Barber
    June 30th, 2011 @ 7:13 pm

    Jim Fixx was 52, not 43.
    (April 23, 1932–July 20, 1984)

    http://www.halhigdon.com/Articles/Fixx.htm

  3. Dave
    June 30th, 2011 @ 9:17 pm

    Thanks, Piet — fixed.

  4. Brendan
    July 1st, 2011 @ 7:39 pm

    I read this with great interest — about 8 months age, three days short of my 50th birthday, I went into cardiac arrest during a trail race. I had no risk factors for heart disease other than being over 40. Fortunately, a short distance behind me in the race were a cardiac nurse and a physician’s assistant, who kept me alive until the ambulance arrived. My cardiologist has OK’d me for running, but advises me not to try to win any races just yet.