Tuesday, December 17, 2013

So I want to run a marathon: Is my heart going to stop?

I mentioned a while back that the marathon bug has taken a big bite out of me. I'm not in love with the long training runs, nor with the way that my training brought some critics out of their closets, but I now regard the marathon as the ultimate challenge and the ultimate accomplishment.

I don't have any plans for a next marathon. I won't run one this spring, and I might not run one next fall. When the time is right, I will know.

But in thinking about the prospect of again putting my body through the grueling torture that is marathon training, I started to think about what scientists would say to me if they could give me some advice. Would they advise me not to do it at all? Would they advise me to keep up with it my whole life, maybe one per year? Is there any truth to the myth that long distance runners have healthier hearts and live longer?

So this is my new project. This is what my blog is going to be *about* for awhile. I will read the scientific journals and I will tell you what I learn.
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Fact or Fiction: Running long distances is bad for your heart.



We've all heard it at some time or another.

"Why are you running a marathon? Didn't the 
first marathoner drop dead when he finished?"

Yes, Pheidippides ran from Marathon to Athens to relay the message that the Greeks had defeated the Persians in the Battle at Marathon. Yes, he died after he made the announcement. At least, that's how the legend goes and that's the inspiration for the modern day marathon.

The real question is this: Am I going to drop dead like Pheidippides did?

Looking around, it seems that the odds are in your favor. Between 2000 and 2009, 3.7 million people crossed the finish line of a marathon, and only 28 people died during or within 24 hours of their finish. This guy has crunched those numbers.

Based on these statistics, it looks like Pheidippides was just a really unlucky dude. So when people try to diminish your marathon dreams with the Pheidippidean hammer, you can spit out those stats at them. Risk of death isn't a reason to refuse to lace up. There's hardly any risk at all.

So this brings me to a narrower question:

When people die during or after a marathon, is it the running that kills them?

According to this study which was published this year (2013), runners who have coronary atherosclerosis are most at risk of developing cardiovascular disease or, at the researchers put it, undergoing a "coronary event". Rather, I should say, people in general who have coronary atherosclerosis are most at risk. It is a condition of the coronary artery involving a thickening or hardening of the arterial walls. The calcification makes the opening of the artery ever narrower, which in turn increases blood pressure. It is important to note that it is people in general want to avoid atherosclerosis.

The researchers in this study found that "the coronary atherosclerosis burden helps to characterize the long-term coronary risk of recreational runners, with event rates comparable to our controls and findings from other population-based analyses."

In other words, runners and non-runners alike with coronary atherosclerosis are at the same risk of having a "coronary event".

However! They did find that marathoners who have run a lot of races have a higher rate of myocardial fibrosis--a condition in which heart tissue is replaced by a fibrous tissue, like scar tissue. "In the same cohort we reported that the number of completed marathon races was associated with a higher risk of myocardial fibrosis, which has been confirmed by others." That is, other people who were interpreting data collected from the same clinical study confirmed that there was a higher risk of myocardial fibrosis among the marathoners.

The problem is that the participants in this study self-select for the project by contacting the researchers. As the researchers themselves note, there might be a higher rate of myocardial fibrosis and coronary events among the runners they studied because those runners might already have been aware of their own heart issues and might be interested in having those issues monitored. A healthy runner (or one who is not aware of heart issues) might not be as likely to participate.

The researchers thus conclude that:

"The acute risk of recreational marathon running seems to be low and is probably not higher than that associated with any other physical activity."

Indeed, Tim Noakes wrote a response to the journal article: "Time to quit that marathon running? Not quite yet!" You can imagine his take on the whole thing.

Interestingly, however, another study that came out this year (2013) from a group of Canadian researchers found that marathons beat up the hearts of people who aren't very fit. "Completing a marathon leads to localized myocardial edema, diminished perfusion, and decreased function occurring more extensively in less trained and fit runners."

What does it mean to be "less trained and fit"? Well, it's a matter of putting in fewer miles and less time during training, and performing poorly (or relatively poorly) on fitness tests. The fitter you are, the better your heart will stand up to the 26.2.

The silver lining is that all this damage to the heart is "transient", meaning that it is not long-term. The researchers conclude that three months is the time needed for reversing the damage. ...Hey, if you were wondering how long it takes to recover...
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If all of this looks inconclusive, that's because it is. Long-term studies of marathoners are just now being conducted. It'll probably be another 10 years before we really know anything about what marathon training/running does to our tickers. Right now, it looks as though running does not increase your long-term risk of cardiovascular disease. And even though it can pose a "transient" increase risk, you can minimize that risk by increasing your overall fitness.

Basically, science is telling us that if we want to run marathons at all, we should go balls to the wall. 

That sounds about right.
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*I'm not a doctor or even a scientist, though I do work on Aristotelian science and epistemology. The only thing that makes me fit to serve up all this stuff is that I can read. You should read the studies yourself before drawing conclusions.

4 comments:

  1. I would make 2 comments:

    1. Studies on humans are freakin' ridiculous. Basically, this involves taking lots of people, asking them lots of questions, collecting lots of data, then trying to sort it out to see what kinds of things are correlated. This requires that: (a) people answer honestly; (b) scientists/doctors crunch data honestly; (c) no one is gaming for a really attention-grabbing headline; (d) readers are savvy enough to differentiate correlation and causation. *sigh* All of these factors SELDOM align. Reading (and conducting) studies like this is incredibly challenging. It's one reason that, although I love coaching, I would need to hear a very persuasive argument for why I should take on exercise-related research on people.

    2. Perhaps you're planning to go here - but the issues aren't only heart-related, although those are the attention-grabbing headline issues. But other questions - with much less immediate consequences - include the role that higher levels of free-radicals may cause in those who exercise, and both the short- and long-term metabolic effects of long stretches of sustained aerobic exercise. You've bitten off quite a lot here; and I'm excited to see where you take this topic. :)

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    1. Okay, I was eagerly awaiting a response from you. You are the true scientist, and I think it shows. You're already raising so many questions that hadn't occurred me.

      I want to lay out some preliminary discussion in a few areas, but then I want to come back around and look into some things more closely. This plan will make more sense when you see the other topics I'll bring in. The relationship between the heart and exercise probably gets the most attention, though, so I'll come back to that. Running and nutrition is also big, but I don't know how much I want to really delve into that.

      Reading through the little research that I did, I immediately got the impression that you express about the reasons for being skeptical about the data and the analysis. It's especially interesting when you get completely different interpretations of the same data.

      This totally never happens in philosophy. Ha.

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  2. I am pretty jazzed to live vicariously through your research... I love when people tell me that guy dropped dead. I tell them he probably didn't have water or gu.

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    1. That could be what his problem was! He needed a crew to hand him water. Or a CamelBak.

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