Thursday, 8 May 2014

Sigh. Is marathon running bad for your blah blah blah

I had originally decided that I couldn't be arsed posting this, but I saw a recent post in Outside magazine titled The Runner's Ticking Time: Why Runner's Need to Pay More Attention to Their Hearts which got my ire up again. Ignoring for a start the fact that one of the expert opinions that they quote is a registered dietician "who appears regularly on Good Morning America" (although at least dieticians are actually accredited, unlike nutritionists), the article is about the apparently high levels of heart attacks due to coronary artery disease that are seen in marathon runners. They even quote a paper from the Journal of the American College of Cardiology which says that "one in 50,000 will experience a heart attack from coronary artery disease during a marathon". Scary. Except that they miss out the kind of crucial (I think anyway) point that this is an incredibly small risk as compared to that of the general population. Here is the conclusion from the abstract in full:
Although highly trained athletes such as marathon runners may harbor underlying and potentially lethal cardiovascular disease, the risk for sudden cardiac death associated with such intense physical effort was exceedingly small (1 in 50,000) and as little as 1/100th of the annual overall risk associated with living, either with or without heart disease. The low risk for sudden death identified in long-distance runners from the general population suggests that routine screening for cardiovascular disease in such athletic populations may not be justifiable.

Now this is actually quite an old paper from 1996, but the overall conclusions seem pretty much the same as every other such paper that I have seen; occasionally runners die from sudden cardiac problems, which is of course terrible, but in general if you compare the mortality rates between runners and non-runners it seems that running is incredibly beneficial to your risk of dying. And that is just looking at cardiac problems, never mind other diseases. However, then we have the various studies coming out suggesting that we shouldn't run because it is bad for our hearts and can cause severe cardiac problems. How can both of these be true? 

A few weeks ago I received an email from the editor of the journal Missouri Medicine telling me that an embargo had been lifted on a paper due to be published in the next edition titled "Increased Coronary Artery Plaque Volume Among Male Marathon Runners". Since the Wall Street Journal were running a story, they had lifted the embargo that prevented anybody from releasing details of the paper until April 2nd. I was a little unsure why I was sent this email at first, but then I realised - it's this exact blog post that I am typing now. 

Now, I don't for one minute think that I have a particularly high number of readers (plus my Mum probably doesn't care), or that I am any kind of authority on, well, anything really. But in this world of TwitBook and instant communication, this is a very clear way of getting what is realistically a pilot study in a journal that nobody will have ever heard of (outside of the medical community in Missouri I guess) out into the world. The email will likely have been sent to every idiot with a running blog (hence why I got it). As I predicted, people have been discussing this paper for weeks and giving it far more merit than it would have otherwise garnered if not for social media and the fact that we runners like to have an opinion. This post has been sat in my drafts folder for weeks, and I almost didn't post it as I am basically feeding the fire here. But I figured it would at least be good to let other people see a different take on the results for this paper, plus I felt like it was time wasted if I didn't actually post the thing (where at least it's time wasted for both of us...).

Let me be clear up-front - I am not a subjective commentator here. As a runner, and particularly a runner who enjoys long distances, I have my own biases which will probably be pretty clear. I am (at least based on any easily observable measurements) much fitter than I was before I ran. And I was no slouch back then, being a black belt in Tae Kwon Do and training most nights. Of course I then went drinking afterwards, and didn't exactly take great care with my diet. My weight is much better now, and my heart rate and blood pressure are too. So I see taking up running as being an incredibly positive step in my life. However, despite that, I like to think that I am able to see things in a relatively subjective way, and if I see a study that has merit I don't just dismiss it out of hand because I don't like the results.

So anyway, this paper. I'm going to try and keep this brief, because frankly I can't be bothered spending too much energy on it. The research has been conducted by Robert Schwartz, James O' Keefe and colleagues. Drs Schwartz and O' Keefe are two of the main proponents of the recent body of evidence suggesting that low levels of activity are better for you than high levels of activity. First of all, let me say something here - I don't really doubt this to a degree. Is running good for you; yes. Is trashing your entire body to crawl across a finish line 100 miles away "good" for you; I highly doubt it. But is it the act of running itself that is the problem? Or is it all of the other stuff that we do to ourselves to complete races - running despite suffering injuries, eating the wrong things, over-training, under-training, etc?

I've discussed some of the other studies that are supposed to show how running affects cardiac function. It seems to me that whilst these small studies have detected a potential correlation of running with markers that may be indicative of changes to heart function, it is in no way clear that it is a causal effect - i.e. that it is the running itself that has caused the problems. There are all sorts of confounding factors that are just as likely to be responsible (e.g. a lot of runners used to be pretty unhealthy and are trying to make up for it now). In fairness, the study that would need to be done to show a direct causal effect is nigh on impossible - take a bunch of people with normal cardiac function, randomly assign them into two groups, one group runs, the other doesn't, then you look at cardiac function in say 20 years time. And the authors point this out as a limitation of their research.

Another point that is brought up in these papers is that the copious benefits that you get from running eventually plateau (again, no argument from me here), but somehow this is extrapolated to indicate that running further somehow makes things worseHere is a figure, taken from the paper "Minimum amount of physical activity for reduced mortality and extended life expectancy: a prospective cohort study" in the Lancet, which is used to show how vigorous exercise is "worse" for longevity than moderate exercise. Except it clearly shows that it reduces all-cause mortality by about 45% with 50 minutes a day. Now okay, you don't see any more benefits if you keep going further (no shit - so running all day won't make me immortal?!), but running for longer doesn't actually make this line go down does it? This particular misinterpretation particularly annoys me, as it is one of the central tenets for James O' Keefe's preaching of running "at a comfortable pace and not too far" and yet just does not stand up to scrutiny.

In this most recent research, 50 individuals were selected based on their having run at least one marathon per year for the previous 25 years. Various aspects of their health were measured, along with a quantitative assessment of the level of plaque build up in their coronary arteries using high resolution coronary computed tomographic angiography (CCTA; essentially uses a CT scanner to look at the inside of blood vessels). The measurements were then compared to a group of 23 individuals selected from a panel of people who had undergone CCTA and had self-identified as living a sedentary lifestyle.

The 23 control subjects were selected in order to match various aspects of the runners' health as closely as possible, but despite this it was impossible to match for certain things which it seems are simply far improved in runners compared to non-runners. So the runner cohort showed significant improvement in many health factors, including lower heart rate, lower levels of HDL cholesterol, lower weight, and lower cases of hypertension, hyperlipidemia, and diabetes. All sounding pretty positive on the running side so far considering that this control cohort was selected specifically to match the runners as closely as possible.

The real crux of the paper comes in the fact that there seems to be an increase in the levels of cardiac lesions and plaques in the marathon runners compared to the non-runners. Calcified plaques are at risk of breaking away from the lesion and causing a block in the arteries. The worry then is that if marathon training is causing our hearts to become more damaged, this could lead to an increased risk of suffering from catastrophic cardiac issues. If this is true, then it is definitely something that we should be aware of, and examples such as the deaths of ultra marathon runner Micah True, and runners in various marathons over the past few years are used to show the prevalence of heart problems in long-distance runners. As they say in the paper:
"A recent study found the incidence of sudden death in marathon running is approximately 1 in 100,000 participants, with coronary artery disease (CAD) accounting for the majority of fatalities. Fortunately, these deaths, though tragic and disturbing, are rare."
So the risk of CAD in marathon runners is less than 1 in 100,000 according to a recent study? This is even lower than the 1 in 50,000 risk that was specified in the 1996 paper mentioned at the start of this post (granted that was a while ago now...), and the conclusion was that this was miles smaller than the risk for the general public, and therefore not something that we should worry about.

But the big difference between runners and non-runners is not that more runners show these plaques, as the prevalence of plaques was pretty much the same between both groups (52% in the non-runners vs. 60% in the runners group, which is not statistically significant in their analysis). The difference is instead in the size of the plaques, and in particular in the volume of calcified plaque (which may be more likely to break away from the lesion and cause issues), which is significantly higher in runners. This is actually a pretty interesting, and largely unexpected result. Granted this is only a small sample size, but the difference is indeed quite stark. 

So tying this in to the work from AndrĂ© La Gerche that showed that extreme exercise can cause right-ventricular dysfunction (read me moaning about this paper here), the theory is that marathon running (and beyond) causes increased stress on the heart, resulting in increased cardiac plaque volume. Importantly, we don't see more people with plaques - just bigger plaques in those that have them. So this suggests to me that it is people with a pre-existing condition that are likely to be affected. But all of this is kind of moot isn't it, as we already know that we do not see more heart attacks in runners compared to non-runners. 

So here is what I take from all of this:

  1. Running improves many, many factors associated with health
  2. But runners can still suffer from cardiac problems 
  3. Running may aggravate pre-existing cardiac problems (although a direct causal link is not proven)
  4. But regardless, runners still suffer fewer fatal cardiac problems than non-runners

It's not that I don't believe that running marathons can aggravate heart conditions. It's just that the whole way that this has been presented seems a little over-the top to me. It is released in a special edition of the journal titled "Marathons In the Long Run Not Heart Healthy", and include additional articles from other cardiologists bringing up lots of tired arguments like the death of Jim Fix and Pheidippides - whose last words were definitely "my feet are killing me!". Definitely. It is represented in a way that suggests that this is an authoritative paradigm shifting theory, despite the overwhelming evidence that your chances of suffering a heart attack are drastically reduced by running marathons. It is at best a mildly interesting correlation, but of course has been eaten up by the media.

So here's the kicker; Is running healthy? Yes. But do I need to run so far to see those health benefits? No, probably not. I could train to be a 10K runner and probably still be just as healthy. But I love long-distance running, the places it takes me, and the wonderful people I meet along the way. Do I run for my health? No, it is just a nice additional benefit. But it is obviously a very good idea to stay on top of your health. Many cardiac problems have a large genetic factor to them, so if there is a history of cardiac problems in your family, get yourself checked out. Forearmed is forewarned and all that. But otherwise don't let the hyperbole in the media get to you (as I'm sure you probably don't anyway). Right, enough of that, I'm off out for a run.

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