Years ago, exercise physiologists thought that anyone who could run a marathon would never have heart disease. They were wrong. Really wrong.
Legend has it that around the 6th century BCE, an Athenian messenger known as Philippides was dispatched to Sparta to ask for help when the Persians landed at Marathon, Greece.
Supposedly he ran 240 km (150 miles) in two days, then ran 42 km (26 miles) from the battlefield near Marathon to Athens to let the people know that the Greeks had been victorious.
After this big finale, he keeled over and expired.
Role model? Cautionary tale? We’ll get into that in today’s Research Review.
Does marathon running improve heart health?
I have to be up front about my bias: I really don’t like marathon running.
For years I’ve had been told that I should run, or at least do some sort of cardiovascular activity – and I do. But lately, anybody with any athletic talent (or not) seems to be running a marathon. Somehow, the media have latched on to the notion that marathoning is healthy.
Don’t get me wrong: For those of you who run marathons, I salute your dedication, perseverance and determination. However, I’m sorry, but it’s not healthy for you. Is it better than couch surfing? Well, yes — but so are a lot of things.
Now, I know that many other sports that aren’t too healthy either. It’s hard to argue, for instance, that boxing, rugby, or snowboarding are a quick route to wellness. In a sense, competing in any sport isn’t always compatible with health. Athletes have to push themselves beyond the normal range of human exertion, and they may have to do so in a context where there are projectiles, hard surfaces, hurty things, or other human beings flying at them.
The issue I have with marathon running, however, is the idea that running them on a regular basis is cardiovascularly good for you. Years ago, exercise physiologists thought that anyone who ran a marathon would never have a heart attack. They were wrong.
In this week’s review we’ve got a study looking at marathon runners and coronary atherosclerosis.
Möhlenkamp S, et al; Marathon Study Investigators; Heinz Nixdorf Recall Study Investigators. Running: the risk of coronary events : Prevalence and prognostic relevance of coronary atherosclerosis in marathon runners. Eur Heart J. 2008 Aug;29(15):1903-10.
Participants in the study were marathon runners over the age of 50 who ran at least 5 marathons in the last 3 years (5 x 42.195 km or 210.975 km). Participants were matched to control participants who were non-runners. The non-runners was matched to the runners’ age, BMI, smoking status and Framingham risk per 10 years.
Here’s a quick note about “Framingham risk”:
Framingham risk (which refers to the famous Framingham study of cardiovascular disease risk) is a calculation that estimates your risk of “hard” coronary heart disease outcomes (myocardial infarction and coronary death).
It includes gender, age, total cholesterol levels, HDL cholesterol levels, smoking status, systolic blood pressure (the first number & hopefully smaller) and in you’re on blood pressure medication. No questions on family history or activity level though.
If you’re interested in calculating your Framingham risk, go to the National Cholesterol Education Program website and use their online calculator. Good to know I have less than 1 percent risk of a heart attack.
Anyway, back to the study. All participants were screened to eliminate those with a history of heart disease and various other chronic diseases (diabetes, angina, renal failure and musculoskeletal disease). After screening, the study had 108 male runners between the ages of 50-72 years old.
On average these runners completed 20 marathons, started running marathons 9 years earlier, and trained 55 km (about 35 miles) five days a week year round. That’s a lot of running: 14300 km/year and 128 700 km over the 9 years of training.
There were 864 age matched controls and of those, 216 were matched for age and risk factors (except for Framingham risk – more on that later).
Risk factors and matching
If you want to figure out if marathon running affects cardiovascular risk, ideally you want to match all the risk factors and only have marathon running as the difference between groups. Unfortunately, of course, that’s impossible.
Even with 864 age-matched controls and only a handful of risk factors to match, they couldn’t get perfect matches. Instead the researchers settled for matches with everything, but – and this is a pretty big but – the Framingham risk.
What to do? Belt and suspenders — have two matching control groups! One group to match everything but the Framingham risk and a second group that matched the Framingham risk. Unfortunately, while they did the best they could, the researchers didn’t get a match control. Even with a fairly simplified risk calculator for cardiovascular risk, you still have several inputs. The researchers couldn’t find anybody who had matching risk, so no matches.
I do sympathize with the researchers — it’s pretty darn hard to find two people of the same age and exactly the same cardiovascular risk factors, who differ only in marathon running. In addition, finding matches would make the study easier, but then everything we know about the benefits of exercise (e.g. a better blood lipid profile) would be questionable.
Some fancy schmancy and really expensive equipment testing
Researchers used a C-150 electron-beam computed tomography, a cardiac magnetic resonance imaging device, and a Cuisinart (kidding; just checking to see if you’re paying attention). For those of you who watched ER you may know these as a CAT scan (or CT) and an MRI.
Coronary artery calcification
What were they looking for? CAC – coronary artery calcification. This is a buildup of calcium in your arteries.
Calcium in the coronary arteries is correlated with arterial plaque. Patients who died of coronary artery disease were found to have 2-5 times as much calcium as those who died of other causes. Now it seems we need to worry about both fatty plaques and calcium gunking up our arteries.
As your blood rushes past your artery walls, it does a little damage. If the arterial walls don’t heal themselves in a quick, robust way, this can lead to calcium deposits, which narrow the arteries. Researchers have also suggested that the physical properties of the calcium deposits themselves might weaken arterial walls or inflame the arterial plaques. As one study explains:
“[T]he presence of a soft plaque, with a point of weakness induced by inflammation adjacent to an area of calcification, predisposes the plaque to rupture because of the presence of a tissue interface of differing physical properties that is subjected to the pulsatile changes of arterial pressure.”
In other words, “building” arteries out of different, inconsistent materials, might cause part of the problem. It’d be the same as building a house out of a jumble of bricks, plywood, and plastic tarps: You’ll find some serious weak spots every time the wind blows.
Running makes the blood go faster and more often past the wall. In theory, this might mean there are more opportunities for damage. After all, if our jumbled house is built in a windy place, that’s a recipe for trouble. Hmm…the theory that people had a limited number of heart beats and should ration them seems to have a itty bitty tiny bit of scientific support.
The big finding is that 36% of the marathon runners have a CAC score of more than 100 (the score ranges from 0-400) and 9% of them had to have coronary bypass – within the 24 month follow-up. Actually, one of the runners had to be resuscitated after 7 km in a 10 km race. (Ouch.)
No differences between the age matched group and the runners, but the marathon runners had higher CAC scores than the Framingham matched group. Note: CAC scores were calculated from the CT and MRI imaging results.
This is a pretty straightforward study with a pretty straightforward conclusion:
- Men over 50 who run marathons regularly have higher levels of CAC (a known risk factor for cardiovascular disease) than age-matched controls
- In some cases the calcium blockage is so severe in 50-plus marathon runners, it requires coronary bypass surgery.
This study found that compared to controls, regular marathon running can increase the risk of a very specific type of atherosclerosis (artery hardening). Thus, marathon running doesn’t seem to be cardioprotective in this group.
Whether this is true for women or older/younger runners remains to be seen. We also don’t know at what point the health benefits of running, well, run out. How far can one safely run per week? One thing’s for sure: it’s not 55 km.
Running: good. Too much running: bad.
Run marathons if you enjoy them, if you find them a challenge, if they help you relax, if you find the rhythmic foot-pounding soothing, and/or for whatever other reasons you may have – except your cardiovascular health.
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