Every so often, a scientific report about runners and heart disease really captures the attention of the media. About a week ago, a report in the March/April edition of Missouri Medicine entitled “Increased Coronary Artery Plaque Volume Among Male Marathon Runners” generated quite a bit of interest and discussion. I’ve written previously here at the blog about the general issue of the “heart healthiness” of long-distance running in a post entitled “Don’t Stop Running Yet!” I still feel that way. But let’s take a look, though, at this new article about marathoners and coronary plaque.
The report is written by a large group of very credible investigators from the Minneapolis Heart Institute, Integra Group, University of Colorado, Medtronic Inc., University of Minnesota, and the Mid America Heart Institute. Included in the group of authors is Kevin Harris, MD, who authored an important 2010 report on triathlon-related fatalities, William Roberts, the Runners World “Sports Doc” and medical director of the Twin Cities Marathon, and James O’Keefe, MD, a one-time triathlete who has been an outspoken critic in recent years of excess exercise.
The investigators report on a group of 50 male participants in the Twin Cities Marathon who had run at least 1 marathon per year for 25 years in a row. The average age was 59 years. None of these subjects had any history of heart disease or any current symptoms suggestive of heart disease. The runners underwent testing that included measurement of the height and weight, blood pressure, and resting heart rate; a 12-lead EKG; and blood tests for serum lipids and creatinine. The subjects also completed a questionnaire about historical lifestyle and risk factors. Each of the athletes underwent a high-resolution coronary computed tomographic angiography (CCTA) study. A control group of 23 sedentary men were identified from a contemporaneous group who were undergoing a CCTA study for some clinically-necessary reason and also underwent the other tests just like the runners did. The subjects and controls were similar in terms of: age, resting blood pressure, height, smoking history, serum creatinine, total cholesterol, and low density lipoprotein (LDL) levels.
Coronary artery plaque “lesions” were identified in both the runners and the controls: 95 lesions in 30 of the 50 runners, and 46 lesions in 12 of the 23 controls. The total volume of plaque was greater among the runners and this was also true for the amount of calcified or non-calcified plaque, as well. There was no difference in the lesion area, lesion diameter, or lesion length between the runners and controls.
Why is this all important? Because coronary plaque is generally associated with problems like heart attack. In clinical practice, we ordinarily discover coronary plaque when we search for a cause of a patient’s heart attack. Or, in recent years, we discover the plaque when an individual undergoes a screening test like a coronary calcium scoring CT scan. And we know from studies of individuals (not necessarily runners) who’ve undergone coronary calcium scoring CT scans that those with high calcium scores, indicating plaques, there is a greater risk of future heart attack. So it’s somewhat surprising that seemingly healthy long-time runners would have more coronary plaque than the sedentary controls.
On the bright side, despite being nearly 5 years older on average than the controls, the runners had significantly lower resting heart rate, weight, and body-mass index (BMI), less hypertension (high blood pressure), less diabetes, and an increased level of high density lipoprotein (HDL), the “good” cholesterol.
All of this news isn’t really new, though. These investigators first reported their findings at the 2011 meeting of the American Heart Association. It’s just now making its way into print, and into a rather unlikely and somewhat obscure medical journal for some reason. Missouri Medicine, the journal of the Missouri State Medical Association, even sent out a press release with advance copies of the article and accompanying editorials to a wide distribution list, all to take advantage of the lead-up to this year’s Boston Marathon. All pretty sensational, really. I can’t recall anything quite like this for research that was already more than 2 years old.
Given their findings, the authors conclude that “chronic excessive high intensity exercise” is the cause for the plaque build-up in the runners. They hypothesize that the mechanism is related to metabolic or mechanical stresses placed on the heart and coronary arteries during running that may be mediated by inflammation. The authors suggest, then, that “some runners” ought to “choose shorter, less exhausting challenges” in order to avoid this problem. On the face of it, this is a neat narrative, but….
1. Although the plaque volume (the total amount of plaque) was greater in the runners than the controls, the percentage of affected individuals in the running and control groups was not significantly different. Remember that 30 out of 50 (60%) runners had plaque identified and so did 12 out of 23 (52.2%) controls. In the statistical sense, those percentages are not significantly different. In terms of the most obvious, and perhaps most important, endpoint–the number of affected individuals with coronary plaque, the prevalence of coronary plaque–the study is essentially a negative study. Negative studies are hard to get published and I suspect this is why this report was published 2+ years after the study was completed.
2. If running was the cause of the plaque build-up, then why did only 60% of the long-time runners have this problem? And why did 52.2% of the controls have this problem, assuming that they were truly sedentary? Obviously the “cause” of plaque build-up in the coronary arteries is multifactorial. The authors can’t have it both ways: running cannot be responsible in the runners yet not responsible in the controls. For the runners, the real question is: what unmeasured variables might account for the finding of coronary plaque. We simply don’t know.
3. What is the consequence of having asymptomatic coronary plaque in a long-time runner? We don’t know. The current study doesn’t address this issue and to my knowledge, no study has. I’ve certainly heard from long-time endurance athletes who’ve been found to have coronary plaque, or elevated score on a coronary calcium scoring CT scan, who ask about the significance of the finding. We obviously need studies to find out what happens to such athletes.
4. What about….other endurance sports? And women? And younger athletes? There are just many, many questions left to be answered.
So, what’s the runner to do? I would still suggest that you not stop running. There’s every reason to believe that exercise is a healthy pursuit and there’s every reason to believe that exercise leads to better longevity, even for long-time endurance athletes. But stay informed. The general issue about the possibility of too much exercise is receiving a lot of attention. More studies are sure to come. And little by little, we’ll piece together the information that will help us determine if there is some sort of “sweet spot” in terms of the amount of exercise that is most heart-healthy.
Two articles on this topic caught my eye this week. Both are good reading. Amby Burfoot, the long-time editor at Running World and winner of the 1968 Boston Marathon, wrote an online piece for his magazine entitled “Heart Risk? Marathoners Have Increased Artery Plaque.” Interestingly, Amby learned last spring that he falls into the category of long-time runners with an (asymptomatic) high coronary calcium score. The second article was by Kevin Helliker in the Wall Street Journal, entitled “Why Runners Can’t Eat Whatever They Want.”