Run to Your Heart’s Content: Marathons Not Linked With Subclinical Atherosclerosis

Long-distance runners with multiple marathons under their belts may have more aches and pains than the average person, but their arteries do not show any early signs of developing atherosclerosis, new research shows.

In a group of male adults with a history of running, including half marathons, full marathons, and even ultramarathons, researchers observed no signs of arterial stiffness or endothelial dysfunction. There was, however, a significant association between age and increasing intima-media thickness (IMT) and two measures of arterial stiffness: augmentation index (AI) and pulse wave velocity.

“Repeated marathon running per se does not pose an independent risk factor for the development of premature vascular dysfunction subsequently leading to atherosclerosis,” conclude lead investigator Axel Pressler, MD (Technische Universität Munich, Germany), and colleagues. “Instead, running multiple marathons appears safe from a vascular perspective in having a neutral effect on subclinical markers of vascular impairment.”

Carl ‘Chip’ Lavie, MD (John Ochsner Heart and Vascular Institute, New Orleans, LA), who was not involved in the study but who has studied the relationship between exercise volume and cardiac benefits, said the results are a “bit comforting” in light of previous studies suggesting that strenuous, high-volume endurance exercise might actually have deleterious effects on the heart. But he stressed the study does have important caveats, most importantly the age of the runners studied.

“A lot of people would consider 44 years old, the mean age in the study, to be relatively young,” said Lavie. “Maybe middle age would be 55 or 60 years old? But 44 is pretty young, and you wouldn’t really think a 44-year-old would have a lot of vascular disease. So, if you do measurements like IMT and other peripheral vascular assessments—which, granted, there have been small studies before showing [the measurements in marathoners] were abnormal compared to controls—you wouldn’t expect to see a lot of disease.”

Those caveats aside, Lavie said it’s nice to know that “doing a whole lot of marathon running in this age group doesn’t obviously or markedly worsen IMT and vascular stiffness.” 

J-Shaped Exercise Curve Postulated

In the paper, which was published June 7, 2017, in the European Journal of Preventive Cardiology, Pressler and colleagues point out there has been a debate as to whether strenuous exercise, such as marathon running, causes harm to the heart and vasculature. To TCTMD, Pressler said those concerns first emerged in the late 1980s over acute cardiac changes seen in some athletes, such as elevations in cardiac biomarkers, including troponin, after the completion of a marathon.

“This was the start of a debate over whether there might be a distance in running that would be too long or too much,” said Pressler. “There were also other studies showing, surprisingly, increases in coronary calcification. There was a landmark study in 2008 showing increased atherosclerosis development in the coronary arteries of marathon runners. You would have otherwise thought these would be healthy individuals, with less atherosclerosis than their age-matched counterparts.”

Additionally, studies have shown temporal impairments in right ventricular function in response to marathon running. With epidemiological data showing no survival benefit for individuals who exercise at high volumes and intensities, some have postulated a “J-shaped” curve, with moderate physical activity getting the biggest bang for the buck.   

Given this, the researchers sought to assess whether marathon participation in a group of seasoned male runners altered measures of arterial stiffness and endothelial function, which are subclinical markers of premature atherosclerosis. The study included 97 healthy men who recently completed the Munich marathon. The runners had previously completed a median of 8 half marathons, 6 full marathons, and 3 ultramarathons. They ran approximately 60 km (about 37 miles) per week as part of their training.

In assessing multiple parameters, which were measured before and after the subject’s participation in the Munich marathon, the “runners showed normal mean values for all vascular parameters with respect to established reference ranges,” according to the researchers. These included assessments of IMT, ankle-brachial index, pulse wave velocity, AI, and the reactive hyperemia index. The researchers did not observe any differences among runners who finished at least one ultramarathon and those who completed only one half- or full marathon prior to the Munich marathon.

Increased IMT, the presence of carotid plaque, or both, was seen in 12% of the runners, and while these individuals had run more races, they were also a decade older than the average age of participants.

Pressler said their study addressed at least one of the criticisms of previous studies, specifically the analysis showing a higher-than-expected burden of coronary calcification in marathon runners. That study included individuals who turned to running later in life, and some were previous smokers, so it was impossible to determine if these other factors affected the degree of coronary calcification. The current study, on the other hand, included a group of seasoned and healthy runners without any cardiovascular risk factors, he said. 

For Lavie, the conclusion that running multiple marathons is not a risk factor for developing atherosclerosis is a bit of an “overreach,” given that the manifestation of atherosclerosis is more prevalent in 50-, 60- and 70-year-olds and also given the lack of control arm in the paper. He said small studies have raised the issue that there are increases in coronary calcification among long-distance endurance athletes, and even shown evidence of plaque on IVUS, but such a finding is unlikely to be evident in a young cohort.

“I don’t think the study shows that marathon running or extreme exercise doesn’t cause atherosclerosis,” said Lavie. “Granted, though, there is no randomized data out there because all you can do is take a select group of marathons and compare them to a control group. Then, it’s how well are they matched? It’s always a challenge.”

Pressler conceded the lack of control arm in the study is a limitation. However, the reference ranges used as the comparator are based on large populations of healthy individuals similar in age to study participants. Regarding the age of patients, Pressler also agreed the study participants are middle-aged and it would be ideal to study individuals with longer exposures to endurance exercise.

One problem in performing a similar study in 60 and 70 year olds is the limited pool of participants. “We do see them in our outpatient clinic, but there’s not as many of them,” said Pressler. “And lots of them are also exposed to other risk factors, such as hypertension. To find a really healthy cohort in that age group is not so easy.”