Masters Athletes at Low Risk for CAD Seem to Develop Atherosclerosis Differently, Study Suggests

Most masters athletes who have engaged in endurance sports for years have normal arteries, a new study reassures. But for men, this level of exercise also is accompanied by an increase not only in the number of plaques but in the level of calcium in their arteries. Women show no such differences.

This is not entirely bad news, because this calcification may in fact be protective, senior author Sanjay Sharma, MD (St. George’s University Hospital, London, England), told TCTMD.

“Although marathon runners [and other masters athletes] have more calcium in their arteries, the plaques that they get seem to be much, much more stable than the plaques that normal people get, and this may actually protect them [against MI],” Sharma said. “[It] may explain why so few marathon runners actually suffer a cardiac arrest and why people who exercise all their lives live longer than people who don’t exercise.”

By focusing on individuals at low risk for CAD, the study is unique in that it was able to avoid some of the confounders that had bedeviled earlier research, Sharma explained. Other reports have shown more calcium in athletes’ arteries and more scar tissue in their hearts, he said, but these were confounded by enrolling subjects who had established risk factors for CAD like high blood pressure, diabetes, or smoking. In this study, by contrast, masters athletes had a mean Framingham Risk score of 3.4%.

Jonathan Kim, MD (Emory University, Atlanta, GA), who did not take part in the research, agreed that the low-risk population is the reason why this study “moves the needle” beyond earlier reports on the effects of endurance exercise. That the majority of subjects didn’t show any signs of atherosclerosis is a “huge” finding, he said in an interview, and is “really important for sports cardiologists like myself, because we see a lot of endurance . . . athletes and they read these data and they’re concerned.”

More Plaques, More Calcium

For their research published online last week in Circulation, Sharma along with lead author Ahmed Merghani, MRCP (St. Georges, University of London), and colleagues recruited 152 masters athletes (70% men; mean age 54.4 years) from running and cycling clubs in the United Kingdom as well as by advertising in the magazine Athletics Weekly. These subjects were compared with 92 controls of similar age, sex, and Framingham Risk Score. Participants were evaluated using echocardiography, exercise stress testing, CT angiography, MRI with late gadolinium enhancement, and 24-hour Holter monitoring.

Athletes had a mean of 31 years’ endurance exercise behind them, and trained for a median of 7.7 hours per week. Controls exercised for a mean of 1.9 hours weekly.

Normal coronary artery calcium (CAC) scores were seen in most masters athletes (60%) and controls (63%).

Among men, the masters athletes had a higher prevalence atherosclerotic plaques (44.3% vs 22.2%; P= 0.009). None of the controls had a CAC score of 300 or higher, as compared with 11.3% of masters athletes. Additionally, luminal stenosis of at least 50% was only seen in the male athletes (7.5%). Among men, plaques found in masters athletes were predominately calcific (72.7%), whereas those found in controls were mainly of mixed morphology (61.5%). Among women, there were no differences between groups for either CAC or the number of plaques.

Yet there were signs that, even in the absence of disease, some of the male masters athletes had experienced an MI. Of the seven men with MRI findings suggestive of such an event, only three had stenosis of at least 50% in the corresponding artery.

For the male masters athletes, the number of years of training was the only independent predictor of having CAC > 70th percentile for age and/or stenosis ≥ 50% (OR 1.08; 95% CI 1.10-1.15).

A Word of Caution

Leslee Shaw, PhD (Emory University), asked to comment on the study by TCTMD, said readers should keep in mind “that the sample size is small and that causation cannot be established between training and the development of atherosclerosis.” There also are no details provided on family history, the type and intensity of exercise, degree of overtraining, and myocardial biomarkers, she noted via email.

Moreover, Shaw said, the idea of calcification being a good thing, by virtue of stabilizing plaque, is “speculative.” And she expressed doubt that the level of physical activity seen here would be enough to promote atherosclerosis. “But at the extreme ends of exercise, [overtraining] may act as stress (akin to the relationship between cardiovascular risk and psychological stress) to promote atherosclerosis,” she suggested, noting that this is especially possible given the lengthy experience of these athletes.

Overtraining could be an issue, Kim agreed, adding that endurance athletes are “notorious for having bad training habits. [Some] train at all costs.” It may be that these individuals have unique risk factors, such as overtraining and poor diet, that differ from the traditional cardiovascular risk factors of more sedentary people, he added.

Calcium in your arteries means there’s been damage that has been repaired, Sharma observed. “You can damage your arteries by smoking, by high blood pressure, by having diabetes, and by having very high cholesterol levels. But clearly if you’re running 27 miles at one hit, 12 [or] 13 times a year, your heart does contract, the arteries must bend and flex, bend and flex, causing other forms of injury.” However, the mechanisms of repair in these two groups may not be the same. “When these plaques repair, that calcium is very hard and solid, not the sort of calcium that’s associated with atherosclerosis that we see in people with [traditional] risk factors,” he explained.

What to Tell the Athletes?

As to whether these findings should encourage or deter people from pursuing endurance sports, Sharma said: “I am very pro exercise, as all cardiologists should be. The benefits of exercise on the cardiovascular system are well established.

“We know that people who exercise reduce their risk of having a heart attack in their 50s and 60s by about 50%,” he continued. “They live anywhere between 3 and 7 years longer than people who don’t exercise. And outside of the cardiovascular system, exercise is antiaging, it’s an antidepressant, it’s an anticancer therapy. So it’s probably the most effective treatment that we could prescribe to any of our patients.”

Only 2.5 hours per week of moderate exercise are needed to reap these benefits and up to 10 or 11 hours weekly are known to be safe, he added. The question is what happens to people who have had high levels of exercise for many years. “There comes a point when you might start harming an otherwise normal heart,” Sharma said.

But concerns over plaque morphology shouldn’t enter into clinical practice at this point, he said. “We need much, much more information. We are in an era where human beings, the vast majority aren’t doing enough, but the ones that are doing too much are doing loads more than they used to do 20 years [ago]. So we need to keep our ears to the ground and keep tabs on these people,” he said.

Kim also said that, apart from the overall good news that most masters athletes are doing well, there is little here that should influence the cardiologists caring for them. For example, until more is understood about what’s driving the high calcium scores seen in some and whether that factor even relates to exercise, “you’re certainly not going to recommend calcium scans based on this study to every single male masters athlete that you take care of,” Kim emphasized, agreeing that “long-term, prospective outcomes data” are needed.

Importantly, he said, “We don’t know if just because these guys had absolute scores over 300, does that mean they’re having MIs sooner? Are they dying sooner?”

Sharma said the next step is to follow a larger number of subjects for a longer time frame, so that patterns can be teased out. This is particularly true for women, given that they might develop atherosclerosis later in life than their male counterparts, although the current study may have been underpowered to assess this group. “We need to do much, much more work in our female masters athletes,” Sharma stressed.