Exercise is one of the tenets of preventive cardiology, but concerns have been raised that extremely high amounts of physical activity can lead to coronary artery calcification, which itself is a risk factor for cardiovascular disease.
A new study of mostly middle-aged men in JAMA Cardiology found the most avid exercisers—averaging eight hours per week of vigorous exercise—did indeed show greater levels of coronary artery calcium (CAC). Nevertheless, they were less prone to dying over the average follow-up period of 10.4 years compared to men who exercised less, suggesting they can safely continue their workout regimens.
“The most important take-home message for the exercising public is that high volumes of exercise are safe,” senior author Benjamin D. Levine, MD, a sports cardiologist with University of Texas Southwestern Medical Center, said in a press release. “The benefits of exercise far outweigh the minor risk of having a little more coronary calcium.”
Levine and colleagues studied 21,758 men with varying levels of activity, categorized into three groups by multiplying their self-reported frequency and duration of exercise with the expected metabolic equivalent of task (MET) values for their specific activities. Participants were an average of 51.7 years old at baseline with no prior history of CVD.
Individuals who exercised most intensely were 11 percent more likely to have a CAC score above 100 compared to the other groups. However, avid exercisers with CAC above 100 weren’t any more likely to die over the decade of follow-up (hazard ratio: 0.77) compared to those with the lowest volumes of exercise. For those with CAC scores below 100, the most physically active group had about half the death risk compared to the least active group.
Although CAC in general has been linked to higher mortality—and now has an expanded role in the U.S. cholesterol guidelines—these findings suggest maintaining high levels of physical activity don’t accelerate the dangers of having CAC, even when calcification is already present.
“One may speculate whether there are similarities with high-intensity statin therapy, because high-intensity physical activity and exercise may promote more calcific atherosclerosis, which may be more stable than soft, noncalcified plaques, potentially leading to coronary stability and lower propensity to more morbid CVD events,” Carl J. Lavie, MD, with the University of Queensland School of Medicine, and co-authors wrote in a related editorial.
“In addition, those with high levels of exercise may have otherwise better CVD risk profiles and, therefore, lower coronary risk, and high levels of exercise could promote coronary collateral flow and increased coronary flow reserve that could also reduce the risk of morbid events.”
The editorialists said they would still recommend clinicians consider CAC testing in high-volume exercises with intermediate coronary risk profiles and use those CAC scores to determine which patients might benefit from more intensive therapies or exercise testing to investigate possible arrhythmias or ischemia.
Levine et al. noted their study was limited by its inclusion of only men, most of whom were white, educated and had good access to healthcare. There were also relatively few deaths (759 total), particularly among those with the highest levels of physical activity (40), which limited the statistical power of the analyses.
But the low death rates could also be seen as a good sign for workout junkies.
“In virtually every analysis, at any cut point of CAC or when considered continuously, individuals with the highest levels of physical activity had lower mortality than those with the lowest activity levels,” Levine and colleagues wrote. “These results do not support the contention that high-volume endurance activity, with a mean of more than one hour of activity per day, increases the risk of all-cause or CVD mortality, regardless of CAC level.”