Why Some of the Fittest People on Earth Have High Coronary Calcium Scores
For years we have operated under a wonderfully simple equation: exercise equals cardiovascular health. And broadly speaking, that equation is still profoundly true. Move more, suffer less. Walk, hike, row, swim, cycle, climb mountains, carry heavy things uphill while questioning your life choices – your heart generally thanks you for it.
But medicine occasionally encounters paradoxes. Tiny biological plot twists that refuse to cooperate with our bumper-sticker understanding of physiology.
One of those paradoxes emerged when cardiologists began performing coronary calcium scans on older endurance athletes. These were not sedentary smokers living on gas-station burritos and existential regret. These were marathoners, cyclists, triathletes, and lean sixty-year-olds with resting heart rates in the 40s and enough mitochondria to power a medium-sized Scandinavian village.
And yet many of them showed surprisingly elevated coronary artery calcium (CAC) scores. Wait. What? The finding launched a fascinating debate in sports cardiology that continues today.
What Is a Coronary Calcium Score?
A coronary artery calcium scan measures calcified plaque in the coronary arteries. Higher scores generally correlate with higher cardiovascular risk. But CAC scoring does not directly measure unstable plaque, arterial inflammation, or actual blockage severity. Instead, calcium often reflects older, more stabilized plaque, almost like scar tissue within the arterial wall.
That distinction matters enormously.
Multiple studies began noticing that lifelong endurance athletes often had more detectable coronary plaque and higher calcium scores than expected. This was particularly noted in older male marathon runners, elite cyclists, and long-term triathletes. In some studies, athletes actually had more calcified plaque than sedentary controls.
That sounds alarming until one looks at mortality data. And then the story becomes very strange.
The JAMA Cardiology Study
One of the most important studies examining this issue was published in JAMA Cardiology. Investigators evaluated more than 21,000 men with varying physical activity levels and coronary calcium scores.
The findings were remarkable. Individuals with the highest levels of physical activity were more likely to have elevated CAC scores, yet high physical activity was not associated with increased all-cause or cardiovascular mortality, even among those with clinically significant calcium scores.
In other words, highly active individuals often had more calcium, but they were not dying more frequently. That created what many now call the endurance athlete paradox.
Why Might Athletes Develop More Calcium?
Several theories exist.
One involves simple mechanical reality. Endurance exercise places extraordinary repetitive stress on the cardiovascular system. Lifelong runners and cyclists spend years generating elevated cardiac output, repeated surges in blood pressure, and immense vascular shear stress. The coronary arteries are not passive plumbing. They are living tissues constantly adapting to mechanical forces. Some researchers believe this repeated stress may accelerate arterial remodeling and calcification.
Another theory involves oxidative stress and inflammation. Extreme endurance exercise transiently raises catecholamines, inflammatory cytokines, and oxidative stress markers. Even healthy athletes may show temporary increases in troponin or CRP after ultra-endurance events. Usually this resolves completely, but after decades of repeated exposure some researchers wonder whether cumulative vascular effects may occur.
For years many sports cardiologists found reassurance in the “stable plaque” hypothesis. The idea was that endurance athletes might develop denser, more calcified, and therefore more stable plaque. Calcified plaque is generally thought to be less rupture-prone than soft inflammatory plaque, which is more likely to trigger acute heart attacks.
Then came a study that complicated the narrative.
MASTER@HEART
The highly discussed MASTER@HEART study examined lifelong endurance athletes, late-onset athletes, and healthy non-athletic controls.
The study found lifelong endurance athletes had higher overall plaque burden and more calcified plaque, but also more mixed and non-calcified plaque in some coronary segments.
That challenged the reassuring assumption that athlete plaque is always the “safe” stable kind.
Importantly, however, the study did not demonstrate increased mortality. It mainly examined imaging findings rather than clinical events.
So we now sit in an interesting scientific tension: imaging studies suggest more plaque in some endurance athletes, while mortality studies continue to show remarkably favorable longevity outcomes.
VO2 Max Still Matters
One reason the mortality data remain favorable may be that cardiorespiratory fitness itself is one of the strongest predictors of longevity in all of medicine.
A major JAMA Network Open study involving more than 120,000 individuals found that higher cardiorespiratory fitness was strongly associated with lower mortality, with no obvious upper limit of benefit observed in the highest fitness groups.
That is a powerful finding. Fitness itself appears profoundly protective.
Still, some researchers suspect there may be a physiologic ceiling where extreme lifelong endurance exercise introduces tradeoffs. Potential concerns discussed in the literature include atrial fibrillation, myocardial fibrosis, right ventricular remodeling, and coronary calcification.
This has led to the concept of a possible U-shaped or reverse-J exercise curve – where sedentary behavior is harmful, moderate-to-high exercise is profoundly protective, and extreme decades-long endurance exposure may introduce unique cardiac remodeling phenomena in some individuals.
This does not mean endurance exercise is dangerous. It means biology is nuanced, which is often far less satisfying than slogans.
Context Matters
A coronary calcium score of 300 in a diabetic smoker with metabolic syndrome may represent something biologically very different from the same score in a lean lifelong cyclist with excellent insulin sensitivity, low inflammation, superb VO2 max, and exceptional metabolic health.
The scan number is identical. The physiologic context may not be. Modern sports cardiology increasingly recognizes this distinction.
I have quite a few patients that exhibit the athlete’s paradox, and we address their artery health in the same way we do all our patients, with additional imaging such as the carotid ultrasound and advanced lipid studies.
The Big Picture
The current evidence still overwhelmingly supports exercise as one of the most powerful longevity interventions ever discovered. But the newer data suggest something more sophisticated than the old simplistic narrative.
Exercise is not merely “good” or “bad.” It is a biologic stressor. And like many stressors, too little is harmful, the right amount is adaptive, and enormous lifelong doses may produce unexpected remodeling in some tissues.
For now, the endurance athlete paradox remains unresolved: some of the fittest people on Earth may carry more coronary plaque than expected, yet still outlive most of the population around them.
Author
Scott Rollins, MD, is Board Certified with the American Board of Family Practice and the American Board of Anti-Aging and Regenerative Medicine. He specializes in bioidentical hormone replacement for men and women, thyroid and adrenal disorders, fibromyalgia and other complex medical conditions. He is founder and medical director of the Integrative Medicine Center of Western Colorado (www.imcwc.com) and Bellezza Laser Aesthetics (www.bellezzalaser.com). Call (970) 245-6911 for an appointment or more information.
