Can Running Cause a Heart Attack? The Underlying Risks

Running can trigger a heart attack or sudden cardiac arrest, but the absolute risk is remarkably small. Among more than 10.9 million participants in long-distance races over a decade, cardiac arrest occurred at a rate of about 0.54 per 100,000 runners, and roughly seven in ten of those cases were fatal. The relationship between running and cardiac danger is more layered than a simple yes-or-no, though, because the same activity that poses a tiny acute risk also powerfully protects the heart over time.

How Often Do Runners Actually Die?

The numbers are consistently reassuring in absolute terms. A review pooling data from more than 4 million marathon participants found an overall sudden-death incidence of roughly 1 in 114,000 runners. When nonfatal cardiac arrests were included, the rate rose to between 1 in 31,000 and 1 in 55,000.¹ A separate study looking specifically at U.S. marathons between 2000 and 2009 identified 28 deaths among roughly 3.7 million finishers, for a death rate of 0.75 per 100,000.²

Full marathons carry a higher risk than half-marathons. In the largest study on this question, the cardiac arrest rate during marathons was about 1.01 per 100,000, compared with 0.27 per 100,000 during half-marathons. Men were at considerably higher risk than women, with arrest rates roughly five to six times greater. Male marathon runners were the highest-risk subgroup, and their incidence appeared to increase during the latter half of the study period.³ Why the rate rose among men is not fully understood, though an aging marathon population and the growing popularity of the distance among less-trained runners are possible contributors.

What Actually Happens Inside the Heart

The phrase “heart attack” in everyday language usually means a blocked coronary artery cutting off blood supply. The medical version of that, a myocardial infarction, does happen during running, but it is only one part of the picture. The broader category, sudden cardiac arrest, includes any abrupt loss of heart function, whether from a blocked artery, a rhythm disturbance, or a structural defect. Most exercise-related cardiac emergencies fall into this wider bucket.

For runners older than about 45, the dominant mechanism looks a lot like a classic heart attack. In an autopsy study of men who died during exertion, plaque rupture was found in 68% of cases, compared with 23% of men who died at rest. Both physical exertion and an unfavorable cholesterol profile independently predicted plaque rupture.⁴ During intense exercise, changes in blood-vessel tone and the mechanical shear forces on artery walls can destabilize a vulnerable plaque, especially one with a thin fibrous cap. The plaque cracks open, a clot forms, and the artery blocks.⁵ In the U.S. marathon mortality data, atherosclerotic heart disease or myocardial infarction accounted for 93% of deaths in runners aged 45 and older.²

Why Younger Runners Die From Different Causes

In runners under about 35 to 40, the causes shift dramatically. These deaths are overwhelmingly driven by inherited or congenital heart conditions that went undetected. The most common culprit in young athletes is hypertrophic cardiomyopathy, a condition in which part of the heart muscle is abnormally thick, creating a setup for dangerous rhythm disturbances under stress.⁶ Other structural conditions, like anomalous coronary arteries and arrhythmogenic cardiomyopathy, also feature prominently in younger victims.⁷

Beyond structural defects, a group of electrical disorders called channelopathies can cause the heart to short-circuit during exertion. Long QT syndrome, Brugada syndrome, and catecholaminergic polymorphic ventricular tachycardia are among the conditions that may leave a heart looking perfectly normal on an autopsy table but fatally prone to rhythm chaos when adrenaline surges.⁸ A U.K. pathological study found that 23% of athletes who died suddenly had a structurally normal heart at autopsy, pointing to these invisible electrical conditions as the likely explanation.⁹

The Exercise Paradox

This is where the science gets genuinely interesting and a little counterintuitive. Vigorous exertion transiently increases the risk of a cardiac event in any given moment, but habitual exercise dramatically lowers the overall risk. An American Heart Association scientific statement put it plainly: the incidence of both heart attack and sudden death is highest in people who are habitually the least active. A disproportionate number of exercise-triggered events happen when sedentary people perform unaccustomed physical activity.¹⁰

Regular exercise lowers both the baseline risk of a cardiac event and the relative risk that any single bout of exertion will trigger one.¹¹ So a trained runner logging consistent weekly mileage is in a fundamentally different risk category from someone who is sedentary most of the year and then runs a charity 10K. The practical takeaway is not to avoid running but to build up gradually and maintain consistency.

Troponin After a Marathon and Why It Usually Doesn’t Mean Damage

If you have ever had blood drawn after a long race, you might have been alarmed to hear that your cardiac troponin was elevated. Troponin is a protein that leaks out of heart-muscle cells and is the standard blood marker doctors use to diagnose a heart attack. After a marathon, the majority of runners show some troponin elevation. In a study of Boston Marathon runners, 68% had detectable troponin increases after the race, and about 11% had levels in the range that would normally trigger concern in an emergency room.¹² With more sensitive assays, the proportion jumps to 86%.¹³

The good news is that detailed imaging studies suggest this release is not from permanent damage. Marathon running causes temporary dilation of the right side of the heart, a short-lived drop in right ventricular function, and the release of troponin and B-type natriuretic peptide, but these changes do not appear to reflect actual ischemic injury to any chamber.¹⁴ The working theory is that prolonged mechanical stress on heart-muscle membranes allows small amounts of troponin to leak without the cells dying. Levels typically normalize within a day or two. Still, if you experience chest pain, lightheadedness, or unusual breathlessness during or after a race, those symptoms deserve immediate medical evaluation regardless of what troponin “usually” does.

What Decades of Hard Training Can Do to the Heart

The long-term effects of endurance exercise on the heart are a growing area of research, and some findings have surprised cardiologists. One study using CT coronary angiography found that male endurance athletes had a higher prevalence of coronary artery plaques than sedentary men of the same age, with 44% of athletes showing some degree of plaque versus 22% of controls. The athletes also had more coronary calcium, and the number of years spent training was the only independent predictor of higher calcium scores and significant narrowing.¹⁵

There is a potentially important wrinkle, though. The plaques in athletes were predominantly calcified, while sedentary men had mostly mixed-morphology plaques. Calcified plaques are generally considered more stable and less likely to rupture than the soft, lipid-rich plaques that cause most heart attacks. Whether the coronary calcium seen in veteran athletes carries the same risk as calcium in the general population is still debated.

Myocardial fibrosis, meaning small patches of scar tissue in the heart muscle, is another finding that turns up more often in long-term endurance athletes. A systematic review found the prevalence ranged from 13% to 48% depending on the study. The scarring was mostly focal and located at the junction where the right ventricle inserts into the septum, a spot that endures significant mechanical stress during prolonged exercise.¹⁶ In one study of lifelong veteran male athletes, half showed evidence of fibrosis on cardiac MRI, compared with zero cases in age-matched sedentary controls. The amount of fibrosis was strongly associated with years of training and the number of marathons and ultramarathons completed.¹⁷ Whether these patches of scar tissue increase the risk of dangerous arrhythmias or are benign adaptations remains an open question, but they do provide a plausible substrate for rhythm disturbances in otherwise healthy-looking athletes.

Atrial Fibrillation and the Endurance Runner

Atrial fibrillation, the most common sustained heart-rhythm disorder, appears to be more prevalent among long-term endurance athletes than in the general population. Studies of experienced marathon runners have estimated AF prevalence at roughly 5% to 10%, with one study finding a 3.3% incidence specifically among male non-elite marathon runners.¹⁸ For context, the general population rate for adults in a similar age range is usually estimated at 2% to 4%, so the excess risk is real but modest. AF itself rarely causes sudden death, but it can increase the risk of stroke and may interact with other cardiac changes in athletes who also have fibrosis or structural remodeling.

Heat, Dehydration, and Over-the-Counter Painkillers

The cardiac risk of running does not exist in a vacuum. Environmental and pharmacological factors can amplify danger significantly. Heat stroke is one of the more dramatic examples. Severe hyperthermia during exercise can trigger sinus tachycardia, atrial fibrillation, and in the worst cases, ventricular arrhythmias and cardiac arrest. QT prolongation from electrolyte disturbances and conduction abnormalities add further risk layers.¹⁹ Hot, humid race conditions are a known multiplier for cardiac events, which is one reason many major marathons schedule start times before dawn.

NSAIDs like ibuprofen are another underappreciated concern. Many runners pop ibuprofen before or during a race to manage muscle pain, but the practice carries real risks. A scoping review found that marathon runners taking ibuprofen had an average drop in blood sodium of about 2 mmol/L compared with a rise in controls, increasing the danger of exercise-associated hyponatremia, a potentially life-threatening condition. In one ironman study, 100% of athletes who developed hyponatremia had taken NSAIDs. NSAID use was also associated with a higher rate of acute kidney injury during ultra-endurance racing.²⁰ These kidney and electrolyte problems are relevant to cardiac risk because severely disordered potassium or sodium can trigger lethal arrhythmias.

Pre-Participation Screening

Whether runners should be screened for hidden heart conditions before competing is one of the more contentious topics in sports medicine. The American Heart Association recommends a 12-point screening procedure based on personal and family history plus a physical exam, with additional testing only when something suspicious comes up. The European Society of Cardiology takes a different approach and includes a resting electrocardiogram (ECG) at every evaluation, arguing it catches most cases of hypertrophic cardiomyopathy and arrhythmogenic cardiomyopathy.²¹

The AHA’s resistance to universal ECG screening comes down to cost-effectiveness and false positives. An abnormal ECG in a healthy athlete may lead to expensive follow-up testing and significant psychological distress, sometimes for findings that turn out to be harmless adaptations of an athletic heart. Italy, which has mandated ECG-inclusive screening for competitive athletes since the 1980s, reported a roughly 90% reduction in sudden cardiac death among young athletes over the program’s lifespan.²² That result is striking, though critics point out the data come from a single country with a unique healthcare structure, making it hard to generalize. For recreational runners who are not subject to any mandatory screening, the evidence still supports a basic conversation with a doctor about family history and symptoms before taking on a marathon.

Why Rapid Response at Races Saves Lives

When a runner does go into cardiac arrest during a race, the speed of response matters enormously. A Japanese study of marathon-related cardiac arrests found that when bystander CPR was started within one minute and defibrillation was performed within three minutes, full neurological recovery at one year was achieved in over 95% of cases.²³ That survival rate is dramatically better than the general out-of-hospital cardiac arrest survival rate, which is typically in the single digits to low teens in most countries.

The reason races can achieve such outcomes is logistics. Courses can be lined with medical volunteers, automated external defibrillators can be staged at regular intervals, and the victim is already in a public setting where someone trained in CPR is likely nearby. This is a strong argument for running organized races over solo efforts if you have any cardiac risk factors, because the safety net is vastly better. For anyone who trains alone, carrying identification that lists medical conditions and emergency contacts is a minimal but worthwhile precaution.

Who Should Be Most Cautious

The evidence points to several groups that deserve extra vigilance before and during running. Sedentary individuals ramping up quickly face the highest relative risk from a single exertion bout. Men over 40 with traditional cardiovascular risk factors like high cholesterol, high blood pressure, smoking history, or a family history of early heart disease are the demographic most likely to suffer plaque-rupture events during exercise. Young athletes with unexplained fainting episodes, a family history of sudden death under age 50, or unusual shortness of breath out of proportion to fitness level should pursue cardiac evaluation before competitive running.

Longtime endurance athletes are in a more ambiguous position. The coronary calcium and fibrosis findings are concerning on paper, but there is no clear evidence yet that these changes translate into a higher rate of heart attacks in the way that identical findings in sedentary people do. The research is still catching up to the question. In the meantime, veteran runners who notice new symptoms like palpitations, unexplained fatigue during efforts that used to be easy, or brief episodes of lightheadedness should bring those to a cardiologist rather than writing them off as aging.