On the first Sunday of October 2026, runners died at the Portland Marathon, the Milwaukee Lakefront Half and the Cardiff Half. A week later another runner collapsed near the finish of a half marathon in Seoul and died. No cause has been published for any of the four. Deaths like these are rare. In US marathons and half marathons, about one finisher in 500,000 dies of a cardiac arrest during the race, and that share has halved since the 2000s.
About 1 in 500,000 finishers dies
The numbers come from the Race Associated Cardiac Event Registry, known as RACER. Its researchers tried to find every cardiac arrest at a US marathon or half marathon from January 2010 to December 2023. They gathered cases from media reports, race directors, USA Track & Field claims and interviews with survivors or their families.
The team reached about 70% of race directors directly, according to Dr. Jonathan Kim. He is an associate professor at Emory School of Medicine and one of the researchers behind the registry. "The vast majority of cases were identifiable by public search engines," he said. "And all of the deaths were as well."
From 2010 to 2023, 29.3 million runners finished a US marathon or half marathon. The registry found 0.60 cardiac arrests per 100,000 finishers. About a third of those runners died, which works out to roughly one finisher in 500,000. The study was published in JAMA in 2025.
The same group had counted the previous decade for a 2012 paper in the New England Journal of Medicine. That study found 0.54 arrests per 100,000 finishers. The newer study counted about three times as many finishers, and the arrest rate stayed roughly where it was. The rate did rise to 0.81 per 100,000 in 2020-2023, which the authors say needs more study.
Survival has more than doubled since the 2000s
In 2000-2009, 29% of runners who went into cardiac arrest at a race survived. In 2010-2023, 66% did, and the share kept rising through those years. With the arrest rate flat, the death rate per finisher fell by half.
The study records what changed for the runners who collapsed. In 2000-2009, a little over half got CPR from a bystander, and fewer than half had a defibrillator used on them. In 2010-2023, every runner whose case was fully documented got bystander CPR. Defibrillator use was close to universal. Runners who survived tended to have needed CPR for less time. They were also more likely to have had a fast, chaotic first rhythm, which is the kind a defibrillator can shock back to normal. "That's the difference," Kim said of the CPR and defibrillators.
The 2025 paper says emergency planning with immediate access to defibrillation "may explain the improvement in survival." An observational registry cannot prove the cause. According to the American College of Cardiology's summary, the JAMA editorial published with the study also credited emergency action planning for the drop in deaths.
Which runners are most at risk of cardiac arrest?
The full marathon carries about twice the risk of the half. For a runner weighing the two distances, that is the clearest difference in the data. Men had about six times as many arrests per finisher as women.
Researchers found a cause in about half of the cases with a full profile. The most common was coronary artery disease, the narrowing of the arteries that feed the heart. It accounted for 27 of the 67 arrests with a known cause. Hypertrophic cardiomyopathy, a thickening of the heart muscle, was uncommon.
Of the 27 runners whose arrest came from coronary disease, 25 survived. That made it the most survivable cause. Survivors overall were older than the runners who died, with a mean age of 47.6 against 34.4.
Research like RACER can pick out who is at risk. In Kim's words, these are "more commonly older individuals with unrecognized cardiovascular risk factors." Identifying them "doesn't mean they can't run a race," he said. He sees it instead as a chance to improve their preventive heart care and "potentially further reduce the risk of cardiac arrest during these events."
Most arrests come in the last quarter of the race
RACER found that most arrests happened in the last quarter of the race, though the paper gives no exact count. NYRR medical director Dr. Matt Friedman puts the share of serious cardiac events in the last quarter at 65%. For that reason NYRR placed an ECMO machine at the finish of the Brooklyn Half in May 2026. Friedman called ECMO "sort of a last-ditch effort for a person in cardiac arrest who does not respond to normal resuscitative measures."
At the London Marathon, however, fewer than a third of cardiac arrests happened at the finish, according to a 2007 review. The rest happened anywhere between mile 6 and mile 26.
Medical cover at races in New York, Chicago and London
Medical cover is easiest to see at the biggest races on the marathon calendar. At the 2026 Brooklyn Half, NYRR placed response units about every half mile along the course. Each one carried a defibrillator. At the 2024 New York City Marathon, medical tents stood along the course as well as at the start and the finish.
Chicago's medical director described a similar setup in 2010. Each of the race's 21 aid stations had a defibrillator. Paramedics worked the course on bikes and golf carts, and foot teams carried defibrillators.
In 2017 the cardiac team from St George's hospital supported the London Marathon with five mobile cardiac ambulances and ambulance stations.
Can a heart check before race day find the risk?
The American College of Sports Medicine says exercise-related heart events "are often preceded by warning signs/symptoms." It also says the risk falls as people become fitter. The American Heart Association warns that hard exercise, "particularly when performed by unfit individuals," can raise the short-term risk of sudden cardiac death in people who are susceptible. A symptom that shows up in training is a reason to see a doctor before race day.
The 2007 review of the London Marathon shows the limit of that advice. It counted eight runners who died of cardiac causes at the race. Only one of them had told his family or doctor about symptoms that suggested heart disease. He had reported chest pain before the marathon and passed an exercise stress test. He died anyway with a narrowed left anterior descending coronary artery.
"If you're going to take on strenuous exercise later in life, and especially if you have active heart disease," said Dr. William Roberts of the University of Minnesota, "it's clearly in your interest to be tested and make sure you can handle it."
The other thing a runner can do is learn CPR. The 2012 study found bystander CPR was one of the strongest predictors of survival, and anyone on the course can be the bystander. Kim's recommendation for races is "to make CPR training available to race participants and to strategically place defibrillators along the racecourse."
Further reading
- Cardiac arrest in US marathons and half marathons, 2010-2023 (JAMA 2025, PubMed abstract): the RACER study behind the incidence and survival figures.
- Full text of the 2025 RACER paper in JAMA: causes, ages, CPR and defibrillator use, and the 2020-2023 rise.
- Cardiac arrest during long-distance running races (NEJM 2012, PubMed abstract): the 2000-2010 baseline.
- American College of Cardiology summary of RACER: a short digest with the editorial's view.
- Emory release on the study, via ScienceDaily: Dr. Jonathan Kim on how cases were found and what made the difference.
- Brooklyn Half adds an ECMO machine at the finish (Brooklyn Paper): NYRR's 2026 medical plan and Dr. Matt Friedman's figures.
- The 2024 NYC Marathon medical operation (CrowdRx): volunteer, staff and tent counts.
- Chicago Marathon medical planning (JEMS, 2010): George Chiampas on defibrillators and course teams.
- St George's cardiac team at the 2017 London Marathon: the race's cardiac cover.
- Sudden death at the London Marathon (Sports Medicine 2007, PubMed abstract): the 1 in 80,000 death rate and the runner who passed a stress test.
- ACSM exercise preparticipation screening recommendations (2015, PubMed abstract): warning symptoms and who should be screened.
- American Heart Association statement on exercise and heart risk (Circulation 2020, PubMed abstract): the acute risk of vigorous exercise in unfit, susceptible people.
