Defibrillators and CPR cut marathon cardiac deaths in half, study shows

By Priyanjana Pramanik, MSc.Reviewed by Susha Cheriyedath, M.Sc.Mar 31 2025

Despite a steady rate of race-related cardiac arrests, a major drop in deaths points to one life-saving solution: rapid CPR and defibrillation on the course.

Study: Cardiac Arrest During Long-Distance Running Races. Image Credit: Pavel1964 / Shutterstock

In a recent study published in the Journal of the American Medical Association, researchers examined the incidence and outcomes of cardiac arrests among American half-marathon and marathon runners from 2010 to 2023, using data from survivor interviews, race finishers, race directors, media reports, and claims made to USA Track & Field (USATF), the national governing body for the sport.

Their findings indicate that the incidence of cardiac arrest remained stable from 2010 to 2023, compared to 2000–2009. However, mortality risk attributed to cardiac arrest events during races decreased by nearly 50%, which the research team attributed to improvements in emergency response, particularly access to quicker defibrillation.

Background

Long-distance running in the U.S. has grown significantly since 2010, with an estimated 29.3 million half-marathon and marathon finishers, nearly three times the number of runners between 2000 and 2009. This increased participation has led to greater awareness of potential risks and improved medical coverage for all races.

The Race Associated Cardiac Event Registry (RACER) previously reported a low incidence of cardiac arrests in long-distance races but found that male marathon runners were at higher risk, with hypertrophic cardiomyopathy as the leading cause and a high mortality rate of more than 70%.

Since then, advances in the detection of cardiac events, molecular autopsies, race participant demographics, and broader access to automated external defibrillators (AEDs), bystander cardiopulmonary resuscitation (CPR) may have influenced outcomes. However, the combined effects of these developments remain unclear.

About the Study

In this study, researchers aimed to update knowledge on the incidence, causes, and outcomes of survival or mortality following cardiac arrests in half-marathons and marathons, considering the effects of evolving emergency measures and the coronavirus disease 2019 (COVID-19) pandemic.

They employed a prospective observational design, utilizing data from RACER, to examine cardiac arrest incidence, outcomes, and causes among U.S. participants in half-marathons and marathons from 2010 to 2023.

Race participation data were obtained from Running USA, a non-profit organization that tracks race information. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines were followed by the research team.

Cardiac arrest cases were identified using three approaches: (1) intensive internet searches using specific keywords across 443 certified U.S. races, (2) interviews with race directors (219 out of 317 responded), and (3) review of claims made to the USATF for cardiac arrests. Cases were classified as survivors (discharged from the hospital) or decedents (died before or after resuscitation).

To determine causes, media reports were reviewed, and next of kin or survivors were contacted for additional medical information. Diagnoses were verified and adjudicated by study investigators.

Statistical analysis involved calculating incidence proportions and using Poisson regression to compare rates across different periods, racial types, and sexes. Sensitivity analyses addressed missing data on sex, race, and distance.

Factors associated with surviving the cardiac event, including CPR time and initial cardiac rhythm, were analyzed using multivariable regression. The study also accounted for potential demographic shifts and the impact of COVID-19 on race participation and medical response measures.

Findings

The study analyzed 29.3 million half-marathon and marathon finishers between 2010 and 2023, identifying 176 cases of cardiac arrest (1 per 166,667 participants, 0.6 per 100,000). Among these, 59 (34%) were fatal, while 117 (66%) survived.

Cardiac arrest incidence remained stable from 2010 to 2019 but increased from 2020 to 2023, reaching 0.81 per 100,000, driven primarily by a rise among male marathon runners (2.79 per 100,000 in 2020–2023 vs. 1.43 per 100,000 pre-2020). However, case fatality rates declined significantly, from 48% in 2010–2014 to 25% in 2015–2023.

Men had a significantly higher risk (1.12 per 100,000) than women (0.19 per 100,000). Cardiac arrests were more frequent during marathons (1.04 per 100,000) than half-marathons (0.47 per 100,000). Coronary artery disease represented the most frequent cause (40%), followed by unexplained causes (25%) and hypertrophic cardiomyopathy (7%). Notably, 48% of cases lacked sufficient data for a definitive diagnosis.

Among 36 cases with comprehensive medical profiles, all received bystander CPR, and 97% received AED intervention, improving survival rates. Overall survival among all cardiac arrest cases improved from 29% in the 2000–2009 period to 66% between 2010 and 2023, a rate comparable to survival in public venues equipped with AEDs such as airports, casinos, and schools.

The slight increase in the incidence of cardiac arrests post-2020 remains unexplained, though reduced healthcare access during the COVID-19 pandemic and potential shifts in participant health profiles are possible factors.

Additionally, survivors were significantly older than decedents (mean age 47.6 vs. 34.4 years), suggesting that younger runners may experience more fatal arrhythmic events, while older runners more often survive ischemic events following early intervention.

Toxicology findings also revealed the presence of stimulants—such as caffeine, amphetamines, and pseudoephedrine—in several decedents, particularly in cases of unexplained or arrhythmogenic cardiac arrest. Although not conclusively causal, these findings highlight the need for further exploration of substance use in endurance sports.

Conclusions

Despite a slight increase in the incidence of cardiac arrests since 2020, the risk of cardiac death has declined by 49% since 2010, likely due to improved emergency response, including universal CPR and AED access.

Coronary artery disease remains the primary cause, underscoring the need for improved preventive cardiac care among long-distance runners, particularly older males in marathons. Limitations include incomplete clinical data — nearly half of the cases had undetermined etiologies — and the potential for underestimating risk due to the inclusion of repeat runners.

Future research should investigate the post-pandemic health impacts, participant characteristics by race, and genetic factors in unexplained cases, while also promoting broader cardiac screening and emergency preparedness in endurance sports.