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Clinical Review | Cardiovascular | Emergency Medicine
Marathon Running & Sudden Cardiac Arrest: New Study Reviews the Findings of the Last Decade
Time to read: 06:47
Time to listen: 11:06
Published on MedED: 2 April 2025
Originally Published: 30 March 2025
Source: JAMA Network
Type of article: Clinical Research Summary
MedED Catalogue Reference: MCIB007
Category: Cardiovascular Disease
Cross-reference: Emergency Medicine
Keywords: sudden cardiac death, cardiac myopathy, marathon running, sports medicine
Originally Published in JAMA Network 30 March 2025. This is a summary of the clinical study and in no way represents the original research. Unless otherwise indicated, all work contained here is implicitly referenced to the original author and trial. Links to all original material can be found at the end of this summary. Access the Disclaimer
Key Take Aways
1. Cardiac arrest incidence in long-distance runners has increased slightly since 2020, with male marathon runners at the highest risk.
2. Despite this rise, the risk of cardiac death has declined by 49% since 2010 due to improved emergency response, including bystander CPR and AED use.
3. Most cardiac arrests occur in the final race quartile, often linked to increased exertion, with coronary artery disease as the leading cause of mortality in these participants
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Study Context | Objectives | Study Design | Findings | Discussion| Limitations | Conclusion | Original Research | Funding | References
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South Africa is a nation passionate about long-distance running, with a deep-rooted history in endurance events. In 2024 alone, the country hosted 129 officially sanctioned races, including 106 standard marathons and 22 ultra-marathons (56 km or longer). These events drew a combined 121,480 finishers, with the Comrades Marathon (17,305), Cape Town Marathon (16,351), and Two Oceans Marathon (10,178) ranking the most well-attended races. 1
While the physical and mental benefits of distance running are well established, the sport also carries inherent health risks, particularly cardiovascular complications.
Marathon running has been associated with an increased likelihood of medical encounters (MEs) during races, including sudden cardiac arrest (SCA) and sudden cardiac death (SCD).2,3 The incidence of SCD in long-distance races is estimated to range between 0.3 and 5 per 100,000 participants, while SCA occurs in approximately 0.54–2.5 per 100,000 participants 4,5,6
Recognizing the importance of standardized reporting on race-related medical events, an international consensus statement was published in 2019, outlining criteria for documenting medical encounters at endurance events. 7
Serious MEs, including acute coronary syndromes, SCA, and SCD, remain the most concerning outcomes for race organizers and healthcare providers. Several studies from North America and Europe have identified coronary artery disease as a leading cause of SCA and SCD among marathon runners. For instance, a 2010 study found that 21 of 26 sudden deaths reported across 26 U.S. marathons were attributed to underlying coronary artery disease, while other cases were linked to congenital anomalies, electrolyte imbalances, or exertional heat stoke.8
South Africa has also contributed to the growing body of research on race-related medical incidents. A 2025 study by Green et al. examined medical encounters over six years at the Cape Town Marathon, analysing data from 40,446 race starters. The study reported an overall incidence of 8.7 medical encounters per 1,000 participants, with cardiovascular-related issues being the most frequent cause. Notably, while no cases of SCD or SCA were documented, acute coronary syndromes accounted for a significant proportion of serious, life-threatening events.9
Despite these findings, the rising popularity of endurance events and growing awareness of potential cardiac risks have led to improved racecourse medical coverage and emergency action planning. As more data emerge, a clearer picture of cardiovascular pathology among endurance athletes is developing. However, the need for ongoing surveillance, preventative strategies, and athlete education remains critical.
The researchers of this study undertook to determine the incidence and outcomes of cardiac arrests during US marathons and half-marathons between 2010-2023, providing insights into the incidence, causes, and survival outcomes of such events in endurance sports.
Case profiles were reviewed to assess the causes of cardiac arrest and factors influencing survival. Incidence and aetiology data were compared with historical benchmarks from 2000 to 2009.
Cardiac arrest was defined as a pulseless, unconscious state confirmed by a medical professional. Decedents were individuals who could not be resuscitated on-site or died before hospital discharge, while survivors were those successfully resuscitated and later discharged from the hospital.
Findings
Cardiac arrest rates remained stable from 2010 to 2019 but increased from 2020-2023 (0.81 per 100,000). Despite this, the fatality rate dropped significantly compared to 2000-2009 (71% vs. 34%).
Between 2010 and 2023, 29.3 million people completed marathons and half-marathons in the US
The researchers determined that there were 176 reported cardiac arrests (1 per 166,667 participants). 59 of these cases were fatal. (1 per 500,000).
Cardiac arrests were more frequent in marathons (1.04 per 100,000) than in half-marathons (0.47 per 100,000).
Of the 176 incidents, the majority occurred in men (127), while 19 involved women. The gender of the remaining thirty cases was unknown.
Survivors tended to be older (47.6 vs. 34.4 years), and there was no significant difference between the genders in this group.
Causes
The cause of cardiac arrest was identified in 67 cases, with coronary artery disease being the most common (40%).
Unexplained causes of cardiac arrest accounted for 25% of cases, and 47% of these patients survived.
Hypertrophic cardiomyopathy was rare (7%), while exertional heat stroke accounted for 6% of cardiac arrests (3 fatalities).
Aetiology
Among the fatal cases, autopsies identified coronary artery disease in 9 individuals (including acute plaque rupture and stable disease).
Of 7 cases classified as sudden arrhythmic death, genetic testing revealed uncertain variants in cardiomyopathy genes in 4 of the deceased.
Toxicology reports found stimulants (caffeine, amphetamines, pseudoephedrine) in 4 deceased individuals.
Interventions
Longer CPR times (risk ratio 1.2 per 5 minutes) and initial rhythms of pulseless electrical activity/asystole (risk ratio 2.5) were linked to higher mortality.
The findings from this study provide valuable insights into the incidence of cardiac issues during long-distance races, particularly marathons, and the evolving trends over time.
Although the overall incidence of cardiac arrests has remained relatively stable over the past two decades, the risk of sudden cardiac death (SCD) has notably decreased by approximately 49% since 2010. This decline is likely due to improvements in emergency action planning, including the widespread implementation of bystander CPR and the increased availability of automated external defibrillators (AEDs) at race events.
However, cardiac arrest remains a serious concern, particularly among male marathon runners and older participants, where the incidence of cardiac arrest continues to be higher. The primary cause of these arrests is coronary artery disease, with less common causes such as hypertrophic cardiomyopathy playing a smaller role than previously thought. The study highlights that the majority of cardiac arrests occur during the final stages of a race, suggesting that increased exercise intensity toward the finish line may be a contributing factor.
While the study notes a slight increase in cardiac arrest incidence since 2020, the reasons for this trend remain unclear. Additionally, the study revealed an unexpected finding regarding the potential link between energy drinks and cardiac arrest. A recent study reported a temporal association between cardiac arrest and energy drink consumption, particularly in athletes with ion channelopathies. This warrants consideration in advising runners about potential risks related to stimulant use before or during races.
Given the rising popularity of long-distance running events, there is an urgent need to focus on primary prevention strategies, especially for older runners. Continued improvements in race medical planning, including strategic placement of AEDs and training more race participants in CPR, could further reduce cardiac arrest-related fatalities and improve outcomes for affected runners.
Limitations
This study has several limitations that could impact the findings. First, the case ascertainment methodology differs from the RACER 2000-2009 study, as new methodologies were introduced after 2010, which may have affected comparisons between the two periods. Additionally, race finishing times were used as surrogates for participants, potentially leading to an underestimation of cardiac arrest risk, as some runners may have been counted more than once. Finally, only around 50% of cardiac arrest causes could be identified, and incomplete clinical profiles were available, which introduces the potential for selection bias. However, this was consistent with previous RACER analyses.
Given the rising popularity of long-distance running events, there is an urgent need to focus on primary prevention strategies, especially for older runners. Continued improvements in race medical planning, including strategic placement of AEDs and training more race participants in CPR, could further reduce cardiac arrest-related fatalities and improve outcomes for affected runners.
Access the Study
Kim JHRim AJMiller JT, et al. Cardiac Arrest During Long-Distance Running Races. JAMA Published online March 30, 2025. doi:10.1001/jama.2025.3026
Conflict of Interest, Funding and Support
Conflict of Interest Disclosures
Full declaration is available online
Funding/Support
This work was supported by NIH/National Heart, Lung, and Blood Institute grant R01HL162712 (Dr Kim).
Role of the Funder/Sponsor
No information available
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References
2. Sanchez LD, Corwell B, Berkoff D. Medical problems of marathon runners. Am J Emerg Med. 2006;24(5):608–615. doi: 10.1016/j.ajem.2006.01.023
3. Roberts WO, Roberts DM. A 12-yr profile of medical injury and illness for the twin cities marathon. Med Sci Sport Exerc. 2000;32:1549–1555. doi: 10.1097/00005768-200009000-00004
4. Kim JH, Malhotra R, Chiampas G, et al. Cardiac arrest during long-distance running races. N Engl J Med. 2012;366(2):130–140. doi: 10.1056/NEJMoa1106468
5. Gerardin B, Guedeney P, Bellemain-Appaix A, et al. Life-threatening and major cardiac events during long-distance races: updates from the prospective RACE PARIS registry with a systematic review and meta-analysis. Eur J Prev Cardiol. 2021;28(6):679–686. doi: 10.1177/2047487320943001
6. Tunstall Pedoe DS. Marathon cardiac deaths. Sport Med. 2007;37(4):448–450. doi: 10.2165/00007256-200737040-00046
7. Schwellnus, M., Kipps, C., Roberts, W. O., et al. (2019). Medical encounters (including injury and illness) at mass community-based endurance sports events: an international consensus statement on definitions and methods of data recording and reporting. British journal of sports medicine, 53(17), 1048–1055. https://doi.org/10.1136/bjsports-2018-100092
8. Day SM, Thompson PD. Cardiac risks associated with marathon running. Sports Health. 2010 Jul;2(4):301-6. doi: 10.1177/1941738110373066. PMID: 23015951; PMCID: PMC3445091.
9. Green, D., Sewry, N., Derman, W., Killops, J., Boer, P. H., Jordaan, E., & Schwellnus, M. (2025). A high incidence of serious life-threatening cardiovascular medical encounters during a marathon (2014-2019) calls for prevention strategies: SAFER XL. The Physician and Sportsmedicine, 53(1), 55–63. doi: 10.1080/00913847.2024.23994957
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