Millions of people participate in long-distance running, particularly marathons and half-marathons, annually.¹ While the health benefits of regular exercise are well established,² long-distance running can cause significant cardiovascular stress, potentially increasing the risk of cardiac arrest in individuals with underlying heart conditions.³ This concern is particularly notable as the number of middle-aged and elderly runners—a population at higher average cardiovascular risk than younger runners—continues to rise.⁴ Understanding the incidence, causes, and outcomes of cardiac arrest in long-distance runners is crucial for informing risk, identifying prevention strategies, and optimizing race-day medical preparedness.

In this issue of JAMA, Kim et al⁵ report on a comprehensive prospective observational study that investigated the incidence and outcomes of cardiac arrest during marathons and half-marathons in the US between 2010 and 2023. Their study provides valuable insights into the incidence, risk factors, etiologies, and survival trends associated with cardiac arrest in long-distance runners.

The researchers used data from the Race Associated Cardiac Event Registry (RACER), a prospective registry of marathon and half-marathon runners in the US.¹ A targeted, multistep algorithm was used to identify cases of cardiac arrest through media reports, direct contact with race directors, and USA Track & Field claims data. This systematic approach minimized the risk of underreporting and ensured a more accurate representation of cardiac arrest incidence. A similar approach was used in an earlier report using RACER data, allowing for comparisons over time.¹

A total of 176 cardiac arrest cases were identified among 29 311 597 race finishers between 2010 and 2023. The incidence of cardiac arrest remained relatively stable over this period compared with the previous decade (2000-2009), with an incidence proportion of 0.54 per 100 000 participants. However, the study revealed a significant decline in cardiac arrest mortality from 2010-2023 compared with 2000-2009 (34% vs 71%, P < .001).^1,5 The study also highlighted key demographic factors associated with higher cardiac arrest incidence. Men were found to be at a higher risk than women, with an incidence rate of 1.12 per 100 000 compared with 0.19 per 100 000 in women. Marathons were associated with a higher incidence proportion of cardiac arrest, compared with half-marathons (1.04 per 100 000 vs 0.47 per 100 000).

Coronary artery disease was identified as the most common cause of cardiac arrest, accounting for 40% of cases. This finding contrasts with earlier studies that identified hypertrophic cardiomyopathy as the predominant cause.¹ The authors suggest that the shift in etiology may be due to improved case ascertainment methods and a potential bias in previous studies toward identifying hypertrophic cardiomyopathy cases. It is also possible that diagnosis and treatment of hypertrophic cardiomyopathy has improved to the point that it now accounts for only a small minority of cardiac arrest cases in marathon runners.

The strengths of the study include its large sample size, comprehensive case identification methods, and detailed analysis of clinical profiles that may help identify individuals at the highest risk for cardiac arrest during long-distance running. The study also has limitations. Race finishing times were used as surrogates for race participants, which may have resulted in some participants being counted more than once. This would have the potential effect to underestimate cardiac arrest risk slightly. There is no reason to believe this limitation would have differed in the prior RACER analysis; thus, relative comparisons between periods are likely still valid. The study was unable to ascertain the cause of cardiac arrest in approximately 50% of cases, which may limit the accuracy of the etiologic findings.

Despite these limitations, the study has important clinical implications. The decline in cardiac arrest mortality likely underscores the importance of effective emergency action planning during races, including immediate access to defibrillation. Rapid access to prehospital automated external defibrillators has been associated with a favorable survival and neurologic outcome in distance runners who experience a cardiac arrest.⁶ The findings of the study also may reinforce the importance of primary cardiac prevention in older runners, particularly men, who are at higher risk of coronary artery disease. This is in line with some lines of thinking that would support use of low-dose aspirin before races to prevent cardiovascular events, including cardiac arrest, in patients with an increased estimated atherosclerotic risk.⁷

This study provides valuable insights into the incidence, causes, and outcomes of cardiac arrest during long-distance running races. While the overall incidence of cardiac arrest has remained stable, the significant decline in mortality highlights the positive impact of improved medical preparedness for races. The study’s findings emphasize the need for continued efforts to enhance primary and secondary prevention strategies for runners, ensuring the safety of participants in long-distance running events.