OBJECTIVE: To investigate the incidence and assess the outcomes of cardiac arrest occurring in the context of participation in marathon or half-marathon races. DESIGN: Incidence study. SETTING: Data came from long-distance race records in the United States from January 1, 2001, to May 31, 2010. PARTICIPANTS: All participants were registered entrants in the long-distance races. Participation statistics (sex, participant identity numbers, and race distance) were publicly accessible from Running USA. ASSESSMENT OF RISK FACTORS: Data on possible risk factors for cases were obtained retrospectively through computer searches (age, sex, location of cardiac arrest, publicly released cause of death). Three attempts were made to obtain information from survivors or from the next-of-kin of deceased cases. This information included demographic characteristics, exercise and running history, and personal and family medical history. MAIN OUTCOME MEASURES: The main outcome measures were the incidence and characteristics of cases of cardiac arrest that occurred during the race, at the finish-line, or ≤ 1 hour after completion of a marathon or half marathon. Cardiac arrests were defined by a medical professional as an unconscious state and an absence of spontaneous respirations and pulse. Successful resuscitation and discharge from hospital defined a survivor, whereas a nonsurvivor was a person who was not successfully resuscitated in the field or who died before hospital discharge. Cases of cardiac arrest had to be independently identified in 3 separate sources of data or confirmed with official race medical staff. Further information, including details of the cardiac arrest, was obtained from medical records and autopsies and the survivors or next of kin. MAIN RESULTS: Among 10.9 million registered race participants there were 40 cardiac arrests in marathons and 19 in half marathons (overall incidence, 0.54 per 100,000; 95% confidence interval [CI], 0.41-0.70). The mean age of runners with cardiac arrest was 42 (SD 13) years and 86% were men. The incidence per 100,000 was higher in marathons (1.01; 95% CI, 0.72-1.38) than in half marathons (0.27; 95% CI, 0.17-0.43; and among men (0.90; 95% CI, 0.67-1.18) than among women (0.16; 95% CI, 0.07-0.31). More runners died than survived the cardiac arrest (42 [71%] vs 17[29%]); the incidence of sudden death was 0.39 per 100,000 participants (95% CI, 0.28-0.52). The mean age of the nonsurvivors was younger than that of the survivors (39 vs 49 years; P = 0.002). Complete clinical information on cause of death was available for 23 runners. The most common confirmed or possible cause of death was hypertrophic cardiomyopathy (15 cases, of whom 9 had an additional clinical factor). Among the 8 survivors with complete information, ischemic heart disease was the cause of cardiac arrest in 5. The survivors were older than nonsurvivors (53 vs 40 years), had completed more long-distance races, and were more likely to have known cardiac risk factors. The strongest predictors of survival were initiation of cardiopulmonary resuscitation by bystanders (P = 0.01) and an underlying diagnosis other than hypertrophic cardiomyopathy (P = 0.01) CONCLUSIONS:: The incidence of cardiac arrest and sudden death per 100,000 runner hours was 0.2 and 0.14. Risk factors for cardiac arrest were full marathon and male sex. Younger age and no previous knowledge of cardiovascular risk were associated with sudden death.
