Meteorological and Environmental Factors Associated With Sudden Cardiac Arrest During Marathons in Japan

BACKGROUND: Sudden cardiac arrest (SCA) during marathons is a rare but life-threatening event. Although underlying cardiovascular conditions have been implicated in race-related SCA, the contribution of environmental factors, including meteorological conditions and ambient air pollution, remains incompletely understood. OBJECTIVES: The objective of the study was to examine the associations of meteorological conditions and ambient air pollutants with SCA during marathon races. METHODS: We conducted a nationwide race-level study in Japan using data from 4.53 million runners participating in Japan Association of Athletics Federations-certified full marathons between April 2011 and March 2020. Race-level SCA counts were linked to meteorological variables at race start, including ambient temperature, humidity, solar radiation, wind speed, precipitation, and air pressure, and to ambient air pollutants including fine particulate matter, suspended particulate matter, photochemical oxidants, sulfur dioxide, nitrogen dioxide, and carbon monoxide. Associations were examined using Poisson regression models with adjustment for race characteristics and participant composition. RESULTS: Among 4.53 million runners, 75 cases of SCA were identified. Ambient temperature at race start was inversely associated with SCA risk (adjusted incidence rate ratio per 1 °C increase: 0.94; 95% CI: 0.90-0.99), corresponding to a higher risk at lower temperatures. No statistically significant associations were observed between ambient air pollutants and SCA risk. CONCLUSIONS: In Japanese marathon races held predominantly in autumn and winter, lower ambient temperature at race start was associated with a higher risk of SCA, whereas no significant association was observed for ambient air pollutants.