Meteorological and Environmental Factors Associated with Sudden Cardiac Arrest during Marathons in Japan

Background Sudden cardiac arrest (SCA) during marathons is a rare but critical event. While underlying cardiovascular conditions have been linked to SCA, the role of environmental factors, such as ambient air quality and meteorological conditions, remains unclear. We conducted a nationwide study in Japan to examine the association between meteorological and air pollution variables and the occurrence of SCA during marathons. Data from approximately 4.53 million runners participating in full marathons certified by the Japan Association of Athletics Federations from April 2011 to March 2020 were analyzed. SCA cases were linked to meteorological variables (temperature, humidity, solar radiation, wind speed, precipitation, and air pressure) and air pollutants (particulate matter and gaseous pollutants). Results Among 4.53 million runners, 74 SCA cases were identified. Poisson regression analysis showed that lower ambient temperatures at race start were significantly associated with increased SCA risk (adjusted incidence risk ratio per 1°C decrease: 1.06; 95% confidence interval: 1.02–1.12). No significant associations were found between air pollutants and SCA risk. Conclusions Lower temperatures at the start of marathons were associated with a higher risk of SCA, while no significant correlation was observed with air pollutants. These findings suggest that temperature may be an important environmental factor influencing the risk of SCA during marathons.