Objective Bath-related sudden cardiac arrests occur frequently in Japan. Although previous studies have reported that most fatal events occurr in winter, the reason why such events exhibit a seasonal variation has not been elucidated. In this study, we hypothesized that the occurrence of bath-related deaths was correlated with a low air temperature. Methods This prospective cross-sectional observational study was conducted in the Tokyo Metropolitan area between October 2012 and March 2013. Data were collected for all cases involving the activation of the emergency medical system because of an accident or acute illness related to bathing that occurred in Tokyo during the study period. In particular, elderly (≥65 years) cardiac arrest victims who had been found in a bathtub filled with water were enrolled. The relationship between the daily number of cardiac arrest events and the lowest daily air temperature in Tokyo was studied using a nonlinear regression model. Results A total of 3,624 bath-related events were registered in this study. Among these events, 1,081 deaths of elderly individuals who had been found in a bathtub filled with water were recorded. A close correlation was observed between the daily number of events and the lowest daily air temperature. This correlation was described by the following equation: y=8.38e-0.07x, where y was the daily number of cardiac arrests and x was the lowest daily air temperature. Conclusion A low air temperature was closely correlated with the occurrence of bath-related cardiac arrest.
Keywords: aging; cardiac arrest; cold environment; mortality; prevention; weather.