[Background] Sudden deaths in the bathroom (bath-related deaths) in Japan are increasing due to the aging society, but the pathophysiological mechanism responsible for this increase has not been elucidated. Thus, it is important to establish bath-related death prevention awareness. In response to this need, we investigated the efficacy of an alert for bathing safety, “Alerting information when bathing” in reducing bath-related deaths.

  [Method] Statistical analyses were conducted on 1,133 cases of bath-related death that occurred during winter among inquests performed by the Kagoshima Prefectural Police between 2006 and 2019. Kagoshima Prefecture was divided by prefectural police jurisdiction, and ambient temperatures with a high frequency of bath-related deaths in each area were identified and issued as “Alerting information when bathing” through various media from November 2023 to February 2024. We compared the number of fatalities before and after issuance of the alert to determine whether the alert affected the number of bath-related deaths. In addition, we analyzed the results of a questionnaire on our website (HP) and LINE application (app) to evaluate the degree of penetration of the alert system.

  [Results and Discussion] The total number of bath-related deaths did not decrease significantly after issuance of the alert, but the number and percentage of fatalities among those <60 years old decreased significantly. During the time that the alert was available, 80% of the respondents to the website survey conducted were in their <70 years old, and 76.7% of the respondents who registered as friends on the LINE app were also <70 years old.

  [Conclusion] Our results suggest that alerting information can reduce bath-related deaths on a range of age groups. However, 90% of the bath-related deaths occurred among those aged ≥65 years, so future work is needed to publicize the information to those aged >70 years.

  【Purpose】Sauna bathing has been reported to be associated with reduced cardiovascular mortality. Conversely, it has been suggested that cold-water bathing may negatively affect the cardiovascular system, such as by acutely increasing systolic blood pressure. This study investigated the effects of alternating contrast bathing, a fusion of sauna and cold-water bathing, on the cardiovascular system, employing arterial stiffness as a key index.

  【Method】The participants included 11 healthy young men (21.3±0.6 years) who were divided into the sauna bathing group (10 min of sauna bathing, 1 min of showering, 5 min of rest; 3 sets) or the contrast bathing group (10 min of sauna bathing, 1 min of cold-water bathing, 5 min of rest; 3 sets). A cross-over test was conducted. To eliminate dehydration effects, each participant ingested 500 mL of water from immediately before through during the bathing protocol. Arterial stiffness, an index of the cardiovascular system, was evaluated using brachial-ankle pulse wave velocity (baPWV). BaPWV was measured pre-bathing, immediately after bathing, and 30 min after bathing. The bathing temperature settings were 86°C for the sauna, 40°C for the shower, and 17°C for the cold bath. Statistical analysis was performed using a two-way analysis of variance (ANOVA) with bathing method (contrast bath, sauna) and time (before bathing, immediately after bathing, 30 min after bathing) as factors.

  【Result】Two-factor analysis of variance on bathing method and time course in relation to baPWV results revealed no interaction between bathing method and time course. However, a main effect was observed in the factor of time course (p＝0.038), and a significant decrease was observed at 30 min after bathing compared with pre-bathing (p＝0.034).

  【Conclusion】In healthy young men hydrated with 500 mL of fluid, both sauna bathing and contrast bathing significantly reduced arterial stiffness, with no significant difference between them. Future research should assess these effects in diverse populations, accounting for bathing protocols and participants’ age and health.