Association between outdoor temperature and bath-related drowning deaths in Japan (1995-2020): modifying factors and the role of prefectural characteristics.
- Author:
Yoshiaki TAI
1
;
Kenji OBAYASHI
1
;
Yuki YAMAGAMI
1
;
Keigo SAEKI
1
Author Information
- Publication Type:Journal Article
- Keywords: Accidental drowning; Bath-related deaths; Housing insulation; Older population; Outdoor temperature
- MeSH: Japan/epidemiology*; Humans; Drowning/epidemiology*; Male; Aged; Female; Baths/statistics & numerical data*; Middle Aged; Temperature; Aged, 80 and over; Adult; Young Adult; Risk Factors; Adolescent
- From:Environmental Health and Preventive Medicine 2025;30():55-55
- CountryJapan
- Language:English
-
Abstract:
BACKGROUND:Older adults in Japan have the highest drowning mortality rate globally due to frequent bathing practices. Low outdoor temperatures have been linked to bath-related deaths; however, previous studies employed limited statistical models and focused on a single prefecture. Given Japan's aging population, preventing bath-related deaths is a public health priority. This study aimed to analyze the association between outdoor temperature and bath-related drowning deaths across Japan from 1995 to 2020 (n = 110,938), examining regional variations and identifying contributing prefectural characteristics.
METHODS:Daily counts of bath-related drowning deaths per prefecture were matched with daily mean temperature data from the Japan Meteorological Agency. Prefecture-level demographic and environmental data were obtained from Japan's Official Statistics. We applied a generalized additive mixed model to examine the association between daily mean temperature and bath-related drowning death risk. Meta-regression was used to identify prefecture-level modifiers.
RESULTS:Bath-related drowning death risk peaked at a daily mean temperature of 1.8 °C (relative risk [RR] 9.7, 95% confidence interval [CI]: 9.5-9.9), compared with the lowest risk at 30.3 °C. The association was stronger at mid-range temperatures, particularly among males and individuals aged ≥65 years. Among prefectures, Kagoshima-the southernmost prefecture on Japan's main islands-had the highest maximum RR at 19.6 (95% CI: 16.2-23.6), while Hokkaido-the northernmost prefecture-had the lowest at 3.8 (95% CI: 3.4-4.3). Prefecture-level factors that strengthened this relationship included a lower prevalence of double-pane windows as a proxy of housing insulation and higher annual mean temperatures with ratio of RR change per one standard deviation increase of 0.76 (95% CI: 0.69-0.83) and 1.27 (95% CI: 1.18-1.37), respectively.
CONCLUSIONS:Warmer prefectures in southern regions exhibited greater maximum-to-minimum risk ratios compared to cooler northern prefectures. This paradoxical finding underscores the importance of region-specific interventions to reduce bath-related deaths.
