Frequency of Bathtub Bathing and Developing Dementia in Community-Dwelling Older Adults in Japan: A 9-Year Follow-Up in JAGES Cohort Study
- VernacularTitle:日本の地域在住高齢者における浴槽入浴頻度と認知症発症の関連：JAGESコホートデータによる9年間追跡研究
- Author:
Natsuyo YANAGI
1
;
Shinya HAYASAKA
2
;
Katsunori KONDO
1
;
Toshiyuki OJIMA
3
Author Information
- Keywords: tub bathing; dementia; older adults; cohort study
- From:The Journal of The Japanese Society of Balneology, Climatology and Physical Medicine 2025;88(2):73-82
- CountryJapan
- Language:Japanese
- Abstract: Background: In recent years, Finnish sauna bathing has been reported to have beneficial health effects, such as reducing the risk of hypertension and dementia. Although tub bathing in Japan, which is used daily by the Japanese, differs from sauna bathing, there are a few reports on its potential effects in reducing the risk of cardiovascular disease and depressive symptoms, but no reports on dementia. Therefore, we aimed to investigate the association between bathing and incident dementia in Japanese community-dwelling older people using large longitudinal data. Methods and Results: We used data from the Japan Gerontological Evaluation Study (JAGES), which included community-dwelling older people aged ≥65 years who were not certified for long-term care. The baseline survey was conducted in 2010, and the onset of dementia was assessed using records from Japan’s long-term care insurance system. After excluding respondents with missing data on bathing frequency in summer and winter separately, a total of 7,509 individuals were analysed for summer and 7,590 for winter. Bathing frequency was divided into two groups: low frequency (0-6 times/week) and high frequency (≥7 times/week). To examine the association between bathing frequency and incident dementia, we performed survival analysis using the competing risk model and calculated sub hazard ratios (SHRs) and 95% confidence intervals (CIs). During 9 years of follow-up, 1,430 (17.2%) cases of dementia were identified in 8,317 individuals. In the crude model, the high-frequency bathing group showed a significantly lower risk of incident dementia, and this association remained significant after full adjustment, with SHRs of 0.74 (95% CI: 0.62-0.88) in summer and 0.82 (95% CI: 0.70-0.97) in winter. Conclusions: High-frequency bathing was associated with a lower risk of incident dementia among Japanese community-dwelling older adults. This finding suggests that tub bathing, one of the lifestyle habits of older people in Japan, may contribute to preventing dementia.
