The Association between Tub-Bathing Frequency and the Incidence of Depressive Symptoms among Older People in Japan: JAGES Longitudinal Study

Abstract

[Background]

Depression is one of major causes of functional decline among older people. In this prospective longitudinal study, we aimed to investigate the association between tub-bathing frequency and the incidence of depressive symptoms among older people in Japan.

[Methods]

We recruited 4,466 participants (2,159 men and 2,307 women), who completed both 2010 and 2013 questionnaires of the Japan Gerontological Evaluation Study, be independent in activities of daily living, and not depressed in 2010, which was defined as Geriatric Depression Scale (GDS) <5. We classed tub-bathing frequency in 2010 as 0-6 times/week and 7 or more times/week in summer and winter, respectively. Participants were observed the incidence of depressive symptoms (GDS >=5) in 2013. We estimated the incidence rate ratios of depressive symptoms according to the tub-bathing frequency separately in summer and winter by using the Poisson regression analysis adjusting for 7 potential confounders: age, sex, marital status, employment status, equivalized income, years of education, and treatment for any disease.

[Results]

After adjustment for potential confounders, the incidence rate ratios (95% confidence interval) of the participants bathing 7 or more times/week compared with those bathing 0-6 times/week were 0.84 (0.71-1.00) for summer, and 0.77 (0.65-0.91) for winter.

[Discussion]

Our main finding was that participants who took baths more frequently were less likely to be depressed after 3 years. Therefore, tub-bathing might be beneficial for older people’s mental health.