A review of Japanese-style bathing: its demerits and merits

Abstract Japanese-style bathing (JSB), which involves soaking in hot water up to the shoulders in deep bathtubs for a long time in the evening to night, is unique. Many experimental and epidemiological studies and surveys have shown that JSB improve sleep quality, especially shortens sleep onset latency in winter. In addition, repeated JSB lead the improvement of depressive symptoms. JSB is a simple and low-cost non-pharmacological measure to sleep difficulty in winter and mental disorders, especially for the elderly. On the contrary, drowning, while soaking in a bathtub, is the most common of accidental death at home in Japan. It is estimated that approximately 19,000 Japanese individuals die annually while taking a bath, mostly during winter, and most victims are elderly people. Elderly Japanese people tend to prefer a higher-risk JSB because the temperature inside the house during winter, especially the dressing room/bathroom temperature, is very low. Since the physiological thermal effect of the elderly associated with bathing is relatively lower among the elderly than the young, the elderly prefer to take a long hot bath. This elderly’s favorite style of JSB results in larger increased blood pressure in dressing rooms and larger decreased in blood pressure during hot bathing. A sudden drop in blood pressure while immersed in the bathtub leads to fainting and drowning. Furthermore, elderly people are less sensitive to cold air or hot water, therefore, it is difficult to take appropriate measures to prevent large fluctuations in blood pressure. To ensure a safe and comfortable winter bathing, the dressing room/bathroom temperature needs to be maintained at 20 °C or higher, and several degrees higher would be recommended for the elderly.