Although body-warming with hot spa-bathing has been proposed to exert medical therapeutic effects on certain diseases, whether body-warming has preventive and promotive effects remains unknown. To clarify this issue, an epidemiological questionnaire study regarding personal hot spa-bathing habits and disease history was carried out in Japan, where individuals engage in daily warm water bathing. Questionnaires regarding hot spa-bathing habits and disease history were randomly sent to 20,000 residents aged ≥65 years living in Beppu, a city in Japan that has the highest concentration of hot spa sources in the world. The results showed that habitual hot spa-bathing exerts preventive or promotive effects on the occurrence of certain diseases, such as hypertension (preventive) and collagen disease (promotive) in women, and cardiovascular diseases (preventive) and colon cancer survival (promotive) in men. These findings suggest that habitual body warming is an effective and economical method with beneficial preventive and promotive effects on various diseases. Does habitual body-warming lead to any beneficial medical effects in humans? Although this is a simple question, little remains known about the effects of systemic-heating on the human body, including whether habitual body warming is beneficial or harmful for health. In Western countries, body-warming activities are not habitual, although there are numerous hot spa resorts in Europe, where balneotherapy is covered by national health insurance as medical treatment; however, the duration of balneotherapy is limited to within several weeks. Therefore, the biological effects of long-term balneotherapy remain unknown. In addition, balneotherapy is only prescribed for patients, not for healthy people.In Japan, people have a long history of habitual daily bathing that involves warm water bathing as opposed to showering. They typically use warm water from their own homes for bathing, but in hot springs areas, which are prevalent in regions all over Japan, people prefer to take habitual hot spa baths, which contain rich minerals. Compared with home bathing, hot spa-bathing in water rich in minerals that foster heat-conduction is more effective for raising core body temperature. The Japanese Ministry of the Environment has published a list of the balneotherapeutic effects of spa-bathing with respect to hot spa type 1 . According to a list of minerals found in hot spas between 1978 and 2014, spa water quality can be categorized in to 11 distinct types. This list shows the association between each spa type and its target diseases. However, the prophylactic effect of spa-bathing remains unknown. Kyushu University Beppu Hospital is located in Beppu city, which contains the world highest concentration of hot spa sources. This area has nine of the 11 spa types. Thus, Beppu city is one of best areas to conduct epidemiological studies about the disease preventive effects of habitual hot spa-bathing. Therefore, we conducted an epidemiological questionnaire study on elderly resident...