ASSOCIATION BETWEEN INDOOR THERMAL ENVIRONMENT OF RESIDENTIAL BUILDINGS AND CEREBROVASCULAR DISEASE: Indoor thermal environment during winter and home blood pressure of elderly persons in rural areas of Yamagata Prefecture

According to statistical data published by the Japanese government, the major causes of death in Japanese people are cancer, heart disease and cerebrovascular disease. The incidence of cerebrovascular disease in particular trends to be higher during winter than summer. One possible reason for this seasonal difference is that exposure to low temperatures can cause fluctuations in blood pressure. In houses with poor thermal insulation, indoor temperature differences between heated and non-heated spaces, such as the bathroom, corridors, and lavatory, can be considerable in winter. Many houses in the Tohoku region have a poor thermal environment in winter, and the incidence of cerebrovascular disease in this area is the highest in Japan. Hasegawa and Yoshino investigated the association between the indoor thermal environments of houses in Yamagata Prefecture, which is located in the Tohoku region, and the death rate due to cerebrovascular disease in the winter of 1983 and 1984. They found marked temperature differences between heated living rooms and unheated rooms. In addition, the occupants of houses with unheated lavatories and/or bedrooms were significantly more susceptible to cerebral vascular accidents. In order to clarify the association between the indoor environment of residential buildings and cerebrovascular disease, an epidemiological survey was therefore conducted in Yamagata Prefecture. The areas investigated included three of the rural towns that were surveyed in the study conducted approximately 30 years ago. The study was divided into three phases. The first phase (Phase 1) comprised a cross-sectional questionnaire on the indoor thermal environment and occupants' lifestyle habits, and was administered to 188 elderly persons. The second (Phase 2) and final (Phase 3) phases comprised field measurements of the indoor thermal environments and home blood pressure measurements of subjects selected from the Phase 1 part of the study, respectively. This study describes the results obtained from indoor temperature and blood pressure measurements of 55 elderly persons over an approximately 18-month period in the study area. The association between blood pressure and indoor temperature exposure in these elderly persons is analyzed statistically. In almost the houses surveyed, the living room temperature was maintained at approximately 18℃ after dinner. However, once the heater was turned off, the room temperature decreased rapidly overnight and approach