Multivariate analysis of the rise in home blood pressure by personal factors: A field survey on the effect of indoor thermal environment on blood pressure in winter

Japan is confronted with the problems of an aging population, and government finances are severely strained by rising expenditures on medical and nursing care. It is expected that medical and nursing care expenses reached 45 trillion yen in 2010, and such expenses are expected to double to 92 trillion yen by 2025. An effective measure for lowering such expenditures is the prevention of cardiovascular disease, a major cause of which is hypertension. Recently, the effects of the indoor thermal environment on blood pressure have attracted attention. However, these effects have not been studied in relation to personal factors, particularly individual attributes and lifestyle. Therefore, the purpose of this research is to analyze the relation between indoor temperature and blood pressure while taking into account personal factors. Field surveys on home blood pressure, indoor temperature, and personal factors were conducted in winter 2012 and 2013. Controlling for personal factors, systolic blood pressure increased by 4.3 mmHg per 10 °C decrease in indoor air temperature. Also, a 1 °C decrease in indoor air temperature increased 1.1-fold the likelihood of a value above 135 mmHg (baseline for systolic blood pressure at home). Furthermore, the effect of indoor air temperature was stronger in residents with more severe arteriosclerosis.