PS-BPR02-10: SYMPATHETIC NERVE TONE AND THE INDOOR ENVIRONMENT IN A HIGHLY INSULATED AND AIRTIGHT MODEL HOUSE DURING THE COLD WINTER SEASON

Abstract

While evidence for lifestyle modification such as salt reduction, weight loss, exercise, sobriety, and smoking cessation has accumulated for perfect blood pressure control, there is a lack of evidence on blood pressure fluctuations due to housing environments such as thermal protection and heating. In particular, blood pressure fluctuation due to the difference in room temperature between the living room and the dressing room, toilet, and bedroom is known to be a major risk during the winter season. Therefore, this study focused on the autonomic nervous system as one of the factors causing blood pressure fluctuations, and compared the fluctuations when the same subjects spent two days each at home and in a highly insulated, airtight model house. JOURNAL/jhype/04.03/00004872-202301001-00877/figure1/v/2023-10-24T163949Z/r/image-jpeg Subjects were 6 males and 5 females with 20–70 years old. Autonomic activity was measured and calculated using portable electrocardiography (Heartnote: JSR corporation, Tokyo) for the 8 subjects for whom it was possible to measure heart rate, CVRR (Coefficient of variation of R-R interval) and LF(low frequency)/HF(high frequency) ratio. An sympathetic hyperactivation was defined to show more than +2SD for distribution within an individual in LF/HF calculated every 10 seconds. The salivary amylase was measured at several times per day. The indoor environment temperatures were recorded by installing data loggers equipped with temperature sensors in various rooms and taking continuous measurements at 10-min intervals. In the model house, room temperatures were kept constant at 18°C or more. However, in the home, there were large temperature differences between rooms, and in one case, a room temperature in the bedroom was recorded at 6.3°C. In the overall analysis of heart rate and CVRR, there were large individual differences in both absolute values and diurnal variations, and no obvious differences by housing environment. In a detailed analysis focusing on early morning (2 hours after waking), two subjects showed excessive sympathetic activation in the early morning at home, but not in the model house. There was no correlation between this change and salivary amylase. In terms of sleep quality, there were no differences by housing environment. This case of early morning sympathetic activation in a residential setting suggests the importance of the residential setting in the management of early morning hypertension.