Impact of indoor temperature instability on diurnal and day-by-day variability of home blood pressure in winter: a nationwide Smart Wellness Housing survey in Japan

Wataru Umishio,Hiroshi Yoshino,Tanji Hoshi,Takesumi Yoshimura,Shintaro Ando,Masaru Suzuki,Yoshihisa Fujino,Kazuomi Kario,Toshiharu Ikaga,Shuzo Murakami

doi:10.1038/s41440-021-00699-x

Abstract

Home blood pressure (HBP) variability is an important factor for cardiovascular events. While several studies have examined the effects of individual attributes and lifestyle factors on reducing HBP variability, the effects of living environment remain unknown. We hypothesized that a stable home thermal environment contributes to reducing HBP variability. We conducted an epidemiological survey on HBP and indoor temperature in 3785 participants (2162 households) planning to have their houses retrofitted with insulation. HBP was measured twice in the morning and evening for 2 weeks in winter. Indoor temperature was recorded with each HBP observation. We calculated the morning-evening (ME) difference as an index of diurnal variability and the standard deviation (SD), coefficient of variation (CV), average real variability (ARV) and variability independent of the mean (VIM) as indices of day-by-day variability. The association between BP variability and temperature instability was analyzed using multiple linear regression models. The mean ME difference in indoor/outdoor temperature (a decrease in temperature overnight) was 3.2/1.5 °C, and the mean SD of indoor/outdoor temperature was 1.6/2.5 °C. Linear regression analyses showed that the ME difference in indoor temperature was closely correlated with the ME difference in systolic BP (0.85 mmHg/°C, p < 0.001). The SD of indoor temperature was also associated with the SD of systolic BP (0.61 mmHg/°C, p < 0.001). The CV, ARV, and VIM showed similar trends as the SD of BP. In contrast, outdoor temperature instability was not associated with either diurnal or day-by-day HBP variability. Therefore, residents should keep the indoor temperature stable to reduce BP variability.

Highlights

Home blood pressure monitoring (HBPM) is currently one of the standard methods used in the diagnosis and Kitakyushu, Fukuoka, Japan 9 Tohoku University, Sendai, Miyagi, Japan 10 Institute for Building Environment and Energy Conservation, Kojimachi, Chiyoda-ku, Tokyo, JapanImpact of indoor temperature instability on diurnal and day-by-day variability of home blood pressure. . .management of hypertension
HBPM is useful for assessing a wide range of BP variabilities, including diurnal variability, as indicated by morning-evening difference (ME difference), and day-by-day variability, as indicated by the standard deviation (SD), coefficient of variation (CV), average real variability (ARV), and variability independent of the mean (VIM) measurements
We investigated the association between home BP (HBP) variability and indoor temperature instability based on the results of the baseline survey

Summary

Introduction

Impact of indoor temperature instability on diurnal and day-by-day variability of home blood pressure. Previous studies have revealed a strong association between home BP (HBP) level and cardiovascular disease (CVD) events [5, 6]. HBPM is useful for assessing a wide range of BP variabilities, including diurnal variability, as indicated by morning-evening difference (ME difference), and day-by-day variability, as indicated by the standard deviation (SD), coefficient of variation (CV), average real variability (ARV), and variability independent of the mean (VIM) measurements. Several studies have indicated that there are additional benefits to reducing the ME difference [8] and day-by-day variability indices described above [9, 10], independent of HBP level. Reducing HBP variability is valuable for preventing CVD events

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Results

Conclusion