Effects of indoor temperature and its fluctuation on blood pressure and its variability.

Cardiovascular diseases (CVDs) are the number one health threat globally. Adverse indoor thermal environments are associated with excess mortality caused by CVDs in the cold season. While many studies have focused on the impact of indoor temperature on CVDs, none has considered the fluctuation of indoor temperature. To quantify the effect of indoor temperature on blood pressure and the effect of indoor temperature fluctuation on blood pressure variability (BPV), 172 middle-aged and elderly people in areas that experience both hot summers and cold winters in China completed a household survey regarding their characteristics and living habits. A hierarchical linear model (HLM) was used to analyze the impact of indoor temperature on home blood pressure. A multiple linear model was used to analyze the effect of indoor temperature fluctuation on day-to-day home blood pressure variability. The results showed that there was a significant negative correlation between morning temperature below 18 °C and blood pressure, especially systolic blood pressure (SBP). At the same time, morning temperature fluctuations have an independent influence on BPV, and a deviation of morning temperature fluctuation greater than 1.1 °C significantly increased BPV. Morning temperature and its fluctuation threshold for the rise of SBP and its variability of middle-aged and elderly people were clarified, which can provide a basis for the design, operation, and evaluation of residential thermal environmental health performance for the middle-aged and elderly population in this area, thereby reducing the cardiovascular health risk of the corresponding population.