Effects of night-time bedroom temperature on morning blood pressure during winter: A multilevel analysis

Purpose / Context – To analyse the association between night-time temperature in the bedroom and morning blood pressure (BP). Methodology / Approach - Data were obtained from field surveys conducted from November 2014 to March 2015 on indoor temperature, home BP, sleep, and personal attributes. One hundred and twelve participants (73 households) were classified into three groups by the window glazing and the presence or absence of a solar floor heating system in their homes. Group 1 was single glazing and no solar floor heating system. Group 2 was double glazing and no solar floor heating system. Group 3 was double glazing and a solar floor heating system. Results – The night-time temperature in the bedroom and morning temperature in the living room in Group 3 were higher than those of Groups 1 and 2. After adjusting for personal factors, a 1°C decrease of night-time temperature was significantly associated with a 0.61 mmHg increase of morning systolic blood pressure (SBP) in Group 1, and a 0.92 mmHg increase of morning SBP in Group 2. The temperature in Group 3 did not show a significant association with morning SBP. Key Findings / Implications – There was no effect on morning BP when the night-time temperature was over 18°C, whereas on mornings below 18°C SBP increased as the temperature decreased. Originality - The findings of this study may help improve indoor thermal environments to control hypertension and prevent cardiovascular disease, and thus reduce the medical costs associated with cardiovascular disease