The relationship between home blood pressure measurement and room temperature in a Japanese general population

Blood pressure (BP) is influenced by various factors, and it is known that temperature and BP have a negative relationship. However, few reports have examined the relationship between BP and temperature throughout the day in the same participant over time. Therefore, this study aimed to investigate the relationship between BP and temperature in the morning and evening in the same participants during a time period of ~1 year. In total, 401 participants, who participated in a community-based health checkup survey in Tarumizu, Japan, were enrolled. Five participants were excluded due to missing data. All participants measured their BP and the room temperature at home using a blood pressure monitor (HEM-9700T, OMRON Healthcare, Kyoto, Japan). The mean systolic BP (SBP) and diastolic BP (DBP) in the morning were significantly higher than the mean of the measurements taken in the evening (SBP: morning vs. evening 128 ± 15 mmHg vs. 122 ± 14 mmHg, P < 0.0001; DBP: morning vs. evening 77 ± 10 mmHg vs. 72 ± 8 mmHg, P < 0.0001). Using a linear mixed model with participants as a random effect, SBP and DBP were significantly associated with temperature in both the morning and evening. In the morning, in almost every month except July, a significant association between SBP and temperature was observed. However, there was a significant relationship between evening BP and temperature in all months. In conclusion, BP was significantly related to temperature in both the morning and evening during the year-long study. Furthermore, BP and temperature were significantly associated in all months except morning measurements in July.