Seasonal Variation in Home Blood Pressure Measurements and Relation to Outside Temperature in Japan

Abstract

Previous studies have suggested that outside temperature affects blood pressure (BP) levels. However, recently, due to a spreading heating system, the seasonal variation in BP levels might be smaller, especially in colder seasons when more heat is used. We used continuous measurements of home BP data to track seasonal variations of BP to analyze the relation between outside temperature and BP values. Among 213 volunteers who were asked to measure BP in September 2000, 79 participants (mean age 72.7 years, 60.0% women) measured BP at least once per month until August 2003 (36 months). The mean number of measurements was 19.0 times/month. Information on outside temperature was provided by the Japan Meteorological Agency. We used general linear models to analyze the relation between outside temperature and BP values. Blood pressure levels were lowest in the warmest months. However, the highest BP levels were not observed in the coldest month, but rather in March. A clear inverse association between temperature and BP values was evident only in periods when outside temperatures were above 10°C. When the outside temperature was ≥ 10°C, 1°C increment of outside temperature correspond to 0.40 and 0.28 mmHg decrease of systolic blood pressure (SBP) and diastolic blood pressure (DBP), whereas the corresponding values were 0.06 and 0.01 mmHg when the outside temperature was <10°C. In conclusion, inverse association between outside temperature and BP was observed only in warmer seasons.

• seasonal variation
• home blood pressure
• outside temperature
• observational studies
• population

ACKNOWLEDGMENTS

The authors would like to express their appreciation to all staff in Nishiaizu town who participated in the study. The authors are also grateful to Y. Nakata, M. Wagatsuma, H. Okajima, and T Muroi for their helpful secretarial assistance.

This study was done as part of a Nishiaizu town enterprise called “Kenko Jumyo Enshin Jigyo” (Enterprise for prolonging healthy life expectancies). This study was also supported by a Grant-in-Aid for challenging Exploratory Research (21659162) from the Ministry of Education, Culture, Sports, Science and Technology, Japan.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the papers.