The influence of cold temperatures on the progression of hypertension: an epidemiological study

In order to clarify the relationship between cold temperatures and the progression of hypertension, a prospective epidemiological study was carried out in a cold area of Hokkaido, Japan. We analysed the findings in 909 subjects, who were followed up for 8 years (1977 to 1985). The difference between the mean blood pressure in winter and in summer in the first year was significantly and positively correlated with the difference between the mean blood pressure in the first and in the eighth year. The winter/summer difference was significantly higher in the group with progressive hypertension than in the other groups. The pressor response to exposure to cold was significantly greater in hypertensives, and tended to be higher in borderline hypertensives compared with normotensives. From these results, we conclude that a cold environment might increase the inhabitants' blood pressure levels, and the difference between a subject's blood pressure in winter and summer may predict future hypertension.