Response to Yatabe et al.

Abstract

We thank Dr Yatabe et al.1 for their interest in our subanalysis of the Hypertension Objective Treatment based on Measurement by Electrical Devices of Blood Pressure (HOMED-BP) study regarding seasonal variations in home blood pressure.2 As they indicated,1 the lack of data on room temperature, which would affect home blood pressure on each occasion, was a limitation of the HOMED-BP study. Because the addresses of study patients were not collected, we instead used regional information from study centers for the analysis of summer–winter differences in the home blood pressure, that is, northern or southern part of Japan.2 The incorporation of an automated thermometer (a temperature data logger) into the blood pressure measurement device1 seems be an innovative approach for home monitoring, as few studies investigating seasonal variation have focused on room temperature.3 However, some studies have evaluated the association between outdoor temperature and blood pressure,4, 5 and our report2 regarding overall trends in seasonal variations in blood pressure supports their findings that the outdoor temperature is highly correlated with the blood pressure in a population.4, 5 Surprisingly, just as in HOMED-BP, a slight shift in the timing of seasonal variations in blood pressure to a few weeks earlier than the nadir and peak of outdoor temperature was also observed among the participants in Aizumisato town in which the room temperature instead of the outdoor temperature was assessed.1