Robustness of Basal Heart Rate against Declining Physical Activity Analysis of Physiological Big Data

To examine the influences of reduced physical activity on the circadian architecture of heart rate, we performed big data analysis on the effect of relative time spent in the lying position on the timing and level of basal heart rate (BHR, 24-h minimum heart rate). In the big data of simultaneously recorded 24-h electrocardiogram and triaxial acceleration in 12,530 men and 17,529 women, BHR was found to occur at the median [IQR] of 04:07 [01:35- 05:35] in men and 03:50 [01:35-05:53] in women. The clock time when BHR occurred was slightly accelerated by advancing age (-11 and -8 min per 10-y increment of age for men and women) and was slightly delayed by increasing lying time (only +6 and +9 min per 10% increment of lying ratio in the day). This study indicates that BHR is a robust biological property that is not easily lost by declining physical activity.