Comparative analysis of circadian rhythms of hemodynamics and physical activity

In determining the time structure (circadian rhythm) of blood pressure (BP), heart rate (HR), and physical activity (actigraphy indicators ZCM, HPIM) in everyday life and how they are related, 20 clinically healthy participants, 26.7 ± 2.3 years of age, were examined. Phase-weighted averages obtained by the population-mean cosinor detected statistically significant 24- and 12-h components (P < 0.001). The cross-correlation function between physical activity and BP shows a strong common circadian variation. The similarity of the circadian waveform of cardiovascular variables and activity, gauged by the ratio of the amplitudes of the 12-h and 24-h components, is statistically confirmed by their positive correlation. The best correspondence between fluctuations in hemodynamics and actigraphy data is shown for systolic BP and ZCM. Our results indicate the synchronicity of the circadian rhythms of BP, HR rate and physical activity, supporting the statement that the circadian rhythm of BP is not a sole direct response to the circadian rhythm of physical activity. At the same time, physical activity has a positive effect on the circadian system of the whole organism, through the central pacemaker, and thus indirectly affects the cardiovascular circadian rhythms.