Time-of-day difference of arterial stiffness between morning and afternoon in healthy young males

Abstract

Brachial-ankle pulse wave velocity (baPWV) is widely used as an index of arterial stiffness. Vascular function is believed to be influenced by the circadian rhythm; blood pressure gradually begins to rise after waking up, peaks during the day, and declines toward the night. However, the time-of-day difference in baPWV in healthy young men has not been fully clarified. Therefore, this study aimed to examine the differences in baPWV and hemodynamic parameters between morning and afternoon in healthy young men. A total of 20 healthy young men were recruited in this study. The participants were measured for baPWV, brachial and ankle blood pressure, and heart rate on the same day at 10:00 AM and 5:00 PM. A significantly lower baPWV was observed at 5:00 PM compared to 10:00 AM (p < 0.05). Similarly, brachial and ankle systolic blood pressure, diastolic blood pressure, and mean blood pressure were significantly lower at 5:00 PM compared to 10:00 AM (all p < 0.05). Pulse pressure and heart rate did not change significantly between the two time points. The present study demonstrated that baPWV showed a time-of-day difference and exhibited a lower velocity in the afternoon than morning in healthy young men, suggesting the importance of standardizing measurement timing in evaluating the effect of exercise interventions.