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

ObjectiveBrachial-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, 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. MethodsA total of 20 healthy young men were recruited in this study.The participants were measured baPWV, brachial and ankle blood pressure, and heart rate on the same day at 10:00 AM and 5:00 PM. ResultsA 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. ConclusionThe present study demonstrated that baPWV shows time-of-day difference and exhibited lowers in the afternoon than morning in healthy young men, suggesting an importance of standardization of measurement timing in evaluating the effect of sports science and exercise intervention studies.