Circadian pattern and night-day variations in human arterial stiffness: assessment using ambulatory recording of arterial pressure and pulse transit time

Several factors have been implicated in the circadian pattern of cardiovascular vulnerability. However, the exact mechanisms involved in the peak incidence of cardiovascular events occurring during the early morning hours and in the afternoon are not completely identified. Arterial stiffness (AS) is a risk factor for cardiovascular morbidity and mortality. The purpose of our study was to investigate the circadian variation of AS in healthy individuals and to test the hypothesis that there was a circadian pattern in the AS coincident with the circadian variation in the cardiovascular susceptibility. Additionally, a night-daytime comparison of AS was performed. Method: 24-hrs of ambulatory blood pressure, heart rate and aortic-brachial pulse transit time (PTTAB) recordings were obtained in sixteen healthy individuals. AS surrogates, derived from the PTTAB and systolic and diastolic pressure were calculated. The myocardial oxygen consumption (MVO2) was quantified. The AS and MVO2 shows a circadian pattern with the highest and lowest levels, respectively, in the night. The greater reductions in the AS were temporally coincident with the morning increase in the arterial pressure, heart rate, and MVO2. The lesser AS found during the day-time, could be considered a physiological adaptation to minimize the oxygen consumption during the period of maximal physical activity.