Age-related changes in cerebral hemodynamics and their correlations with cardiac autonomic functions

Objectives: This study was designed to evaluate the correlations between cerebral hemodynamics and cardiac autonomic functions in aging process using transfer function techniques. Methods: Arterial blood pressure (ABP), middle cerebral artery flow velocity (MCAFV) detected by transcranial Doppler sonography and electrocardiogram were recorded simultaneously in 20 young (27.5 +/- 0.9 years) and 20 middle-old-aged (54.3 +/- 1.5 years) healthy volunteers. Variability of ABP, MCAFV and heart rate (HR) were diffracted into very low (VLF, 0.016 - 0.04 Hz), low (LF, 0.04 - 0.15 Hz) and high frequency (HF, 0.15 - 0.4 Hz) components. Cerebral vasomotor reserve was quantified by specific ABP - MCAFV transfer function measurements. Results: The young group had significantly higher LF transfer phase and HF transfer magnitudes of ABP - MCAFV transfer function; higher HF powers of HR variability; and higher baroreflex sensitivity than those of the middle-old-aged group. LF phase and HF magnitude of ABP - MCAFV transfer function were positively correlated with HF powers of HR variability. Discussion: Although aging process is not obviously associated with changes in the static values of ABP, MCAFV and HR in this study, it is accompanied by significant declines in cerebral vasomotor reserve, cardiac vagal activity and baroreflex sensitivity. Besides, age-related changes in cerebral vasomotor reserve are positively related to those in cardiac vagal activity.