Dynamic cerebral autoregulation is unaffected by aging

Background and Purpose-Normal aging is associated with marked changes in the cardiovascular and cerebrovascular systems. Although cerebral autoregulation (CA) is impaired in certain disease states, the effect of age per se on dynamic CA in humans is unknown and the focus of this study. Methods-Twenty-seven young subjects (less than or equal to 40 years) and 27 older subjects (greater than or equal to 55 years), matched for sex and systolic blood pressure (BP), underwent measurement of cerebral blood flow velocity by transcranial Doppler ultrasound and noninvasive beat-to-beat arterial BP measurement during induced and spontaneous dynamic BP stimuli. A standard dynamic autoregulatory index (ARI) was derived for each spontaneous and induced dynamic BP stimulus to include the step response, as well as cardiac baroreceptor sensitivity (BRS), for the 2 groups. Results-The mean age of the young group was 29+/-5 years, and that of the older group was 68+/-5 years. Cardiac BRS was reduced in the older group (8.6+/-4.5 versus 16.9+/-8.8 ms/mm Hg; P<0.0001). However, no age-related differences were demonstrated in step response plots or in ART values for any presser or depressor dynamic BP stimulus (P=0.62), with mean ARI values for all stimuli combined being 4.9+/-1.8 for the young group and 5.0+/-2.3 for the older group. Conclusions-Although increasing age is associated with a decrease in cardiac BRS, dynamic CA, as assessed by step response analysis as well as cerebral blood flow responses to transient and induced BP stimuli, is unaffected by aging.