Dynamic cerebral autoregulation is unaffected by aging

Background and Purpose-Normal aging is associated with marked changes in th e cardiovascular and cerebrovascular systems. Although cerebral autoregulat ion (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 sy stolic blood pressure (BP), underwent measurement of cerebral blood flow ve locity by transcranial Doppler ultrasound and noninvasive beat-to-beat arte rial BP measurement during induced and spontaneous dynamic BP stimuli. A st andard dynamic autoregulatory index (ARI) was derived for each spontaneous and induced dynamic BP stimulus to include the step response, as well as ca rdiac baroreceptor sensitivity (BRS), for the 2 groups. Results-The mean age of the young group was 29+/-5 years, and that of the o lder 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 diff erences were demonstrated in step response plots or in ART values for any p resser 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 cardia c BRS, dynamic CA, as assessed by step response analysis as well as cerebra l blood flow responses to transient and induced BP stimuli, is unaffected b y aging.