Age‐related alterations in the critical closing pressure of the cerebral circulation from rest to exercise in healthy humans

Abstract

We sought to examine the influence of age on exercise‐induced changes in cerebral vascular tone. The critical closing pressure (CCP), or pressure at which cerebral blood flow ceases, was estimated by linear extrapolation from arterial blood pressure (ABP) and middle cerebral artery blood velocity (MCAV) waveforms at rest and during moderate intensity steady‐state cycling at 50% heart rate reserve in 12 young (24±1 yr) and 12 older middle‐aged (57±2 yr) healthy subjects. No age‐group differences were observed in end‐tidal PCO2 at rest or during exercise (P=0.181). The increases in ABP during exercise were greater in older subjects (P<0.001), while changes in mean MCAV from rest were similar between groups (P=0.395). Importantly, the CCP was significantly elevated in both young (Δ +12.1 mmHg, P=0.005) and older (Δ +21.4 mmHg, P<0.001) subjects during exercise. Moreover, this change in CCP from rest was significantly greater in the older subjects (P=0.025). These data suggest that compared to younger subjects, older subject's exhibit larger exercise‐induced increases in cerebral vascular tone. We speculate that the greater increases in CCP may serve to protect the blood‐brain barrier from the higher blood pressure responses evoked by dynamic exercise in older subjects.Supported by R01‐HL093167.