Cerebral pulsatility increases stress on the microvasculature of the brain causing damage. Age-related increases in arterial stiffness augment cerebral pulsatility via effects on large artery buffering capacity. Autonomic nervous system function also affect cerebral pulsatility by altering vascular tone. Physical activity (PA) may have a favorable effect on both vascular and autonomic function, and in turn, cerebral pulsatility. PURPOSE: 1) Determine the relationship between aortic stiffness and autonomic function with cerebral pulsatility index (PI) in young women. 2) Explore the role of PA as a potential correlate. METHODS: Eighty-two women (21±4 years) participated in this study. Moderate-to-vigorous physical activity (MVPA) was measured for 7 days using an accelerometer. Body composition was assessed using air displacement plethysmography. Middle cerebral artery PI was determined via transcranial Doppler. Aortic stiffness was measured via carotid-femoral pulse wave velocity (cf-PWV) using applanation tonometry. Autonomic function was assessed via heart rate variability (HRV). Low frequency (LF) power of HRV was used as a measure of sympathetic activity, while high frequency (HF) power of HRV was used as a measure of parasympathetic activity. RESULTS: PI was not significantly correlated with cf-PWV (r=-0.03, p=0.82) or lnHF (r=0.25, p=0.06). There was a significant, positive association between lnLF and PI (r=0.39, p=0.002). MVPA was not associated with cf-PWV (r=-0.18, p=0.13), lnLF (r=0.01, p=0.95) or PI (r=-0.04, p=0.79). CONCLUSION: Sympathetic activity is a more prominent correlate of cerebral pulsatility than large artery stiffness in young women. Sympathetic tone may increase vasoconstriction of the cerebral vasculature resulting in augmentation of cerebral pulsatility. Physical activity was not associated with vascular or autonomic correlates of cerebral pulsatility in young women.
Supported by NIH Grant 1R03MD011306-01A1