Assessment of the Effects of Aerobic Fitness on Cerebrovascular Function in Young Adults Using Multiple Inversion Time Arterial Spin Labeling MRI

Abstract

This cross-sectional study investigated the effects of aerobic fitness on cerebrovascular function in the healthy brain. Gray matter cerebral blood flow (CBF) and cerebrovascular reactivity (CVR) were quantified in a sample of young adults within a normal fitness range. Based on existing Transcranial Doppler ultrasound and fMRI evidence, we predicted a positive relationship between fitness and resting gray matter CBF and CVR. Exploratory hypotheses that higher $\stackrel{.}{V}$ O₂peak would be associated with higher GM volume and cognitive performance were also investigated. 20 adults underwent a $\stackrel{.}{V}$ O₂peak test and a battery of cognitive tests. All subjects also underwent an MRI scan where multiple inversion time (MTI) pulsed arterial spin labeling (PASL) was used to quantify resting CBF and CVR to 5% CO₂. Region of interest analysis showed a non-significant inverse correlation between whole-brain gray matter CBF and $\stackrel{.}{V}$ O₂peak; r = -0.4, p = 0.08, corrected p (p') = 0.16 and a significant positive correlation between $\stackrel{.}{V}$ O₂peak and whole-brain averaged gray matter CVR; r = 0.62, p = 0.003, p' = 0.006. Voxel-wise analysis revealed a significant inverse association between $\stackrel{.}{V}$ O₂peak and resting CBF in the left and right thalamus, brainstem, right lateral occipital cortex, left intra-calcarine cortex and cerebellum. The results of this study suggest that aerobic fitness is associated with lower baseline CBF and greater CVR in young adults.

Keywords: arterial spin labeling; cerebral blood flow; cerebral hemodynamics; cerebrovascular reactivity; exercise.