Effects of Age and Sex on Middle Cerebral Artery Blood Velocity and Flow Pulsatility Index Across the Adult Lifespan

Abstract

Reduced middle cerebral artery blood velocity (MCAv) and flow pulsatility are contributors to age-related cerebrovascular disease pathogenesis. It is unknown whether the rate of changes in MCAv and flow pulsatility support the hypothesis of sex specific trajectories with aging. Therefore, we sought to characterize the rate of changes in MCAv and flow pulsatility across the adult lifespan in females and males as well as within specified age ranges. Participant characteristics, mean arterial pressure, end-tidal carbon dioxide, unilateral MCAv and flow pulsatility index (PI) were determined from study records compiled from three institutional sites. 524 participants (18-90 years; 319 females; 205 males) were included in the analysis. MCAv was significantly higher in females within the 2nd (p <0.001), 5th (p = 0.01), and 6th (p <0.01) decades of life. Flow PI was significantly higher in females within the 2nd decade of life (p <0.01). Rate of MCAv decline was significantly greater in females than males (-0.39 vs. -0.26 cm s-1·yr, p = 0.04). Rate of flow PI rise was significantly greater in females than males (0.006 vs. 0.003 flow PI, p = 0.01). Rate of MCAv change was significantly greater in females than males in the 6th decade of life (-1.44 vs. 0.13 cm s-1·yr), p = 0.04). These findings indicate that sex significantly contributes to age-related differences in both MCAv and flow PI. Therefore, further investigation into cerebrovascular function within and between sexes is warranted to improve our understanding of the reported sex differences in cerebrovascular disease prevalence.