Arterial wave reflection and vascular autonomic modulation in young and older men

Background and aims: Arterial stiffening with aging causes early return of reflected arterial pressure waves from peripheral arteries and augmentation of these waves on incident aortic pressure waves. The purpose of this study was to examine the relationship between pressure wave reflection and augmentation from peripheral arteries and peripheral sympathetic vasomotion in young and older men. Methods: Thirty males (15 young, 15 older) participated in this cross-sectional study. Radial artery applanation tonometry was used to derive aortic pressure wave reflection time (Δt; index of aortic stiffness) and augmentation index (AIx; index of wave reflection intensity). Low frequency (LF) power attained from spectral decomposition of beat-to-beat systolic blood pressure (SBP_LF) variability was used as an estimate of sympathetic vasomotor modulation. Results: SBP_LF power was higher in older vs younger men (8.0±0.9 vs 4.5±0.5 mmHg², p<0.05). Older men had higher AIx (24.0±1.8% vs -11.6±2.3%, p<0.05) and lower Δt (138.1±1.9 ms vs 185.8±5.9 ms, p<0.05) compared with younger males. When ANCOVA was performed with SBP_LF power as the covariate, the group differences in AIx₇₅ and Δt were preserved. Results from multiple regression revealed that, after entering age into the model, SBP_LF power was not a significant correlate of AIx or Δt, accounting for a non-significant 1.2% and 1.1% of the variance, respectively. Conclusions: These findings suggest that increased blood pressure variability with aging is not related to age-associated increases in aortic stiffness or wave reflection.