Age-associated changes in cardiovagal baroreflex sensitivity are related to central arterial compliance.

Cardiovagal baroreflex sensitivity (BRS) declines with advancing age in humans, but the underlying mechanism has not been established. Using two different approaches, we determined the relation between age-associated decline in cardiovagal BRS and the compliance of an artery in which arterial baroreceptors are located. First, we measured carotid artery compliance (via the simultaneous application of ultrasonography and arterial applanation tonometry) and cardiovagal BRS (phase IV of the Valsalva maneuver) in 47 healthy sedentary men that varied widely in age (19--76 yr). Cardiovagal BRS declined progressively with age (r = -0.69; P < or = 0.001) and was positively related to carotid artery compliance (r = 0.71; P < or = 0.001). Stepwise multiple-regression analysis revealed that carotid artery compliance was the strongest independent physiological correlate of cardiovagal BRS and that it explained 51% of the total variance. Second, we studied 13 middle-aged and older previously sedentary men (age 56 +/- 2 yr) before and after 13 wk of aerobic exercise intervention. Regular exercise increased both cardiovagal BRS and carotid artery compliance (P < 0.05) and the two events were strongly and positively related (r = 0.72; P < 0.01). We conclude that reduced carotid artery compliance may play an important mechanistic role in age-associated decrease in cardiovagal BRS in healthy sedentary humans.