Age-associated arterial wall thickening is related to elevations in sympathetic activity in healthy humans

Arterial wall hypertrophy occurs with age in humans and is a strong predict or of cardiovascular disease risk. The responsible mechanism is unknown, bu t data from studies in experimental animals suggest that elevated sympathet ic-adrenergic tone may be involved. To test this hypothesis in humans we st udied 11 young (29 +/- 1 yr; means +/- SE) and 13 older (63 +/- 1) healthy normotensive men under supine resting conditions. Muscle sympathetic nerve activity (MSNA) burst frequency (peroneal microneurography) was 70% higher in the older men (39 +/- 1 vs. 23 +/- 2 bursts/min; P < 0.001). Femoral art ery intima media thickness (IMT; B-mode ultrasound) and the femoral IMT-to- lumen diameter ratio (IMT/lumen) were similar to 75% greater in the older m en (both P < 0.001). Femoral IMT (r = 0.82) and the femoral IMT/lumen (r = 0.85) were strongly and positively related to MSNA (both P < 0.001). The si gnificant age group differences in femoral IMT and the IMT/lumen were aboli shed when the influence of MSNA was removed. In contrast, the relationship between MSNA and femoral wall thickness remained significant after removing the influence of age. We conclude that 1) primary aging is associated with femoral artery hypertrophy in humans and 2) this is strongly related to el evations in sympathetic nerve activity to the vasculature. These results su pport the hypothesis that tonic elevations in sympathetic nerve activity ma y be an important mechanism in the arterial remodeling that occurs with hum an aging.