Aging Progressively Impairs Endothelium-Dependent Vasodilation in Forearm Resistance Vessels of Humans

Studies in experimental models suggest that endothelium-derived nitric oxide is reduced with aging, and this circumstance may be relevant to atherogenesis. The aim of this study was to determine whether increasing age resulted in altered endothelium-dependent vasodilation in the forearm resistance vessels of healthy humans. Forearm blood flow was measured in 119 healthy subjects, aged 19 to 69 years, by venous occlusion plethysmography. Brachial artery infusions of methacholine chloride (0.03 to 10.0 microgram/min) were used to assess endothelium-dependent vasodilation and of sodium nitroprusside (0.03 to 10.0 microgram/min) to assess endothelium-independent vasodilation. The slope of the dose-blood flow response relation was calculated in each subject for each drug. Univariate and multiple stepwise regression analyses were used to relate vascular reactivity to selected variables, including age, lipids, and blood pressure. Endothelium-dependent vasodilation was progressively impaired with increasing age, assessed as a reduction in slope from 2.25 +/- 0.16 to 0.34 +/- 0.11 (mL/100 mL tissue per minute)/(microgram/min) (P <.001). The decline in endothelium-dependent vasodilation was already evident by the fourth decade (age 30 to 39 years). Endothelium-independent vasodilation did not change with age. Age, total cholesterol, and low-density lipoprotein cholesterol were univariate predictors of endothelium-dependent vasodilation. Age remained the most significant predictor of endothelium-dependent vasodilator responses by multiple stepwise regression analysis. From these observations, it can be concluded that endothelium-dependent vasodilation declines steadily with increasing age in healthy human subjects. Age is a strong univariate and multivariate predictor of endothelium-dependent vasodilation. This finding may be a marker for more widespread endothelial dysfunction.