Advancing Age Is Associated with Augmented Venoarteriolar Response to Leg Dependency

Abstract

BackgroundThe venoarteriolar response (VAR) is a non‐baroreflex mediated regional vasoconstriction mechanism which has been proposed to contribute to about 45% of the increase in total peripheral resistance during orthostasis. Advancing age is related to elevated total peripheral resistance and it is involved in the pathogenesis of hypertension. However, whether advancing age is associated with an enhanced VAR is not known.ObjectiveTo test the hypothesis that there are sex and age differences in the VAR among healthy individuals.Method18 (10 women) young (mean±SD; 28±4 years) and 22 (11 women) older (72±4 years) healthy normotensive adults participated in the study. Brachial and femoral artery diameter and blood flow velocity were measured using doppler ultrasound. Forearm and calf cutaneous blood flow were measured using laser‐doppler flowmetry. Assessments were performed while the arm and leg were in the horizontal position and repeated following limb dependency (35–40 cm below the heart level) for 5 min. Blood pressure (BP, SunTech) and heart rate (HR, electrocardiogram) were also measured. The percent reduction in vascular conductance (=blood flow/mean BP) during limb dependency was used to assess the VAR.ResultsThe VAR was not different between dominant and non‐dominant limbs. The VAR was more pronounced in the leg compared with the arm (24+/−7% vs. 18+/−5%; P=0.04) while it was not different between men and women. Older subjects had a greater VAR in the leg compared with their younger counterparts (29+/−8% vs. 21+/5%; P=0.04), but the VAR in the arm did not differ between the groups (17+/−6 vs. 19+/−4%, young vs. old; P=0.80). Cutaneous VAR showed similar results as those measured by doppler ultrasound. BP and HR remained unchanged prior to and during limb dependency.ConclusionAging is associated with augmented venoarteriolar response in the leg but not in the arm. The enhanced venoarteriolar response induced vasoconstriction may contribute importantly to hypertension in the older population.