Attenuated peripheral vasoconstriction during an orthostatic challenge in older men

BACKGROUND: orthostatic hypotension is common in older men and associated with morbidity and mortality. During orthostatic challenges, older men maintain their blood pressure by an augmented increase in total peripheral resistance. Changes in the leg vascular bed contribute importantly to blood pressure regulation during orthostatic challenges, partly because of blood pooling in the legs. Little is known about the contribution of the leg vascular bed to the augmented increase in total peripheral resistance. OBJECTIVE: to examine tilt-induced peripheral vasoconstriction in the leg vascular bed of young and older men. METHODS: we measured forearm and calf blood flow in 12 young and 12 older men, using venous occlusion plethysmography during 30 degrees head-up tilt (HUT). Forearm and calf vascular resistance were calculated as mean arterial blood pressure divided by blood flow. RESULTS: during HUT, calf and forearm vascular resistance increased in older and young men. The increase in forearm vascular resistance was similar between older (40 +/- 6%) and young men (51 +/- 12%). However, the increase in calf vascular resistance was lower in older (96 +/- 15%) than in young men (175 +/- 30%). CONCLUSION: advancing age leads to an attenuated tilt-induced increase in calf vascular resistance, which may contribute to age-related orthostatic hypotension.