Aging is associated with a diminished axon reflex response to local heating on the gaiter skin area

Abstract

Objectives: Elderly patients are susceptible to skin ulcerations on the supramedial malleolar area of the leg. Our aim was, using local thermal hyperemia, to study microvascular function on the gaiter skin area of elderly, but otherwise healthy volunteers, because abnormal microvascular reactivity could contribute to ulcerations in this region.

Methods: Two groups of healthy volunteers were enrolled according to age, including 20 subjects aged from 18 to 30 years (young group) and 42 subjects aged from 60 to 86 years (older group). Local thermal hyperemia to 43°C was performed for 1 h using heating circular probes and skin blood flow was recorded using Laser Doppler Imaging, with or without 2 h lidocaine/prilocaine cream application. Sodium nitroprusside iontophoresis was also performed.

Results: The initial local thermal hyperemia peak was lower in the older group (14.7 mV/mmHg±6.9) compared to the young group (19.9±7.2, P=0.009). Lidocaine/prilocaine cream decreased the initial local thermal hyperemia peak and the late plateau for all groups. The local thermal hyperemia plateau and sodium nitroprusside iontophoresis corrected for skin resistance did not differ between older and younger subjects.

Conclusions: Physiological aging is associated with an altered initial axon reflex response to local heating in the supramedial malleolar skin. Further work is required to determine whether these changes are more pronounced in frail and dependent groups and whether they could explain the higher incidence of skin ulcerations in the supramedial malleolar skin associated with venous insufficiency and neuropathy.