When subjected to total body heating and exercise, skin blood flow doe
s not increase as much in elderly as in young subjects. It is not know
n whether this age-related decline is due to the autonomic dysfunction
that develops in the elderly or to changes at the level of the blood
vessels of the skin. We used local heating of the forearm to quantify
the intrinsic ability of the cutaneous vasculature to dilate in seven
young men (avg age 31 yr) and seven elderly men (avg age 71 yr). A wat
er spray was used to maintain a neutral skin temperature of 32-35 degr
ees C for > 10 min, followed by 60 min of a 42 degrees C skin temperat
ure to induce maximal skin blood flow. Forearm blood flow was measured
by venous occlusion plethysmography with a mercury-in-Silastic circum
ference gauge. At the neutral skin temperature, forearm blood flows in
the elderly subjects were comparable to those in the young subjects:
3.0 +/- 0.5 vs. 2.8 +/- 1.0 ml.min(-1).100 ml(-1). During the last 10
min of heating, however, blood flows were much lower in the elderly th
an in the young subjects: 11.1 +/- 2.7 vs. 19.9 +/- 5.2 ml.min(-1).100
ml(-1) (P = 0.002). We conclude that aging results in a reduction of
the maximal conductance of the cutaneous vasculature.