Age-related attenuation of conduit artery blood flow response to passive heating differs between the arm and leg

Little is known about why the attenuation of heat loss responses with aging begins in the lower limbs. This study sought to determine whether passive heating causes the age-related decrease and limb-specific difference of blood flow (BF) responses between conduit brachial and femoral arteries, which are related to differences of cutaneous vascular conductance (CVC) between the upper and lower limbs.

In 15 older and 12 younger males, BF in the brachial and femoral arteries was ultrasonically measured and CVC in the forearm and thigh was assessed during lower leg immersion in hot water at 42 °C (ambient temperature: 30 °C, relative humidity: 45%) for 40 min.

The increased BF of brachial artery at the end of passive heating was similar between both age groups (older: 140 ± 4%; younger: 146 ± 11%), while that of femoral artery was smaller in older than younger group (119 ± 4% vs. 166 ± 11%, P < 0.01). Moreover, the increased CVC in the forearm was similar between the age groups (older: 356 ± 50%; younger: 308 ± 46%), although CVC in the thigh was significantly lower in older than younger group (303 ± 33% vs. 427 ± 51%, P < 0.05). These results corresponded to the BF responses of the brachial and femoral arteries, respectively.

These results indicate that age-related decrease and limb-specific difference occur also in conduit arteries of arm and leg, which might be related to the different reduction in CVC between forearm and thigh.