Effect of age on cutaneous vasomotor responses during local skin heating

This study examined the effect of ageing on the low-frequency oscillations (vasomotion) of skin blood flow in response to local heating (LH). Skin blood flow was assessed by laser-Doppler flowmetry on the forearm at rest (33 °C) and in response to LH of the skin to both 42 °C and 44 °C in 14 young (24 ± 1 years) and 14 older (64 ± 1 years) participants. Vasomotion was analyzed using a wavelet transform to investigate power of the frequency intervals associated with endothelial, neural, myogenic, respiratory, and cardiac activities of the laser-Doppler signal. Laser-Doppler flux increased in both groups with LH (both d > 1.8, p <0.001). Endothelial activity increased in both groups following LH to 42 °C (young d = 1.4, p <0.001; older d = 1.2, p = 0.005) and 44 °C (young d = 1.4, p = 0.001; older d = 1.5, p = 0.005). Endothelial activity was higher in the young compared to older group during LH to 42 °C (d = 1.4, p = 0.017) and 44 °C (d = 1.5, p = 0.004). In response to LH to 42 °C and 44 °C, neural activity in both groups was decreased (both groups and conditions: d > 1.2, p <0.001). Myogenic activity increased in the younger group following LH to 44 °C (d = 1, p = 0.042), while in the older group, myogenic activity increased following LH to 42 °C (d = 1.2, p = 0.041) and 44 °C (d = 1.1, p = 0.041). Respiratory and cardiac activities increased in both groups during LH to 42 °C and 44 °C (All: d > 0.9, p <0.017). There were no differences in wavelet amplitude between younger and older in the neural (d = 0.1, p > 0.7), myogenic (d = 0.3, p > 0.7), respiratory (d = 0.4, p > 0.6), and cardiac (d = 0.1, p > 0.7) frequency intervals. These data indicate that LH increases cutaneous endothelial and myogenic activity, while decreasing neural activity. Furthermore, ageing reduces the increase in cutaneous endothelial activity in response to LH.