Age- and sex-related differences in sudomotor function evaluated by the quantitative sudomotor axon reflex test (QSART) in healthy humans.

The aim of the present study was to quantitatively investigate the age and sex-related differences in sudomotor function in healthy humans. The quantitative sudomotor axon reflex test (QSART) with iontophoresis (2 mA for 5 min) and 10% acetylcholine (ACh) was performed to determine axon reflex-mediated (AXR), with and without iotophoresis (AXR(1) and AXR(2), respectively), and directly activated (DIR) sweating. All experiments were conducted under thermoneutral conditions (temperature 24.0 ± 0.5°C; relative humidity 40 ± 3%). In general, men had enhanced values of onset time of AXR, sweat rates, activated sweat gland density (SGD) and activated sweat gland output (SGO) than women, but not in all cases. The onset time of AXR (r(2)  = 0.567; P < 0.001) was positively correlated with advancing age, whereas sweat rates of AXR(1) and AXR(2) (r(2)  = 0.571 and r(2)  = 0.486, respectively; P < 0.0001), DIR (r(2)  = 0.594; P < 0.0001), SGD (r(2)  = 0.496; P < 0.0001) and SGO (r(2)  = 0.551; P < 0.0001) were negatively correlated in both men and women with advancing age. The results demonstrate that an attenuation of sudomotor function occurs with aging in both sexes. Moreover, the findings showed a progressive increase in onset time and a decrease in sweat rates, SGD and SGO with increasing age in both sexes. A variation in sweat function was found between sexes, but not in all age groups.