Effects of 29-h total sleep deprivation on local cold tolerance in humans

To study the effects of a 29-h total sleep deprivation (TSD) on local cold tolerance, 10 healthy men immersed their right hand for 30 min in a 5°C water bath (CWI) after a 30-min rest period in a thermoneutral environment (Control), after a normal night (NN) and after a 29-h TSD. CWI was followed by a 30-min passive rewarming (Recovery). Finger 2 and 4 skin temperatures (Tfi2, Tfi4) and finger 2 cutaneous vascular conductance (CVC) were monitored to study cold-induced vasodilation (CIVD). Rectal temperature (Tre), mean skin temperature ([Formula: see text]), heart rate (HR) and blood pressure (BP) were also measured. Blood samples were collected at the end of the Control, at the lower and at the first maximal Tfi2 values during CWI and at Recovery. Tfi2, Tfi4 and CVC did not differ after TSD at Control, whereas they were reduced during CWI (-2.6 ± 0.7°C for Tfi2; -2 ± 0.8°C for Tfi4, -79 ± 25% for relative CVC, P < 0.05) as during Recovery (-4.9 ± 1.9°C for Tfi2, -2.6 ± 1.8°C for Tfi4, -70 ± 22% for relative CVC, P < 0.05). After TSD, the lower CVC values appeared earlier during CWI (-59 ± 19.6 s, P < 0.05). After TSD at Control and CWI, plasma endothelin levels were higher and negatively correlated with Tfi2, Tfi4 and CVC. However, no effect of TSD was found on the number and amplitude of CIVD and in Tre, HR, BP and catecholamines, for all periods. We concluded that TSD induced thermal and vascular changes in the hand which impair the local cold tolerance, suggesting that TSD increases the risk of local cold injuries.