COLD THERMOREGULATORY CHANGES INDUCED BY SLEEP-DEPRIVATION IN MEN

The aim of this study was to evaluate the thermoregulatory changes induced by 27-h of sleep deprivation (SD) in men at rest both in a comfortable ambient temperature and in cold air. A group of 12 male subjects were placed in a comfortable ambient temperature (dry bulb temperature, T-db=25 degrees C, relative humidity, rh=40%-50%, clothing insulation=1 do) for 1 h and then they were submitted to a standard cold air test in a climatic chamber for 2 h (T-db=1 degrees C, rh=40%-50%, wind speed =0.8 m.s(-1), nude), before and after 27 h of sleep deprivation. Thermoregulatory changes (rectal temperature, T-re; mean skin temperature, T-sk($) over bar; metabolic heat production M) were monitored continuously. At comfortable ambient temperature, no significant change was observed after SD for T-re, T-sk($) over bar and M. During the cold test, T-re did not change but T-sk($) over bar and M were higher after SD (P<0.05). Increased M (+6%, P<0.05) was related to earlier and higher shivering, with a possible increase in the sensitivity of the thermoregulatory system as shown by the Shorter time to onset of continous shivering (d): 8.66 (SEM 1.33) min versus 28.20 (SEM 1.33) min (P<0.001) and by a higher T-sk($) over bar observed at d: 27.60 (SEM 1.40)degrees C versus 21.40 (SEM 0.60)degrees C (P<0.001). These results were associated with higher cold sensations and shivering following SD. They also suggested that SD modified thermoregulatory responses at a central level especially in a cold environment.