Advances of human core temperature minimum and maximal paradoxical sleep propensity by ambient thermal transients

By using slow thermal transients of reduced amplitude (+/-3 degrees C) around 29 degrees C (thermoneutrality in humans sleeping nude) during only 1 night (experimental, EX), we have advanced the minimum of rectal temperature (T-re) and the peak of their paradoxical sleep propensity (PPSP) of sleeping subjects. During this EX night, T-re minimum was significantly (P = 0.0001) advanced by 143 min versus that observed during baseline night spent at thermoneutrality. The advance of PPSP was objectivated by the more rapid cumulation of paradoxical sleep (P = 0.02) during the second half of EX night, i.e. strictly after the occurrence (around 0330 h) of the new T-re minimum, and by the earlier occurrence of its barycentric point (P = 0.04) between 0330 and 0700 h. The involvement of the central thermoregulatory system on phase-shifting mechanisms is discussed.