Interaction Between Body Temperatures and the Direction of Sleep Stage Transition in Neonates
Véronique Bach, Frédéric Telliez, André Leke*, Carlo Chiorri**, Jean-Pierre Libert
URAPC, Faculté de Médecine, Amiens, France, *Pédiatrie II, CHU Amiens Nord, Amiens, France,
**Instituto di Psichologia, Firenze, Italy

A cool environment increases active sleep (AS) of neonates at the expense of quiet sleep (QS). With regard to the interaction between thermoregulation and sleep, the aim of this study was to determine whether the levels and patterns of body temperatures differ between AS and QS, and according to the outcome of an AS episode (QS or wakefulness). This has never been studied in neonates. Thirty-seven neonates were exposed to a thermoneutral and a cool environment. Esophageal, mean skin temperature and oxygen consumption (Vo₂) were scored during AS and QS episodes and at the sleep stage transitions (n=475). Analyses of variance were performed. The outcome of AS (complete cycle AS QS; incomplete cycle AS wakefulness [W]) was considered. In the cool environment, AS and incomplete cycles increased whereas QS decreased. There was no difference in the optimum range of body temperatures at which QS or wakefulness occurred after an AS episode. QS and AS episodes differed according to the magnitude and time patterns of body temperatures and Vo₂. Throughout QS, a progressive decline of Vo₂ and of body temperatures was found. The fall in Vo₂ commenced during the preceding episode of AS. Our results also suggest that in neonates exposed to a cool environment, thermoregulation prevails over the need to conserve energy since QS decreases and W increases.