Variation of night-time infant body temperature associated with diurnal rhythm and sleep state

Aim: To document diurnal and sleep state modulation of body temperature during early infancy. Design: 5 infants were prospectively studied overnight each month, when aged from 1 to 5 months, sleeping supine in a thermally controlled laboratory. Multiple body temperatures and full polysomnography were recorded. Temperature change was determined by subtracting the value at the end from that at the beginning of individual active/quiet sleep periods. Results: During active sleep mean rectal temperature increased by O.O5”C, abdominal by O.O8”C, forehead by 0.12”C and during quiet sleep there were equivalent mean falls of - O.O7”C, - O.ll”C and - 0.25”C. Larger mean rises were seen during nocturnal awakenings in rectal temperature O.ll”C, P less than 0.0001. During the first period of quiet sleep there were larger mean falls compared to periods of quiet sleep later in the night, Rectal - 0.31”C P less than O.OOOl, Forehead - 0.63”C P = 0.0013. However during the first period of Active Sleep mean rectal and forehead temperatures fell rather than rose, - 0.13”C P less than 0.0001, - 0.08”C P = 0.024, respectively. Rectal and forehead temperatures began to fall prior to sleep whereas shin and abdominal temperature rose during this period. The only age related trends were for greater falls of rectal temperature in the first period of active or quiet sleep. There were less consistent patterns of shin temperature with sleep state. Conclusions: There is a reciprocal relationship between rectal and some peripheral temperatures during sleep with characteristic changes with sleep state. These patterns are affected by undertying diurnal rhythms which change with ag