Overnight central and peripheral temperature changes in normal infants.

Aim: To explore the relationship between central and peripheral temperature in normal infants after being put down to sleep.

Methods: Overnight shin and rectal temperatures of 21 normal infants were continuously recorded at home for three nights at 2 wk, 6 wk, 3 mo and 5 mo of age. Parents documented the start and end of feed/nappy changes during the night.

Results: An initial fall in rectal temperature was recorded on 149 out of 161 nights. This was linearly correlated with a rise in shin temperature for 106/149 (71%) nights (median R2 = 0.95, lower quartile 0.92, upper quartile 0.97). It was not possible to rule out a change in thermal insulation over the shins as a confounding variable in this strong association. However, a similar inverse relationship was seen between shin and rectal temperature during 111 of 121 (92%) feed/nappy changes.

Conclusion: The fall in rectal temperature after being put down to sleep may be due to redistribution of heat rather than decreased production or heat loss. If causal, the development in early infancy of an inverse relationship between shin and rectal temperature may be important for cardiovascular homeostasis. Further sleep laboratory work is required to distinguish peripheral temperature changes on falling asleep from those associated with changes in thermal insulation.