Transepidermal water loss during sleep in infants.

Transepidermal water evaporation rate (ER) was measured in 207 infants with a mean postnatal age of 12.7 +/- 10.6 weeks. Measurements were made from the forehead with the use of an Evaporimeter during polygraphic sleep recordings performed under standard conditions. ER values were computed in g/m2 X h. Evaporation rates were significantly lower during rapid eye movement (REM) sleep (8.5 +/- 4.4 g/m2 X h), compared to values measured during quiet wakefulness (11.6 +/- 7.4) or non-REM (NREM) sleep (11.2 +/- 7.6). The differences were not related to age, sex, weight, or rectal temperature, as shown by a covariance analysis. These data, recorded in normal infants, indicate the need to consider the state of sleep or wakefulness of the subjects when comparing results of water evaporation studies.