Circadian and sleep development in preterm infants occurs independently from the influences of environmental lighting

This study investigated the effect of intermediate nursery illumination on circadian rhythm and sleep development of preterm infants. Preterm infants were randomly assigned to one of two intermediate nursery rooms: a dimly lighted room, the dim (control) group, or a day-night lighted room, the cycled (intervention) group. Continuous rectal temperature and sleep were recorded at 36 wk postconceptional age (before discharge) and at 1 and 3 mo corrected age at home. Forty infants, 21 in the dim group and 19 in the cycled group, were recorded. The clinical demographic data and neonatal scores were similar between groups before the intervention. Circadian rhythms and sleep showed significant development with age, but there was no environmental lighting effect. Circadian and sleep organization seems to develop endogenously in preterm infants.