Immediate Effects of Phototherapy on Sleep of Very Preterm Neonates: An Observational Study

Aim: Sleep in mature and premature babies is important for physical and mental regeneration and brain development. Process C (internal clock) and process S (sleep wake homeostasis) are the basis of sleep–wake regulation. Light exposure is one of the strongest factors influencing the synchronization of the sleep–wake processes. In the case of hyperbilirubinemia, premature babies undergo phototherapy (blue-green light) at least 12 hours in succession and are exposed to permanent light. Little is known about the influence of light on the ultradian rhythm of premature babies. The hypothesis of the study was that the ultradian rhythm is perturbated and that wake phases are longer during phototherapy compared with the phases without.

Methods: We included 24 very preterm and/or very low birth weight infants born less than 32 weeks of gestational age (GA) or < 1,500 g birth weight. Video recordings were taken for 3 hours on each of the subject's first 5 days of life. On the basis of breathing patterns, eye and body movements, behavioral states were defined as being awake (W), in active sleep (AS), or quiet sleep (QS). We compared videos with and without phototherapy in a multilevel univariable regression analysis for amounts of QS and active states (W + AS). We considered birth weight, GA, postnatal age, and type of ventilation as possible predictors.

Results: No significant associations between phototherapy and the amounts of QS (p = 0.726) and active behavioral states (p = 0.274) were found. As a secondary result, we did find a significant increase in time spent awake in correlation with increasing GA (p = 0.002; R2 = 21%).

Conclusion: Our data suggest that phototherapy does not influence sleep regulation in very premature infants during their phases with phototherapy compared with or without in their first days after birth. Ultradian rhythm seems neither to be influenced by blue-green light nor by the absence of light changes: Premature babies seem to be mainly driven by their internal clock. In agreement with earlier studies, we found an increase in wake time in infants with a higher GA, possibly as an effect of brain maturation.

Keywords: preterm infants, phototherapy, video analysis, sleep states.