By Steven Reinberg
NEW YORK (Reuters Health) – The results of a randomized trial suggest that preterm infants exposed to cycled light experience faster weight gain compared with preterm infants exposed to near darkness.
Many neonatal units maintain near darkness to simulate the womb environment. "Constant bright light has been shown to be too stressful on preterm infants, causing irregular heart rates and decreased sleep," researchers from the Duke University School of Nursing explain in a press release.
"Probably, cycled light is a better light environment for preterm infants at some point, but it is not totally clear at what age," lead investigator Dr. Debra H. Brandon told Reuters Health.
Writing in the February issue of The Journal of Pediatrics, Dr. Brandon and her Durham, North Carolina-based associates describe the effects of cycled light on 62 infants born at less than 31 weeks of gestation.
The babies were randomly assigned to three groups: cycled light from birth, cycled light at 32 weeks postconceptual age, and cycled light at 36 weeks postconceptual age. "The kids who got the cycle light from birth had a mean gestational age of 28 weeks," Dr. Brandon noted.
"Cycled light establishes a day/night rhythm, mimicking the circadian rhythm cues that are established for full-term babies in the womb," Dr. Brandon said in a university statement. "Light is one method that we can use to promote circadian rhythms for these infants and encourage growth and healthy sleep patterns," she added.
Among the babies in the three groups, those who received cycled light from birth and from 32 weeks postconceptual age gained weight faster than those infants exposed to cycled light after 36 weeks postconceptual age, the investigators found. However, even those infants not exposed to cycled light until 36 weeks postconceptual age began to have accelerated growth after being exposed to cycled light, Dr. Brandon said.
"We still need to determine at what gestational age cycled light has the most benefit, because there may be some outcomes that are not positive from being exposed to cycled light," she said. For younger infants, the stress of cycled light exposure might outweigh any benefits that they would get from circadian rhythm development, Dr. Brandon added.
In the next phase of her research, Dr. Brandon plans to study the long-term outcomes of infants exposed to cycled light.
J Pediatr 2002;140:000-000.