Effect of night and day on preterm infants in a newborn nursery: randomised trial. A controlled clinical trial of light and retinopathy of prematurity. Randomized controlled study of the effects of different durations of light exposure on weight gain by preterm infants in a neonatal intensive care unit. Circadian and sleep development in preterm infants occurs independently from the influences of environmental lighting. Preterm infants born at less than 31 weeks' gestation have improved growth in cycled light compared with continuous near darkness. Rest-activity patterns of premature infants are regulated by cycled lighting.
The effect of alternating night and day on sleep, feeding, and weight gain in 41 healthy preterm infants was examined in a randomised controlled trial. Twenty infants from a night and day nursery, where the intensity of light and noise was reduced between 7 pm and 7 am, spent longer sleeping and less time feeding and gained more weight than 21 infants from a control nursery, where the intensity of light and noise was not reduced. Differences were significant and became apparent only after discharge home; they were still present three months after the expected date of delivery, when infants from the night and day nursery were an average of 0.5 kg heavier (p less than 0.02). These findings suggest that physical environment has an effect (either direct or indirect) on the subsequent behaviour of preterm infants and that exposure to night and day is beneficial. Bright continuous light has been implicated in the pathogenesis of retinopathy of prematurity. To investigate the influence of light on the incidence and severity of retinopathy of prematurity, we enrolled 127 preterm infants (birth weight < or = 1,500 g; gestational age < or = 32 weeks) in a controlled clinical study. Randomization was done separately for three birth-weight groups (< 1,000 g; 1,000 to 1,249 g; 1,250 to 1,500 g). The babies' eyes were patched all day and night from birth to a gestational age of 35 weeks. The infants in the control group were exposed to cycled lighting conditions (that is, reduced light level during the night). Of 62 infants with patched eyes, 26 (42%) developed retinopathy of prematurity. In the control group, 25 of 65 infants (39%) showed retinopathy of prematurity (P = .596). There were also no statistically significant differences in the incidences of retinopathy of prematurity in the birth-weight subgroups or in the severity of retinopathy of prematurity. Thus, patching of the eyes from birth to 35 weeks of postconceptional age does not decrease the risk of retinopathy of prematurity in preterm infants when compared to a control group exposed to cycled lighting conditions. A randomized controlled study was carried out on 96 preterm infants (< 37 wk) with birthweight less than 2000 g admitted to a neonatal intensive care unit. The aim was to compare the weight gain between preterm infants exposed to 12 h cyclical lighting (intensity of light: 78.4 +/- 24.7 lux, mean +/- SD) and those exposed to a continuously dim environment (5.9 +/- 1.9 lux). The exclusion criteria were infants with major congenital malformations or who needed continuous lighting for treatment procedure and care. From day 7 of life until discharge, 50 infants were randomized to receive 12 h cyclical lighting and 46 infants to a continuously dim environment. There was no significant difference in the mean birthweight (12 h lighting vs continuously dim: 1482 vs 1465 g, p = 0.8), mean gestational age (31.6 vs 31.4 wk, p = 0.6), median duration of hospital stay (28.5 vs 28.5 d, p = 0.8), mean age to regain birthweight (13.0 vs 12.9 d, p = 0.3), mean weight gained by day 14 (27.6 vs 36.2 g, p = 1.0), median weight gain per day (11.9 vs 12.2 g, p = 0.9) or median body weight on discharge (1800 vs 1800 g, p = 0.4) between the two groups of infants.
                Exposing preterm infants to either 12 h cyglical lighting or continuously dim environment did not have any significant effect on their weight gain during the neonatal period. 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. Our purpose was to evaluate the benefits of cycled light (CL) versus near darkness (ND) on health in preterm infants born at <31 weeks' gestational age.
                Randomized, interventional study comparing infants receiving (1) CL from birth, (2) CL at 32 weeks' postconceptional age (PCA), and (3) CL at 36 weeks' PCA in transition for discharge home. Statistical significance was assessed with segmented mixed general linear models, analysis of covariance, general estimating equations, chi(2), and Fisher's exact procedure.
                Infants receiving CL at birth and 32 weeks' PCA gained weight faster than infants not receiving CL until 36 weeks' PCA. There were no differences among the groups in length of hospitalization stay or number of ventilator days, but the power was low for these variables.
                These findings suggest that CL has significant weight gain benefits over ND, and there are no short-term advantages of ND over cycled light for health in preterm infants. Many hospitalized premature infants are exposed to continuous dim lighting rather than to cycled lighting. However, we do not know whether dim lighting or low-intensity cycled lighting is more conducive to the development of rest-activity patterns that are in phase with the solar light-dark cycle. Thus, we examined the effects of nursery lighting conditions on the development of activity patterns in premature infants.
                Premature infants who were born at <32 weeks' postmenstrual age and were medically stable in neonatal intensive care unit rooms were randomly assigned between 32 and 34 weeks' postmenstrual age to either continuous dim lighting (<25 lux; duration 24 days; control group; n = 29) or cycled lighting (239 +/- 29 lux, 7:00 AM to 7:00 PM; <25 lux, 7:00 PM to 7:00 AM; duration: 25 days; experimental group; n = 33). Activity was continuously monitored from enrollment until approximately 1 month after discharge from the hospital. Weight and head circumference were also assessed up to 6 months after discharge from the hospital.
                Over the first 10 days at home, distinct day-night differences in activity were not seen in control subjects (D day-night: N 1.07 +/- 0.02), but experimental group infants were more active during the day than at night (day-night: 1.25 +/- 0.03). It was not until 21 to 30 days after discharge that day-night activity ratios in control infants matched those seen in experimental group infants shortly after discharge, yet even at this age, experimental group infants (day-night: 2.13 +/- 0.19) were considerably more active during the day than at night as compared with control subjects (day-night: 1.43 +/- 0.09).
                Exposure of premature infants to low-intensity cycled lighting in the hospital nursery induces distinct patterns of rest-activity that are apparent within 1 week after discharge. In comparison, the appearance of distinct patterns of rest and activity are delayed in infants who are exposed to continuous dim lighting in the hospital. These observations show that day-night rhythms in activity patterns can be detected shortly after discharge to home in premature infants and that the circadian clock of developing infants is entrained by cycled lighting.
Trials assessing the effect of CL have enrolled 469 infants. Trends for many outcomes favoured cycled light (CL) compared to near darkness (ND) and CL compared to continuous bright light (CBL) The studies may have lacked significance due to a lack of statistical power. Future research should focus on comparing CL to ND.