Very preterm infants show earlier emergence of 24-hour sleep-wake rhythms compared to term infants.

BACKGROUND: Previous studies show contradictory results about the emergence of 24-h rhythms and the influence of external time cues on sleep-wake behavior in preterm compared to term infants. AIMS: To examine whether very preterm infants (<32 weeks of gestational age) differ in their emergence of the 24-h sleep-wake rhythm at 5, 11 and 25 weeks corrected age compared to term infants and whether cycled light conditions during neonatal intermediate care affects postnatal 24-h sleep-wake rhythms in preterm infants. STUDY DESIGN: Prospective cohort study with nested interventional trial. SUBJECTS: 34 preterm and 14 control term infants were studied. During neonatal hospitalization, preterm infants were randomly assigned to cycled light [7 am-7 pm lights on, 7 pm-7 am lights off, n=17] or dim light condition [lights off whenever the child is asleep, n=17]. OUTCOME MEASURES: Sleep and activity behavior recorded by parental diary and actigraphy at 5, 11 and 25 weeks corrected age. RESULTS: Sleep at nighttime and the longest consolidated sleep period between 12 pm-6 am was longer (mixed model analysis, factor group: p=0.02, resp. p=0.01) and activity at nighttime was lower (p=0.005) at all ages in preterm compared to term infants. Cycled light exposed preterm infants showed the longest nighttime sleep duration. Dim light exposed preterm infants were the least active. CONCLUSIONS: Preterm infants show an earlier emergence of the 24-h sleep-wake rhythm compared to term infants. Thus, the length of exposure to external time cues such as light may be important for the maturation of infant sleep-wake rhythms. Trial registry number: This trial has been registered at www.clinicaltrials.gov (identifier NCT01513226).

Cycled light exposure reduces fussing and crying in very preterm infants.

OBJECTIVE: To examine whether cycled lighting (CL) conditions during neonatal care in very preterm infants (<32 weeks' gestational age [GA]) decrease crying and fussing behavior, improve the consolidation of sleep, and influence activity behavior at 5 and 11 weeks' postterm corrected age (CA) compared with preterm infants cared for in dim lighting (DL) conditions. METHODS: Thirty-seven preterm infants were randomly assigned to CL (7 am-7 pm lights on, 7 pm-7 am lights off [n = 17; mean GA: 30.6 ± 0.95 weeks; 9 girls]) or DL (lights off whenever the child is asleep [n = 20; GA: 29.5 ± 2.1 weeks; 8 girls]) conditions. Sleeping, crying, and activity behavior was recorded by using parental diaries and actigraphy at 5 and 11 weeks' CA. RESULTS: A significant reduction of fussing (59.4 minutes/24 hours [± 25.8 minutes]) and crying (31.2 minutes/24 hours [± 14.4 minutes]) behavior and a trend to higher motor activity during daytime was found in CL-exposed infants at 5 and 11 weeks' CA compared with infants cared for in DL conditions. No significant difference between groups was observed for sleep behavior at 5 and 11 weeks' CA. Infants in CL conditions showed a trend to improved daily weight gain (average: 3.6 g/d) during neonatal care compared with DL conditions. CONCLUSIONS: CL conditions in neonatal care have beneficial effects on infant's fussing and crying behavior and growth in the first weeks of life. This study supports the introduction of CL care in clinical neonatal practice.