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Published on: October 24, 2019
Rest-activity patterns of premature infants are regulated by cycled lighting
Scott A Rivkees1, Linda Mayes, Harris Jacobs
1Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut 06520-8081, USA. Scott.Rivkees@yale.edu
Insights
Cycled lighting in neonatal intensive care units helps premature infants develop day-night activity patterns sooner. Continuous dim lighting delays these crucial rest-activity rhythms in preterm infants.
Area of Science:
- Neonatal development
- Circadian biology
- Sleep science
Background:
- Hospitalized premature infants often experience continuous dim lighting.
- The impact of nursery lighting on infant circadian rhythm development is not well understood.
- Establishing regular rest-activity patterns is vital for infant development.
Purpose of the Study:
- To investigate the effects of cycled lighting versus continuous dim lighting on premature infants' activity patterns.
- To determine if cycled lighting promotes earlier development of day-night rest-activity cycles.
- To assess the entrainment of the circadian clock in developing infants by nursery lighting.
Main Methods:
- Randomly assigned premature infants (<32 weeks postmenstrual age) to either continuous dim light or cycled light conditions.
- Monitored infant activity continuously from enrollment until one month post-discharge.
- Assessed weight and head circumference up to six months post-discharge.
Main Results:
- Infants exposed to cycled lighting showed distinct day-night activity differences within one week of discharge.
- Control infants (continuous dim light) did not exhibit clear day-night activity patterns until 21-30 days post-discharge.
- Even at later stages, infants under cycled lighting displayed stronger diurnal activity patterns compared to controls.
Conclusions:
- Low-intensity cycled lighting in nurseries promotes distinct rest-activity patterns in premature infants shortly after discharge.
- Continuous dim lighting delays the development of these essential day-night rhythms.
- Cycled lighting effectively entrains the circadian clock in developing premature infants.
Objectives:
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.
Methods:
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.
Results:
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).
Conclusion:
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.
