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Circadian rhythms in early human development
1Netherlands Institute for Brain Research, Amsterdam, The Netherlands.
Insights
Preterm infants show significant circadian rhythms in body temperature and heart rate, suggesting an internal biological clock. Continuous NICU light may disrupt this natural day-night cycle development.
Area of Science:
- Neonatal physiology
- Circadian biology
- Developmental pediatrics
Background:
- Preterm infants (29-35 weeks) in Neonatal Intensive Care Units (NICUs) experience controlled environments.
- Understanding early biological rhythms is crucial for infant development and health outcomes.
Purpose of the Study:
- To investigate the presence of circadian rhythms in body temperature, heart rate, and rest-activity patterns in preterm infants.
- To explore the influence of a continuously lit NICU environment on the entrainment of biological rhythms.
Main Methods:
- Continuous monitoring of body temperature, heart rate, and rest-activity cycles in 12 preterm infants (29-35 weeks) over 1-2 weeks.
- Recordings were conducted under standardized NICU conditions: constant light, regular intra-gastric feeding, and stable incubator temperature.
Main Results:
- Over 50% of preterm infants exhibited significant circadian rhythms in body temperature and heart rate.
- A notable percentage of infants demonstrated endogenous circadian rhythmicity despite the constant light exposure.
Conclusions:
- Preterm infants possess the capacity for endogenous circadian rhythms early in development.
- Continuous light in NICUs may interfere with the natural development and entrainment of the infant's biological clock to the day-night cycle.
Abstract:
The body temperature, heart rate and rest-activity cycles of 12 low-risk preterm infants (29-35 weeks) were continuously recorded in the neonatal intensive care unit over a period of 1-2 weeks. Throughout the recordings the light was on continuously, the feeding was done intra-gastrically every 2 h and the incubator temperature was constant. Under such conditions a significant circadian rhythm was found in the body temperature and heart rate of more than 50% of the infants. These findings indicate the possible existence of an endogenous circadian rhythm in early human infancy. Since lights are continuously on in the neonatal intensive care unit, this might impair the time of emergence of day-night entrainment of the biological clock in preterm infants.