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Getting rhythm: how do babies do it?
Desaline Joseph1, Nelson W Chong2, Morag E Shanks3
1Division of Child Health, Obstetrics and Gynaecology, School of Medicine, University of Nottingham, Nottingham, UK College of Medicine, Biological Sciences and Psychology, University of Leicester, Leicester, UK.
Insights
Biological rhythms emerge sequentially in infants within the first 18 weeks of life. Cortisol secretion and consolidated night-time sleep appear first, followed by temperature regulation and gene expression, indicating developmental adaptation.
Area of Science:
- Chronobiology
- Developmental Biology
- Human Physiology
Background:
- Infant development involves the maturation of biological rhythms.
- Understanding the precise timing of these rhythms is crucial for assessing healthy development.
Purpose of the Study:
- To investigate the emergence of biological rhythms in human infants.
- To measure age-related changes in core body temperature, hormone secretion (cortisol and 6-sulfatoxymelatonin), and gene expression (H3f3b) during early development.
Main Methods:
- An observational longitudinal study was conducted.
- Measurements included overnight core body temperature, actigraphy, urinary cortisol and 6-sulfatoxymelatonin, and circadian gene expression.
- 35 healthy, full-term infants were monitored from 6 to 18 weeks of age.
Main Results:
- The day-night rhythm of cortisol secretion emerged first at 8 weeks.
- Rhythms of 6-sulfatoxymelatonin and consolidated night-time sleep appeared around 9 weeks.
- Core body temperature regulation aligned with sleep onset by 10 weeks, followed by H3f3b gene expression rhythmicity at 11 weeks.
Conclusions:
- A distinct sequential pattern for diurnal biological rhythm emergence exists in infants aged 6-18 weeks.
- Cortisol secretion and established night-time sleep initiate this sequence.
- This emergence reflects maturation and adaptation to the external environment.
Objectives:
To investigate the emergence of biological rhythms in the first months of life in human infants, by measuring age-related changes in core body temperature during night-time sleep, hormones (cortisol and 6-sulfatoxymelatonin) and the expression of a clock-controlled gene H3f3b in oral epithelial cells.
Design:
Observational longitudinal study.
Setting:
We measured overnight core body temperature, actigraphy, day-night urinary cortisol and 6-sulfatoxymelatonin, as well as circadian gene expression, in infants at home from March 2007 to July 2008 in Leicester.
Participants:
We recruited 35 healthy Caucasian infants who were born at term. They were monitored from 6 to 18 weeks of age.
Results:
At 8 weeks of age the day-night rhythm of cortisol secretion was the first to appear followed by 6-sulfatoxymelatonin 1 week later; at the same time that night-time sleep was established. At 10 weeks, the maximum fall in deep body temperature occurred with the onset of night-time sleep, followed at 11 weeks by the rhythmical expression of the H3f3b gene.
Conclusions:
In human infants, there is a clear sequential pattern for the emergence of diurnal biological rhythms between 6 and 18 weeks of postnatal age, led by the secretion of cortisol and linked with the establishment of consolidated night-time sleep. It is likely that this represents part of a maturation and adaption process as infants gain equilibrium with their external environment after birth.
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