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Published on: December 18, 2013
Development of Salivary Cortisol Circadian Rhythm and Reference Intervals in Full-Term Infants
Katrin Ivars1, Nina Nelson2, Annette Theodorsson3
1Department of Clinical and Experimental Medicine, Division of Pediatrics, Faculty of Health Sciences, Linköping University, Linköping, Sweden.
Insights
Infant cortisol circadian rhythm is established by one month of age, earlier than previously thought. This study provides crucial salivary cortisol reference intervals for the first year of life in healthy infants.
Area of Science:
- Endocrinology
- Pediatrics
- Chronobiology
Background:
- Cortisol plasma concentrations exhibit circadian rhythms in adults and children over one year old.
- Previous research has yielded conflicting findings on the establishment age of cortisol circadian rhythm.
- Infant cortisol rhythm development, behavioral regularity, and trauma influences remain understudied.
Purpose of the Study:
- To determine the age of cortisol circadian rhythm establishment in infants.
- To investigate the impact of behavioral regularity and daily life trauma on rhythm establishment.
- To establish age-related salivary cortisol reference intervals for the first year of life.
Main Methods:
- A prospective, longitudinal study involving 130 healthy, full-term infants.
- Monthly saliva sampling over 12 months (morning, noon, evening) on consecutive days.
- Parental questionnaires (Baby Behavior Questionnaire, Life Incidence of Traumatic Events checklist) assessed behavioral regularity and trauma exposure.
Main Results:
- A group-level circadian rhythm of salivary cortisol secretion was evident by one month of age and persisted throughout the first year.
- Significant individual variability in cortisol rhythm was observed.
- No correlation was found between cortisol rhythm development and behavioral regularity or trauma exposure.
Conclusions:
- Cortisol circadian rhythm is established in infants by one month of age, earlier than previously reported.
- This study provides the first age-related reference intervals for salivary cortisol in healthy infants during their first year.
- Behavioral regularity and trauma do not appear to influence the early establishment of infant cortisol rhythm.
Background:
Cortisol concentrations in plasma display a circadian rhythm in adults and children older than one year. Earlier studies report divergent results regarding when cortisol circadian rhythm is established. The present study aims to investigate at what age infants develop a circadian rhythm, as well as the possible influences of behavioral regularity and daily life trauma on when the rhythm is established. Furthermore, we determine age-related reference intervals for cortisol concentrations in saliva during the first year of life.
Methods:
130 healthy full-term infants were included in a prospective, longitudinal study with saliva sampling on two consecutive days, in the morning (07:30-09:30), noon (10:00-12:00) and evening (19:30-21:30), each month from birth until the infant was twelve months old. Information about development of behavioral regularity and potential exposure to trauma was obtained from the parents through the Baby Behavior Questionnaire and the Life Incidence of Traumatic Events checklist.
Results:
A significant group-level circadian rhythm of salivary cortisol secretion was established at one month, and remained throughout the first year of life, although there was considerable individual variability. No correlation was found between development of cortisol circadian rhythm and the results from either the Baby Behavior Questionnaire or the Life Incidence of Traumatic Events checklist. The study presents salivary cortisol reference intervals for infants during the first twelve months of life.
Conclusions:
Cortisol circadian rhythm in infants is already established by one month of age, earlier than previous studies have shown. The current study also provides first year age-related reference intervals for salivary cortisol levels in healthy, full-term infants.
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