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Published on: December 18, 2013
Development of salivary cortisol circadian rhythm in preterm infants
Katrin Ivars1, Nina Nelson1,2, Annette Theodorsson3
1Department of Pediatrics and Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden.
Insights
Preterm infants establish a salivary cortisol circadian rhythm by one month corrected age, influenced by gestational age, not behavior. This rhythm matures over the first year, nearing full-term infant patterns.
Area of Science:
- Endocrinology
- Neonatal Physiology
- Developmental Pediatrics
Background:
- The development of circadian rhythms, including the hypothalamic-pituitary-adrenal (HPA) axis, is crucial for infant health.
- Cortisol, a key stress hormone, exhibits a diurnal rhythm that matures postnatally.
- Understanding this maturation in preterm infants is vital for assessing their physiological development.
Purpose of the Study:
- To determine the age of salivary cortisol circadian rhythm establishment in preterm infants.
- To investigate the influence of gestational age and postnatal age on this development.
- To explore the relationship between salivary cortisol rhythm and behavioral regularity in early life.
Main Methods:
- A prospective, longitudinal study involving 51 preterm and 130 full-term infants.
- Monthly salivary cortisol measurements taken in the morning, noon, and evening.
- Assessment of behavioral regularity using the Baby Behavior Questionnaire from 28-32 weeks gestational age to 12 months corrected age.
Main Results:
- Salivary cortisol circadian rhythm was established by one month corrected age in preterm infants, persisting throughout the first year.
- Rhythm development was dependent on gestational age, not postnatal age, and differed from full-term infants.
- No correlation was found between salivary cortisol rhythm development and behavioral regularity; topical corticosteroid use was associated with delayed rhythm establishment.
Conclusions:
- Preterm infants establish a salivary cortisol circadian rhythm by one month corrected age.
- Gestational age, rather than postnatal age, is the primary determinant of this rhythm's establishment.
- Salivary cortisol circadian rhythm development in preterm infants is independent of behavioral regularity.
Objectives:
To investigate at what age preterm infants develop a salivary cortisol circadian rhythm and identify whether it is dependent on gestational age and/or postnatal age. To evaluate whether salivary cortisol circadian rhythm development is related to behavioral regularity. To elucidate salivary cortisol levels in preterm infants during the first year of life.
Methods:
This prospective, longitudinal study included 51 preterm infants. 130 healthy full-term infants served as controls. Monthly salivary cortisol levels were obtained in the morning (07:30-09:30), at noon (10:00-12:00), and in the evening (19:30-21:30), beginning at gestational age week 28-32 and continuing until twelve months corrected age. Behavioral regularity was studied using the Baby Behavior Questionnaire.
Results:
A salivary cortisol circadian rhythm was established by one month corrected age and persisted throughout the first year. The preterm infants showed a cortisol pattern increasingly more alike the full-term infants as the first year progressed. The preterm infants increase in behavioral regularity with age but no correlation was found between the development of salivary cortisol circadian rhythm and the development of behavior regularity. The time to establish salivary cortisol circadian rhythm differed between preterm and full-term infants according to postnatal age (p = 0.001) and was dependent on gestational age. Monthly salivary cortisol levels for preterm infants from birth until twelve months are presented. Additional findings were that topical corticosteroid medication was associated with higher concentrations of salivary cortisol (p = 0.02) and establishment of salivary cortisol circadian rhythm occurred later in infants treated with topical corticosteroid medication (p = 0.02).
Conclusions:
Salivary cortisol circadian rhythm is established by one month corrected age in preterm infants. Establishment of salivary cortisol circadian rhythm is related to gestational age rather than to postnatal age. Salivary cortisol circadian rhythm development is not related to behavioral regularity.
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