Lack of Adult-Type Salivary Cortisol Circadian Rhythm in Hospitalized Preterm Infants

Abstract

Background/Aims: Knowledge of the presence or absence of cortisol (F) circadian rhythm in preterm infants is important for the interpretation of F measurements made in samples taken for both clinical and research purposes. Little is known about its emergence in very preterm infants. This study examines circadian rhythm in F secretion in hospitalized infants born before 30 weeks’ gestation. Methods: Design: Prospective longitudinal observational study. Subjects: 11 infants admitted consecutively and born before 30 completed weeks of gestation. Measurements: F was measured by highly specific radioimmunoassay on morning and evening saliva samples gathered at weekly intervals until discharged home. Circadian rhythm was defined as ≧40% reduction from morning to evening level. Results: For all data, the median salivary F was 10.3 nmol/l (range <0.5–372.8). F levels were highest in the first 3 weeks of life. No infants displayed classical circadian rhythm for 4 weeks or more prior to being discharged from hospital. The other infants showed randomly distributed morning and evening F values with a trend in 4 infants towards periods of consistently higher evening than morning values. Conclusion: Adult-type F circadian rhythm is rarely evident in hospitalized preterm infants born before 30 weeks’ gestation.

Stress : Clinical and Developmental Aspects of Salivary Cortisol in Infants

“…All samples were collected on the same day and not for the purpose of investigating CCR development. Viewing our results in relation to CCR development and comparing them with the diversity of approaches and results from earlier studies entailing a) infants at early age (<three weeks PNA) [69,71,73], b)…”

“…The primary focus was not necessarily on CCR development [64]. The results from studies on preterm infants were either in line with ours regarding time for onset of CCR [70,74], or the studies were not designed to cover that time period (one month CA) [68,69,[71][72][73]. De Weerth et al investigated the dynamics of cortisol levels among infants age nine months, with risk factors similar to our group of infants at high psychosocial risk, and concluded that high maternal stress predicts high infant cortisol levels with high total AUC; our findings of high variability in AUC along with CCR curves that do not flatten over time are consistent with these results.…”

“…Cortisol levels peak in the morning and subsequently drop to a nadir in the evening [59,60] Seven earlier studies have explored the development of CCR in preterm infants [68][69][70][71][72][73][74], three of which investigated cortisol in saliva [69][70][71]. To date, there has been no general consensus regarding when CCR is established.…”

“…Seven earlier studies have investigated development of salivary CCR in full-term infants [61][62][63][64][65][66][67] and an additional seven studies have investigated CCR development in preterm infants [68][69][70][71][72][73][74] (saliva, plasma, or serum), whereas only one study has examined CCR in high psychosocial risk infants at <twelve months of age [100] (saliva).…”

“…Our results, which represent a unique addition to the literature in this age group of infants at high psychosocial risk, show that such young infants are also at risk of long-term elevated cortisol levels and that CCR development, although present, is disturbed. It is well-known that younger infants have higher interindividual variations in absolute morning-evening cortisol indices [65,67,[69][70][71] and they also vary in basal cortisol levels both intraindividually and interindividually [191].…”