Neonates born with higher levels of cortisol in their hair take longer time to sleep at 7 months of age, suggests a study presented at the recently concluded annual meeting of the Associated Professional Sleep Societies, SLEEP 2023 and also published in the journal Sleep.^1,2

Researchers from University of Colorado, University of Denver and University of Illinois obtained hair cortisol from 70 infants within 2 days of birth, more than half of whom were female (57.1%). The average gestational age at birth was 39.4 weeks. These infants were a part of the Care Project, a longitudinal study in Denver, Colorado. None of them had received exogenous glucocorticoids prenatally. Sleep was evaluated with the aid of the Brief Infant Sleep Questionnaire (BISQ), filled by the parents, when the infants were 7 months old. The aim of the study was to investigate if neonatal hair cortisol was associated with sleep health in infancy. Neonatal hair cortisol is an index of cortisol production by the fetus.

After adjusting for gestational age at birth and family income-to-needs ratio, the researchers found that higher neonatal hair cortisol levels were indicative of poor sleep at 7 months in the form of longer sleep onset latency as assessed by the BISQ. However, no association was noted between neonatal hair cortisol levels and nighttime sleep duration, number of night awakenings and nighttime wake duration.

This study demonstrates that higher fetal cortisol levels during late pregnancy may adversely affect sleep in infants suggesting a prenatal influence on sleep during infancy. Cortisol is the stress hormone. It is produced by the activity of the hypothalamic-pituitary-adrenal (HPA) axis. The sleep cycle may be disrupted if the HPA axis is active resulting in high levels of cortisol. This manifests as fragmented sleep, insomnia and overall shorter sleep time. The authors write that “specifically, cortisol may inform the shift from multiphasic to monophasic sleep as well as the accumulation of sleep pressure throughout the day, impacting sleep onset latency.” However, only sleep onset latency was affected and not overall sleep. Nevertheless, these findings merit further studies to investigate the impact of high neonatal cortisol on sleep during childhood.

 References

1. Benefield T, et al. Abstract 0121. Newborn hair cortisol and sleep health in infancy. Sleep. 2023 May;46(Suppl 1):A54–A55. https://doi.org/10.1093/sleep/zsad077.0121
2. https://www.sleepmeeting.org/newborns-higher-hair-cortisol-levels-take-longer-fall-asleep/, May 30, 2023. Accessed on June 12, 2023.