Emotion regulation and cortisol response to the still-face procedure in preterm and full-term infants

Assessment of salivary cortisol dynamics in an infantry training exercise: a pilot study

INTRODUCTION

Measuring cortisol during military training offers insights into physiological responses to stress. We attempted precisely timed, cortisol awakening response (CAR) and pre-sleep cortisol (PSC), and diurnal slope (peak morning minus evening cortisol), during a British Army exercise. We aimed to understand cortisol dynamics and evaluate the feasibility of CAR and PSC in this environment.

METHOD

Setting: high-intensity, 10-day infantry exercise. Participants: regular infantry soldiers exercising (EX, n=25) or headquarters-based (HQ, n=6). Participants undertook PSC and WAKE and WAKE+30 min samples after 1-2 days, 5-6 days and 9-10 days. Wrist-worn GENEActiv accelerometers were used to assess sleep duration in EX only. Samples taken ±15 min from prespecified time points were deemed adherent. Validated questionnaires were used to measure resilience and perceived stress. Cortisol and cortisone were measured simultaneously by liquid chromatography tandem mass spectrometry.

RESULTS

From adherent participants' samples, CAR was positive and tended to decrease as the exercise progressed. From all available data, HQ demonstrated greater diurnal slope than EX (F=7.68, p=0.02), reflecting higher morning cortisol (F=4.72, p=0.038) and lower PSC (p=0.04). No differences were seen in cortisol:cortisone ratio. 26.1% of CAR samples were adherent, with moderately strong associations between adherence and stress (r=0.41, p=0.009) but no association between adherence and day of exercise (χ2=0.27, p=0.8), sleep duration (r=-0.112, p=0.43) or resilience (r=-0.79, p=0.75). Test-retest reliability ratings for CAR were Cronbach's α of 0.48, -11.7 and 0.34 for the beginning, middle and end of the exercise, respectively.

CONCLUSIONS

We observed a reduction in morning cortisol and decreased diurnal slope during a high-intensity military exercise, compared with the HQ comparator cohort in whom diurnal slope was preserved. A carefully timed CAR was not feasible in this setting.

Relationships between cortisol levels across early childhood and processing speed at age 4.5 years in children born very preterm

Children born very low gestational age (VLGA, 29-32 weeks gestational age [GA]) display slower processing speed and altered hypothalamic pituitary adrenal (HPA) axis function, with greater effects in those born extremely low gestational age (ELGA; 24-28 weeks GA). We investigated trajectories of HPA axis activity as indexed by cortisol output and patterns across cognitive assessment at ages 1.5, 3 and 4.5 years, comparing children born ELGA and VLGA and associations with 4.5-year processing speed. In a prospective longitudinal cohort study, infants born very preterm (<33 weeks gestation) returned for developmental assessment at ages 1.5, 3, and 4.5 years. At each age, children completed standardized cognitive testing and saliva samples collected before (Pretest), during (During) and after (End) challenging cognitive tasks were assayed for cortisol. For the total group (n = 188), cortisol area under the curve with respect to ground (AUCg) decreased, while cortisol reactivity to challenge (Pre-test to During) increased from 1.5 to 3 years, remaining stable to 4.5 years. This longitudinal pattern was related to higher Processing Speed (WPPSI-IV) scores at 4.5 years. Children born ELGA displayed higher AUCg than VLGA, particularly at age 3, driven by higher Pre-test cortisol levels. Overall, relative to those born VLGA, children born ELGA displayed greater cortisol responsivity to cognitive challenge. A higher setpoint of cortisol levels at age 3-years in children born ELGA may reflect altered HPA axis regulation more broadly and may contribute to difficulties with information processing in this population, critical for academic and social success.

Cortisol levels are related to neonatal pain exposure in children born very preterm at age 18 months in two independent cohorts

Exposure to pain-related stress from frequent invasive procedures in the neonatal intensive care unit (NICU) has been associated with altered physiological stress regulation, neurodevelopment, and behavior in children born very preterm (≤32 weeks gestation). Previously, in a cohort born 2003-2006 (Cohort 1), we found that, at 18 months corrected age (CA), children born extremely low gestational age (ELGA; 24-28 weeks) and very low gestational age (VLGA; 29-32 weeks), had higher pre-test cortisol levels and a different pattern of cortisol output across a developmental assessment involving cognitive challenge compared to children born full-term (FT; 39-41 weeks). Also, greater neonatal pain-related stress exposure among the preterm children was related to higher pre-test cortisol levels. Given the adverse long-term effects of neonatal pain in preterm infants and the ensuing rise in clinical concerns to appropriately manage pain in the NICU in recent years, we aimed to examine whether our findings from Cohort 1 would still be evident in an independent cohort (Cohort 2) born 2006-2011 and recruited from the same tertiary NICU in Vancouver, Canada. We also compared the cortisol patterns, clinical and socio-demographic factors, and their interrelationships between the two cohorts. In Cohort 2, our findings using multi-level modeling support and extend our earlier findings in Cohort 1, demonstrating that children born ELGA display higher pre-test cortisol levels than FT. As well, greater cortisol output across assessment was related to more anxiety/depressive behaviors in children born VLGA. Importantly, children born ELGA were exposed to less neonatal pain/stress, mechanical ventilation, and morphine in Cohort 2 than Cohort 1. In both cohorts, however, cortisol levels and patterns were related to neonatal pain/stress and clinical factors (days on mechanical ventilation, overall morphine exposure). Despite less exposure to pain/stress and adverse clinical factors in Cohort 2 compared to Cohort 1, cortisol levels and patterns across cognitive challenge in preterm children at 18-month CA were consistent across the two independent cohorts. These findings highlight that, despite improvements to neonatal care, children born extremely preterm continue to display altered HPA axis activity, which is associated with their poorer neurodevelopmental and behavioral outcomes.

Association of Preterm Birth and Socioeconomic Status With Neonatal Brain Structure

Importance

Preterm birth and socioeconomic status (SES) are associated with brain structure in childhood, but the relative contributions of each during the neonatal period are unknown.

Objective

To investigate associations of birth gestational age (GA) and SES with neonatal brain morphology by testing 3 hypotheses: GA and SES are associated with brain morphology; associations between SES and brain morphology vary with GA; and associations between SES and brain structure and morphology depend on how SES is operationalized.

Design, Setting, and Participants

This cohort study recruited participants from November 2016 to September 2021 at a single center in the United Kingdom. Participants were 170 extremely and very preterm infants and 91 full-term or near-term infants. Exclusion criteria were major congenital malformation, chromosomal abnormality, congenital infection, cystic periventricular leukomalacia, hemorrhagic parenchymal infarction, and posthemorrhagic ventricular dilatation.

Exposures

Birth GA and SES, operationalized at the neighborhood level (using the Scottish Index of Multiple Deprivation), the family level (using parental education and occupation), and subjectively (World Health Organization Quality of Life measure).

Main Outcomes and Measures

Brain volume (85 parcels) and 5 whole-brain cortical morphology measures (gyrification index, thickness, sulcal depth, curvature, surface area) at term-equivalent age (median [range] age, 40 weeks, 5 days [36 weeks, 2 days to 45 weeks, 6 days] and 42 weeks [38 weeks, 2 days to 46 weeks, 1 day] for preterm and full-term infants, respectively).

Results

Participants were 170 extremely and very preterm infants (95 [55.9%] male; 4 of 166 [2.4%] Asian, 145 of 166 [87.3%] White) and 91 full-term or near-term infants (50 [54.9%] male; 3 of 86 [3.5%] Asian, 78 of 86 [90.7%] White infants) with median (range) birth GAs of 30 weeks, 0 days (22 weeks, 1 day, to 32 weeks, 6 days) and 39 weeks, 4 days (36 weeks, 3 days, to 42 weeks, 1 day), respectively. In fully adjusted models, birth GA was associated with a higher proportion of brain volumes (27 of 85 parcels [31.8%]; β range, -0.20 to 0.24) than neighborhood-level SES (1 of 85 parcels [1.2%]; β = 0.17 [95% CI, -0.16 to 0.50]) or family-level SES (maternal education: 4 of 85 parcels [4.7%]; β range, 0.09 to 0.15; maternal occupation: 1 of 85 parcels [1.2%]; β = 0.06 [95% CI, 0.02 to 0.11] respectively). There were interactions between GA and both family-level and subjective SES measures on regional brain volumes. Birth GA was associated with cortical surface area (β = 0.10 [95% CI, 0.02 to 0.18]) and gyrification index (β = 0.16 [95% CI, 0.07 to 0.25]); no SES measure was associated with cortical measures.

Conclusions and Relevance

In this cohort study of UK infants, birth GA and SES were associated with neonatal brain morphology, but low GA had more widely distributed associations with neonatal brain structure than SES. Further work is warranted to elucidate the mechanisms underlying the association of both GA and SES with early brain development.