Toddlers' diurnal cortisol levels affected by out-of-home, center-based childcare and at-home, guardian-supervised childcare: comparison between different caregiving contexts

Latent profile analysis of diurnal cortisol patterns at the ages of 2, 3.5, and 5 years: Associations with childcare setting, child individual characteristics, and maternal distress

This study performed latent profile analysis from more than 4000 saliva cortisol samples collected from children at the ages of 2 (T1), 3.5 (T2), and 5 years (T3). Three clearly different cortisol profiles were identified. The largest group at every age point was the Low/Regular latent profile, in which the cortisol slopes followed typical diurnal variation. A smaller proportion of the children belonged to the latent profile with relatively Low/Flat slope, and a minority belonged to the High/Fluctuating latent group, where the overall cortisol values and variations between the slopes were clearly higher than in the other groups. Most of the children who belonged to the High/Fluctuating group were cared for at home, they had higher temperamental surgency and their mothers had more depressive symptoms than in the other latent profile groups. However, only moderate intraindividual stability in diurnal cortisol profiles was observed across the follow-up period. On average, half of the children moved between the groups from T1 to T3. Neither child temperament, social competence, nor sex explained the stability or movement between the groups across age. Variations in cortisol profiles may be caused by the child's age, and diurnal cortisol rhythm becomes more regular along with development. Methodological issues regarding saliva cortisol research in young children are discussed. Also, more longitudinal research is needed to clarify mechanisms between environmental as well as individual factors and possible dysregulation in a child's HPA axis functioning.

[Analysis of the influence of the timing of enrollment in daycares on child development]

This study aimed to analyze the relationship between the age of enrollment into early childhood education (ECE) programs and child development. This is a cross-sectional study using data from the Birth Cohort of the Western Region of São Paulo, Brazil, with a 36-month follow-up of children born at the University Hospital of the University of São Paulo from 2012 to 2014, and their caregivers who participated in the 36-month follow-up conducted from 2015 to 2017. Child development was measured by the Engle Scale of the Regional Project on Child Development Indicators (PRIDI). ECE programs were evaluated in relation to their quality. The social characteristics of the children and their caregivers, as well as the characteristics of the economic and family context, were used as exposure variables. Our sample consisted of 472 children and their parents/caregivers. The enrollment into daycare from 13 and 29 months was the most frequent. When considered alone, a higher age of enrollment was associated with higher development score [β = 0.21, 95%CI: 0.02; 0.40, p = 0.027]. After adjusting for confounding variables in the regression models, it was observed that being enrolled in a private institution, total time of breastfeeding, time spent by the main caregiver working outside home, and inhibitory control were determinants in explaining the infant development at 36 months in the sample. Older age of entry into ECE programs may have a positive effect on infant development at 36 months of age, but these findings must be carefully considered.

The role of daytime napping on salivary cortisol in children aged 0-5 years: a systematic review and meta-analysis

Cortisol levels are implicated in emotional and cognitive development in children. However, it is not clear whether daytime napping influences cortisol levels in early childhood. This systematic review and meta-analysis aimed to synthesize the available evidence regarding the association between daytime napping and salivary cortisol in early childhood. The Medline, Embase, Web of Science, PsycINFO, and Cochrane Collaboration databases were searched for observational and experimental studies reporting data about napping behavior and salivary cortisol in children 0-5 years of age. Salivary cortisol levels were analyzed in three situations: CAR, cortisol awakening response from nap awakening; PRE-POST, before and after a daytime nap; and DIURNAL, from morning awakening to bedtime. Five studies showed a significant CAR after napping (mean difference, MD: 0.11μg/mL; 95% confidence interval, CI: 0.04, 0.18). In the PRE-POST analysis, a small decrease was observed for at-home naps (MD: -0.05 μg/mL; 95% CI: - 0.09, - 0.02) but not for at-childcare naps (MD: 0.04 μg/mL; 95% CI: - 0.01, 0.09). A similar pattern of DIURNAL salivary cortisol decrease was observed when children took a nap (MD: - 0.34 μg/mL; 95% CI: - 0.41, - 0.28) and when they did not sleep during the day (MD: - 0.28 μg/mL; 95% CI: - 0.38, - 0.19).

CONCLUSIONS

Daytime napping plays a minor role in the fluctuation of salivary cortisol levels during the day. The conditions of the home or the childcare environment under which napping occurs might have a greater influence on cortisol levels than daytime napping itself in early childhood. PROSPERO Identifier: CRD42020212249.

WHAT IS KNOWN

• The regulation of sleep involves circadian rhythmicity of cortisol secretion via activation of the HPA axis and a subsequent release of cortisol upon morning awakening followed by a decline throughout the day.

WHAT IS NEW

• The available evidence supports the occurrence of a cortisol awakening response after a daytime nap. • A small decrease in cortisol after napping was observed when the nap occurred at home but not at childcare. • The conditions of the home or childcare environment under which the nap occurs and the activities before and after napping may have a greater influence on cortisol levels than napping itself.

Children's diurnal cortisol output and temperament in two different childcare settings at 2 and 3.5 years of age

Prior research suggests that child temperament may play an important role in early childhood stress regulation. We compared children's diurnal cortisol and the association between cortisol and temperament in two different childcare settings. Cortisol was measured from saliva samples over 2 days in children (N = 84) attending out-of-home childcare and in children (N = 27), who were cared for at home at the age of 3.5 years. There was no difference between the childcare groups in total diurnal cortisol. However, of the individual measurements, afternoon cortisol levels were higher in the out-of-home childcare group during their childcare day when compared with their home day. Child temperament was not associated with total diurnal cortisol. Comparison with our prior measurements showed that the association between temperamental surgency/extroversion and total diurnal cortisol diminished along with the child age from 2 to 3.5 years in both childcare settings. This may indicate that more extroverted children are physiologically more reactive to environmental stimuli when they are younger, but this association does not appear as the children develop. Our results further suggest that the afternoon hours in the out-of-home childcare may be demanding and accelerate the hypothalamus-pituitary-adrenal axis activation in young children independent of their age.

Reading Skills, Social Competence, and Physiological Stress in the First Grade

An awareness of school-related antecedents of children’s physiological stress at the beginning of school helps educators to prevent and mitigate children’s stress, the one of the major obstacles to their well-being and academic progress. We aimed to study the effect of reading skills and social competence on first-grade students’ salivary cortisol levels in natural settings. Based on previous results of the effects of everyday situations on children’s stress according to gender, we expected that both academic and social skills would affect girls’ physiological stress more, compared to boys. Our sample consisted of 277 students (7–8 years old, 50.2% girls). We used the highest salivary cortisol level of three morning samples and a cortisol level from the middle of the school day as physiological stress indicators. Reading skills were assessed by group-administered tests and social competence by teacher ratings. We found that lower reading comprehension skills and lower disruptiveness were related to higher cortisol levels for girls but not for boys. Higher empathy and lower disruptiveness moderated the effect of better reading comprehension on higher psychological stress in the middle of the school day only for girls. By recognizing the antecedents of children’s stress and supporting their academic and social skills, children’s, especially girls’, physiological self-regulation and coping skills in the primary grades will benefit.

A systematic review of the association between sleep health and stress biomarkers in children

Sleep is intimately linked with the stress response system. While the evidence for this connection has been systematically reviewed in the adult literature, to our knowledge no studies have examined this relationship in young children. Recent scientific interest in understanding the effects of adverse environments in early childhood, including an emphasis on understanding the role of sleep, highlights the importance of synthesizing the current evidence on the relationship between sleep and the stress response system in early childhood. The aim of this systematic review is to examine the relationship between sleep health and biomarkers of physiologic stress (neuroendocrine, immune, metabolic, cardiovascular) in healthy children ages 0-12 y. Following PRISMA guidelines, we identified 68 empirical articles and critically reviewed and synthesized the results across studies. The majority of studies included school-age children and reported sleep dimensions of duration or efficiency. Overall, evidence of associations between sleep health and stress biomarkers was strongest for neuroendocrine variables, and limited or inconsistent for studies of immune, cardiovascular, and metabolic outcomes. Gaps in the literature include prospective, longitudinal studies, inclusion of children under the age of 5 y, and studies using objective measures of sleep.

Child Temperament and Total Diurnal Cortisol in Out-of-Home Center-Based Child Care and in At-Home Parental Care

The association between child temperament characteristics and total diurnal saliva cortisol in 84 children (M = 2.3 years, SD = 0.6) attending out‐of‐home, center‐based child care and 79 children (M = 2.0 years, SD = 0.5) attending at‐home parental care was examined. Saliva samples were collected during two consecutive days, that is, Sunday and Monday, with four samples taken per day. While children higher in surgency had higher total diurnal cortisol production, we did not find evidence that temperament moderated the associations between child‐care context and total diurnal cortisol. Negative affectivity and effortful control were not related to cortisol output. Our findings suggest that temperamental surgency may be associated with higher total cortisol production in early childhood across child‐care settings.

Neuroendocrine, epigenetic, and intergenerational effects of general anesthetics

The progress of modern medicine would be impossible without the use of general anesthetics (GAs). Despite advancements in refining anesthesia approaches, the effects of GAs are not fully reversible upon GA withdrawal. Neurocognitive deficiencies attributed to GA exposure may persist in neonates or endure for weeks to years in the elderly. Human studies on the mechanisms of the long-term adverse effects of GAs are needed to improve the safety of general anesthesia but they are hampered not only by ethical limitations specific to human research, but also by a lack of specific biological markers that can be used in human studies to safely and objectively study such effects. The latter can primarily be attributed to an insufficient understanding of the full range of the biological effects induced by GAs and the molecular mechanisms mediating such effects even in rodents, which are far more extensively studied than any other species. Our most recent experimental findings in rodents suggest that GAs may adversely affect many more people than is currently anticipated. Specifically, we have shown that anesthesia with the commonly used GA sevoflurane induces in exposed animals not only neuroendocrine abnormalities (somatic effects), but also epigenetic reprogramming of germ cells (germ cell effects). The latter may pass the neurobehavioral effects of parental sevoflurane exposure to the offspring, who may be affected even at levels of anesthesia that are not harmful to the exposed parents. The large number of patients who require general anesthesia, the even larger number of their future unexposed offspring whose health may be affected, and a growing number of neurodevelopmental disorders of unknown etiology underscore the translational importance of investigating the intergenerational effects of GAs. In this mini review, we discuss emerging experimental findings on neuroendocrine, epigenetic, and intergenerational effects of GAs.