The Cortisol Awakening Response (CAR) in 2-to 4-year-old Children: Effects of Acute Nighttime Sleep Restriction, Wake Time, and Daytime Napping

The cortisol awakening response (CAR) is presumed critically important for healthy adaptation. The current literature, however, is hampered by systematic measurement difficulties relative to awakening, especially with young children. While reports suggest the CAR is smaller in children than adults, well-controlled research in early childhood is scarce. We examined whether robust CARs exist in 2- to 4-year-old children and if sleep restriction, wake timing, and napping influence the CAR (n?=?7). During a 25-day in-home protocol, researchers collected four salivary cortisol samples (0, 15, 30, 45?min post-wake) following five polysomnographic sleep recordings on nonconsecutive days after 4?hr (morning nap), 7?hr (afternoon nap), 10?hr (evening nap), 13?hr (baseline night), and 16?hr (sleep restriction night) of wakefulness (20 samples/child). The CAR was robust after nighttime sleep, diminished after sleep restriction, and smaller but distinct after morning and afternoon (not evening) naps. Cortisol remained elevated 45?min after morning and afternoon naps. (c) 2011 Wiley Periodicals, Inc. Dev Psychobiol 54:412422, 2012

The CIRCORT database: Reference ranges and seasonal changes in diurnal salivary cortisol derived from a meta-dataset comprised of 15 field studies

Diurnal salivary cortisol profiles are valuable indicators of adrenocortical functioning in epidemiological research and clinical practice. However, normative reference values derived from a large number of participants and across a wide age range are still missing. To fill this gap, data were compiled from 15 independently conducted field studies with a total of 104,623 salivary cortisol samples obtained from 18,698 unselected individuals (mean age: 48.3 years, age range: 0.5–98.5 years, 39% females). Besides providing a descriptive analysis of the complete dataset, we also performed mixed-effects growth curve modeling of diurnal salivary cortisol (i.e., 1–16 h after awakening). Cortisol decreased significantly across the day and was influenced by both, age and sex. Intriguingly, we also found a pronounced impact of sampling season with elevated diurnal cortisol in spring and decreased levels in autumn. However, the majority of variance was accounted for by between-participant and between-study variance components. Based on these analyses, reference ranges (LC/MS–MS calibrated) for cortisol concentrations in saliva were derived for different times across the day, with more specific reference ranges generated for males and females in different age categories. This integrative summary provides important reference values on salivary cortisol to aid basic scientists and clinicians in interpreting deviations from the normal diurnal cycle

The cortisol awakening response (CAR) in toddlers: Nap-dependent effects on the diurnal secretory pattern

INTRODUCTION: Cortisol levels in adults show a sharp decrease from midmorning to midafternoon. Most toddlers take afternoon naps, which is associated with a less mature diurnal pattern characterized by a midday plateau in cortisol secretion. Napping in preschoolers produces a robust cortisol awakening response (CAR), which may account for such maturational differences. This experimental study extends prior work by examining whether the presence and timing of the nap-dependent CAR influences the diurnal cortisol pattern in toddlers. METHODS: Toddlers (n=28; 13 females; 30–36 months) followed a strict biphasic sleep schedule (≥12.5h time in bed; ≥90 min nap) for ≥3 days before each of four randomly ordered, in-home cortisol assessments. For each assessment, saliva samples were obtained at morning awakening, ~09:30, pre-nap, 0, 15, 30, 45, 90, 135 min post-nap awakening (verified with actigraphy), and ~19:30. On one day, children napped at their scheduled time, and parents collected saliva samples. On another day, children missed their nap, and parents collected saliva samples at matched times. On two other days, children napped 4 h (morning) and 7 h (afternoon) after awakening in the morning, during which time researchers collected pre- and post-nap saliva samples. Saliva was assayed for cortisol (μg/dl). RESULTS: Three-level multilevel models were used to estimate the CAR and diurnal cortisol patterns in all four conditions. Compared to the no-nap condition (no observed CAR; b= −0.78, p=0.65), we found a pronounced cortisol rise following the morning nap (b=11.00, p<0.001) and both afternoon naps whether samples were collected by parents (b=5.19, p<0.01) or experimenters (b= 4.97, p<0.01). Napping in the morning resulted in the most robust post-nap cortisol rise (b=10.21, p<0.001). Diurnal patterns were analyzed using piecewise growth modeling that estimated linear coefficients for five separate periods throughout the day (corresponding to morning decline, noon decline, post-nap rise, post-nap decline, and evening decline). We observed a significant post-nap rise in cortisol values on the parent-collected afternoon nap (b=3.41, p<0.01) and the experimenter-collected morning nap (b=7.50, p<0.01) days as compared to the no-nap day (b=−0.17, p=0.82). No other differences in diurnal profiles were observed between the parent-collected nap and no-nap conditions; however, toddlers had a steeper evening decline on the day of the morning nap compared to the parent-collected afternoon nap (b=0.30, p<0.05) and no-nap conditions (b=0.27, p<0.05). DISCUSSION: These well-controlled findings suggest that the presence and timing of daytime naps influence the pattern of diurnal cortisol secretion in toddlers. They also provide support for the hypothesis that napping is the primary state driving the immature midday plateau in cortisol secretion, which becomes more adult-like across childhood. Prior studies of the diurnal cortisol pattern have employed a cubic model, and therefore, have not detected all possible variations due to napping. Our experimental data have important methodological implications for researchers examining associations between the slope of the diurnal cortisol pattern and developmental outcomes, as well as those utilizing afternoon cortisol reactivity protocols in napping children

Sleep Moderates the Association Between Response Inhibition and Self-Regulation in Early Childhood

Early childhood is a time of rapid developmental changes in sleep, cognitive control processes, and the regulation of emotion and behavior. This experimental study examined sleep-dependent effects on response inhibition and self-regulation, as well as whether acute sleep restriction moderated the association between these processes. Preschool children (N = 19; 45.6 ± 2.2 months; 11 female) followed a strict sleep schedule for at least 3 days before each of 2 morning behavior assessments: baseline (habitual nap/night sleep) and sleep restriction (missed nap/delayed bedtime). Response inhibition was evaluated via a go/no-go task. Twelve self-regulation strategies were coded from videotapes of children while attempting an unsolvable puzzle. We then created composite variables representing adaptive and maladaptive self-regulation strategies. Although we found no sleep-dependent effects on response inhibition or self-regulation measures, linear mixed-effects regression showed that acute sleep restriction moderated the relationship between these processes. At baseline, children with better response inhibition were more likely to use adaptive self-regulation strategies (e.g., self-talk, alternate strategies), and those with poorer response inhibition showed increased use of maladaptive self-regulation strategies (e.g., perseveration, fidgeting); however, response inhibition was not related to self-regulation strategies following sleep restriction. Our results showing a sleep-dependent effect on the associations between response inhibition and self-regulation strategies indicate that adequate sleep facilitates synergy between processes supporting optimal social-emotional functioning in early childhood. Although replication studies are needed, findings suggest that sleep may alter connections between maturing emotional and cognitive systems, which have important implications for understanding risk for or resilience to developmental psychopathology

Corrigendum to "The CIRCORT database: Reference ranges and seasonal changes in diurnal salivary cortisol derived from a meta-dataset comprised of 15 field studies" [PNEC 73C (2016) 16-23]

In the published article we unintentionally missed to provide references to study #4 (see Table 1). The source data of study #4 were kindly provided by the TRAILS consortium (Rosmalen et al., 2005)