Longitudinal associations between infections and atopic disorders across childhood and dysregulated adrenocortical functioning in early adolescence

Cesarean delivery and infant cortisol regulation

BACKGROUND

Cesarean delivery reduces the risk of infant and maternal morbidity and mortality when medically indicated, however, the cesarean delivery rate is estimated to be two to three times higher than medically necessary. The World Health Organization and American College of Obstetricians and Gynecologists have expressed concern over the high rates of cesarean delivery, citing evidence that cesarean delivery has negative short- and long-term consequences for the health of the infant, mother, and for future pregnancies. Infants delivered by cesarean are at an increased risk of metabolic disease and immune dysfunction throughout the lifespan. Preliminary research suggests that the hypothalamic pituitary adrenal (HPA) axis is a plausible pathway linking cesarean delivery to poor health later in life. The present study examines the relation between mode of delivery and HPA axis function in six-month-old infants. We also examine whether the cesarean delivery was elective or indicated altered to the relation between mode of delivery and infant cortisol profiles.

METHODS

The sample included 136 mother/infant pairs. Thirty-nine women delivered by cesarean and 97 delivered vaginally. Maternal and infant medical records were reviewed for prenatal medical history and birth outcomes. Infant saliva was collected for cortisol analysis at a 6-month well-baby checkup. Samples were collected upon arrival to the appointment (baseline) and 20 min after exposure to a painful stressor, the inoculation procedure (response). A mixed model ANCOVA was conducted to determine whether salivary cortisol concentrations differed between the two delivery groups. To examine whether complications related to having an indicated cesarean delivery contributed to any association between mode of delivery and cortisol production, cortisol concentrations were compared between the subgroup of infants whose cesarean deliveries were elective (e.g. maternal request or previous cesarean delivery) to infants delivered vaginally.

RESULTS

Infants delivered by cesarean had lower cortisol concentrations at baseline and after the inoculation procedure compared to those delivered vaginally. Further, the relation between mode of delivery and cortisol levels persisted even when the analyses were restricted to compare only the elective cesarean deliveries (e.g. maternal request or previous cesarean delivery) to those delivered vaginally.

DISCUSSION

This study provides evidence for an association between cesarean delivery and infant HPA axis function in infancy. Findings are consistent with the hypothesis that the HPA axis is a plausible pathway that links cesarean delivery with long-term health outcomes.

Altered hypothalamus-pituitary-adrenal axis function: A relevant factor in the comorbidity of atopic eczema and attention deficit/hyperactivity disorder?

Epidemiological data show a significant association between childhood atopic eczema (AE) and an increased risk to develop attention deficit/hyperactivity disorder (ADHD). However, the underlying mechanisms of the comorbidity of AE and ADHD are mostly unknown. We investigated whether alterations of hypothalamus-pituitary-adrenal (HPA) axis function represent a shared feature of AE and ADHD potentiating AE-ADHD comorbidity. Children aged 6-12 years with AE, ADHD, or comorbid AE + ADHD and healthy control (HC) children were examined cross-sectionally (N = 145). To evaluate HPA axis function, salivary cortisol in response to psychosocial stress (Trier Social Stress Test for Children, TSST-C), after awakening (cortisol awakening response, CAR), and throughout the day (short diurnal profile) and hair cortisol capturing long-term HPA axis activity were assessed. Quantile regression analyses showed an attenuated cortisol response (% maximum change) to the TSST-C in children with ADHD compared to HC. A diminished cortisol response to acute stress was also observed in the comorbid AE + ADHD group, in which the reduction was numerically even more pronounced. Contrary to our previous findings, no alteration of the cortisol response to the TSST-C was observed in children with AE. However, in children with AE, increased ADHD-like behavior (i.e., inattention, impulsivity, and overall ADHD symptom severity) was associated with a reduced HPA axis response to acute stress. No such associations were observed in children without AE. Groups did not differ in CAR, short diurnal profile, and hair cortisol. These findings underscore the potential relevance of HPA axis function in the pathophysiology of AE and ADHD with emphasis on stress reactivity. Additional studies are required to further explore the separate and joint role of the HPA axis in the pathophysiology of AE and ADHD.

Children's anxiety symptoms and salivary immunoglobulin A: A mutual regulatory system?

Anxiety can impact the immune system resulting in negative health outcomes. Salivary immunoglobulin A (sIgA) is a first line of defense against foreign antigens, with lowered levels indicative of weakened mucosal immunity. Little is known about how anxiety symptoms affect the diurnal rhythm of sIgA secretion, or the longitudinal transactional sequence between the two in children and adolescents. The goals of the two studies were to: (i) explore the concurrent associations between self-reported anxiety symptoms and diurnal variations of sIgA across the day using repeated daily samples of sIgA; and (ii) examine transactional relations between children's anxiety and aggregated total amount of sIgA levels across successive periods from middle childhood (Wave 1; ages 9-12) to early adolescence (Wave 2; ages 12-15), and from early to mid- adolescence (Wave 3; ages 15-18). Concurrent results showed a steeper (positive) rise in diurnal slope of sIgA from awakening to 5 hr post-awakening in children with higher anxiety. Longitudinally, higher levels of total anxiety, and specifically, worries at Wave 1 significantly predicted lower cumulative daily levels of sIgA 3 years later at Wave 2. Lowered sIgA levels at Wave 2 in turn predicted higher anxiety at Wave 3, illustrating a "vicious cycle" feedback loop. These findings broaden our understanding of the developmental links between anxiety symptoms, the immune system, and health.

Diurnal cortisol slopes and mental and physical health outcomes: A systematic review and meta-analysis

Changes in levels of the stress-sensitive hormone cortisol from morning to evening are referred to as diurnal cortisol slopes. Flatter diurnal cortisol slopes have been proposed as a mediator between chronic psychosocial stress and poor mental and physical health outcomes in past theory and research. Surprisingly, neither a systematic nor a meta-analytic review of associations between diurnal cortisol slopes and health has been conducted to date, despite extensive literature on the topic. The current systematic review and meta-analysis examined associations between diurnal cortisol slopes and physical and mental health outcomes. Analyses were based on 179 associations from 80 studies for the time period up to January 31, 2015. Results indicated a significant association between flatter diurnal cortisol slopes and poorer health across all studies (average effect size, r=0.147). Further, flatter diurnal cortisol slopes were associated with poorer health in 10 out of 12 subtypes of emotional and physical health outcomes examined. Among these subtypes, the effect size was largest for immune/inflammation outcomes (r=0.288). Potential moderators of the associations between diurnal cortisol slopes and health outcomes were examined, including type of slope measure and study quality indices. The possible roles of flatter slopes as either a marker or a mechanism for disease etiology are discussed. We argue that flatter diurnal cortisol slopes may both reflect and contribute to stress-related dysregulation of central and peripheral circadian mechanisms, with corresponding downstream effects on multiple aspects of biology, behavior, and health.