Allostatic Load in Childhood, Adolescence, and Young Adulthood: Are Assumptions of Measurement Invariance Warranted?

OVERVIEW: Allostatic load represents the cumulative toll of chronic mobilization of the body's stress response systems, as indexed by biomarkers. Higher levels of stress and disadvantage predict higher levels of allostatic load, which, in turn, predict poorer physical and mental health outcomes. To maximize the efficacy of prevention efforts, screening for stress- and disadvantage-associated health conditions must occur before middle age-that is, during childhood, adolescence, and young adulthood. However, this requires that models of allostatic load display properties of measurement invariance across age groups. Because most research on allostatic load has featured older adults, it is unclear if these requirements can be met. METHODS: To address this question, we fit a series of exploratory and confirmatory analytic models to data on eight biomarkers using a nationally representative sample of N = 4260 children, adolescents, and young adults drawn from the National Health and Nutrition Examination Survey dataset. RESULTS: Exploratory and confirmatory models indicated that, consistent with allostatic load theory, a unidimensional model was a good fit to the data. However, this model did not display properties of measurement invariance; post-hoc analyses suggested that the biomarkers included in the final confirmatory model were most strongly intercorrelated among young adults and most weakly intercorrelated among adolescents. CONCLUSIONS: These results underscore the importance of testing assumptions about measurement invariance in allostatic load before drawing substantive conclusions about stress, disadvantage, and health by directly comparing levels of allostatic load across different stages of development, while underscoring the need to expand investigations of measurement invariance to samples of longitudinal data.

Maternal prenatal lead levels and neonatal brain volumes: Testing moderations by maternal depressive symptoms and family income.

There is considerable evidence that prenatal lead exposure is detrimental to child cognitive and socio-emotional development. Further evidence suggests that the effects of prenatal lead on developmental outcomes may be conditional upon exposure to social stressors, such as maternal depression and low socioeconomic status. However, no studies have examined associations between these co-occurring stressors during pregnancy and neonatal brain volumes. Leveraging a sample of 101 mother-infant dyads followed beginning in mid-pregnancy, we examined the main effects of prenatal urinary lead levels on neonatal lateralized brain volumes (left and right hippocampus, amygdala, cerebellum, frontal lobes) and total gray matter. We additionally tested for moderations between lead and depressive symptoms and between lead and family income relative to the federal poverty level (FPL) on the same neurodevelopmental outcomes. Analyses of main effects indicated that prenatal lead was significantly (ps < 0.05) associated with reduced right and left amygdala volumes (ßs = -0.23- -0.20). The testing and probing of cross-product interaction terms using simple slopes indicated that the negative effect of lead on the left amygdala was conditional upon mothers having low depressive symptoms or high income relative to the FPL. We interpret the results in the context of trajectories of prenatal and postnatal brain development and susceptibility to low levels of prenatal lead in the context of other social stressors.

Vagal Flexibility Moderates the Links between Observed Sensitive Caregiving in Infancy and Externalizing Behavior Problems in Middle Childhood.

This study explored how patterns of physiological stress reactivity underpin individual differences in sensitivity to early rearing experiences and childhood risk for psychopathology. To examine individual differences in parasympathetic functioning, past research has largely relied on static measures of stress reactivity (i.e., residual and change scores) in infancy which may not adequately capture the dynamic nature of regulation across contexts. Using data from a prospective longitudinal study of 206 children (56% African Americans) and their families, this study addressed these gaps by employing the latent basis growth curve model to characterize the dynamic, non-linear patterns of change in infants' respiratory sinus arrhythmia (i.e., vagal flexibility) across the Face-to-Face Still-Face Paradigm. Furthermore, it investigated whether and how infants' vagal flexibility moderates the links between sensitive parenting, observed during a free play task when children were 6 months of age, and parent-report of children's externalizing problems at 7 years of age. Results of the structural equation models revealed that infants' vagal flexibility moderates the predictive relations between sensitive parenting in infancy and children's later externalizing problems. Simple slope analyses revealed that low vagal flexibility, characterized by less suppression and flatter recovery patterns, exacerbated risk for externalizing psychopathology in the context of insensitive parenting. Children with low vagal flexibility also benefited most from sensitive parenting, as indicated by the lower number of externalizing problems. Findings are interpreted in the light of the biological sensitivity to context model and provide evidence for vagal flexibility as a biomarker of individual's sensitivity to early rearing contexts.

Testing a cascade model linking prenatal inflammation to child executive function.

Inflammation during pregnancy is beginning to be understood as a risk factor predicting poor infant health and neurodevelopmental outcomes. The long-term sequelae associated with exposure to prenatal inflammation are less well established. The current study examined associations between maternal inflammation during pregnancy, markers of infant neurodevelopment (general cognitive ability, negative affect, and sleep quality), and preschool executive function (EF) in a longitudinal sample of 40 African American mother-infant dyads. Mothers completed a blood draw in the third trimester of pregnancy to measure plasma levels of C-reactive protein (CRP) and pro-inflammatory cytokines (e.g., interleukin 6 [IL-6], tumor necrosis factor-alpha [TNF-α]). When infants were 6 months of age, we assessed general cognitive ability via the Bayley-III, negative affect via the Still-Face Paradigm, and sleep quality via actigraphy monitoring. When children were 4 years of age, we assessed their EF ability using four tasks from the EF Touch battery. Elevated levels of maternal CRP, IL-6, and TNF-α were associated with poorer infant general cognitive ability. Although there were no direct effects of prenatal inflammation on preschool EF, we observed an indirect relationship between IL-6 and preschool EF ability via infant general cognitive ability. Our findings suggest that prenatal inflammation may have long-lasting, cascading implications for child neurodevelopment. Implications of these findings for health disparities in women and children of color are discussed.

The Brain and Early Experience Study: Protocol for a Prospective Observational Study.

BACKGROUND: Children raised in conditions of poverty (or near poverty) are at risk for nonoptimal mental health, educational, and occupational outcomes, many of which may be precipitated by individual differences in executive function (EF) skills that first emerge in early childhood. OBJECTIVE: The Brain and Early Experience study considers prenatal and postnatal experiences that may mediate the association between poverty and EF skills, including neural substrates. This paper described the study rationale and aims; research design issues, including sample size determination, the recruitment strategy, and participant characteristics; and a summary of developmental assessment points, procedures, and measures used to test the study hypotheses. METHODS: This is a prospective longitudinal study examining multiple pathways by which poverty influences normative variations in EF skills in early childhood. It is funded by the National Institute of Child Health and Human Development and approved by the institutional review board. RESULTS: Recruitment is complete with a sample of 203 participants, and data collection is expected to continue from September 2018 to February 2024. Of those recruited as low socioeconomic status (SES), 71% (55/78) reported income-to-needs (ITN) ratios of <2.0, and 35% (27/78) reported ITN ratios of <1.0. Among participants recruited into the not-low SES stratum, only 8.8% (11/125) reported ITN ratios of <2.0, and no participant reported ITN ratios of <1.0. The average ITN ratio for participants recruited into the low-income stratum was significantly lower than the average for the high-income recruitment cell (P<.001). Comparable recruitment outcomes were observed for both Black and non-Black families. Overall, the sample has adequate diversity for testing proposed hypotheses, with 13.3% (27/203) of participants reporting ITN ratios of <1 and >32.5% (66/203) reporting ratios of <2.0. CONCLUSIONS: Preliminary results indicate that the recruitment strategy for maximizing variation in family SES was successful, including variation within race. The findings of this study will help elucidate the complex interplay between prenatal and postnatal risk factors affecting critical neurocognitive developmental outcomes in early childhood. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/34854.

Developmental trajectories of toddler sleep problems: can a person-centered approach help identify children at risk?

STUDY OBJECTIVES: Previous research examining toddler sleep problems has relied almost exclusively on variable-centered statistical approaches to analyze these data, which provide helpful information about the development of the average child. The current study examined whether person-centered trajectory analysis, a statistical technique that can identify subgroups of children who differ in their initial level and/or trajectory of sleep problems, has the potential to inform our understanding of toddler sleep problems and their development. METHODS: Families (N = 185) were assessed at 12, 24, 30, and 36 months of child age. Latent class growth analysis was used to test for subgroups that differed in their 24-36 month sleep problems. Subgroups were compared on child 36-month externalizing, internalizing, and total problem behaviors, and on 12 month maternal mental health, inter-parental conflict, and maternal parenting behaviors. RESULTS: Results support a four-class solution, with "low, stable," "low, increasing," "high, increasing," and "high decreasing" classes. The classes whose sleep problems persisted or worsened over time had worse behavioral problems than those whose symptoms improved or remained stably low. Additionally, 12 month maternal depression and global symptom severity, intimate partner violence, and maternal harsh-intrusive parenting behaviors discriminated between the classes that had similar levels of 24 month sleep disturbance but who had diverging trajectories over time. CONCLUSIONS: This statistical approach appears to have the potential to increase understanding of sleep problem trajectories in the early years of life. Maternal mental health, intimate partner violence, and parenting behaviors may be clinically useful markers of risk for the persistence or development of toddler sleep problems.

Context is key: Parasympathetic regulation in the classroom differentially predicts preschoolers' socially competent behaviors.

Research shows that children's early social competence predicts their later academic and interpersonal success. Accordingly, early childhood education programs increasingly aim to evaluate and support children's social skill development. Despite ample theoretical and empirical work demonstrating the role of the parasympathetic nervous system (PNS) in supporting neurophysiological processes that underlie social behaviors, no study has explicitly tested whether the assessment of PNS activity in childhood educational settings provides insight into children's social functioning. The current study addresses this gap by examining the influence of context-specific PNS regulation, assessed via respiratory sinus arrhythmia (RSA), in predicting preschool children's socially competent behavior toward peers in the classroom. Results showed that: (1) RSA withdrawal (e.g., decreases relative to a baseline task) during unstructured classroom activities predicted children's socially competent behaviors during these unstructured activities but not during structured activities, whereas (2) withdrawal during structured classroom activities predicted children's socially competent behaviors during structured activities. These results indicate that PNS activity makes context-specific contributions to children's social behaviors and highlight the importance of assessing neurophysiological regulation in context.

Parenting and maternal reported child sleep problems in infancy predict school-age aggression and inattention.

OBJECTIVE: To examine caregiving predictors of maternal reported sleep problems and child behavioral and cognitive outcomes in early childhood. DESIGN: A prospective longitudinal study from 6 to 84 months of age. SETTING: Lab visits, assessments, and questionnaires conducted with a community-based sample. PARTICIPANTS: One hundred sixty-four African American and White children, their mothers, and teachers. MEASUREMENT: Parenting behavior was measured during a free-play task at 6 months of age, maternal-report of child sleep problems was completed at 6 timepoints, and teacher report of child aggression and attention was collected in kindergarten and second grade. RESULTS: Latent growth curve modeling revealed that maternal reported sleep problems decreased in children from 18 to 84 months and harsh-intrusive parenting at 6 months predicted sleep problems at 18 months. Maternal reported sleep problems at 18 months predicted aggressive behaviors in kindergarten and second grade. CONCLUSION: Parenting at 6 months of age exerts an influence on sleep quality at 18 months which is associated with aggressive behavior in early childhood.

Parasympathetic response to challenge in infancy moderates the effects of sociodemographic risk on academic achievement at school entry.

Exposure to higher levels of sociodemographic risk is associated with lower levels of academic achievement among young children. However, there is variability in the strength of this association, which may be traced to individual differences in physiological processes underlying self-regulation. In the current study, we examined whether the response of the parasympathetic nervous system to challenge, indexed by change in respiratory sinus arrhythmia (RSA), moderated the association between risk and school readiness at 5 years of age in a diverse sample of young children. We found that parasympathetic response to the Still-Face Paradigm moderated the effects of risk on a measure of school readiness, such that there was no association between risk and school readiness among children who exhibited RSA decreases during challenge at 6 months of age, a purported index of self-regulation at this age. For those infants who did not exhibit RSA withdrawal during this challenge, exposure to early cumulative risk was associated with lower scores on achievement assessment. These results speak to the possibility that certain patterns of parasympathetic response can serve as a protective factor for young children growing up in disadvantaged environments.

Infant gut microbiome composition is associated with non-social fear behavior in a pilot study.

Experimental manipulation of gut microbes in animal models alters fear behavior and relevant neurocircuitry. In humans, the first year of life is a key period for brain development, the emergence of fearfulness, and the establishment of the gut microbiome. Variation in the infant gut microbiome has previously been linked to cognitive development, but its relationship with fear behavior and neurocircuitry is unknown. In this pilot study of 34 infants, we find that 1-year gut microbiome composition (Weighted Unifrac; lower abundance of Bacteroides, increased abundance of Veillonella, Dialister, and Clostridiales) is significantly associated with increased fear behavior during a non-social fear paradigm. Infants with increased richness and reduced evenness of the 1-month microbiome also display increased non-social fear. This study indicates associations of the human infant gut microbiome with fear behavior and possible relationships with fear-related brain structures on the basis of a small cohort. As such, it represents an important step in understanding the role of the gut microbiome in the development of human fear behaviors, but requires further validation with a larger number of participants.

Examining Maternal Elaborative Reminiscing as a Protective Factor in the Intergenerational Transmission of Psychopathology.

Most research examining the impact of early parental depression on the developing child has focused on the nature of parenting practices observed in depressed adults. Maternal elaborative reminiscing, or the extent to which mothers elaboratively discuss past shared experiences with their children, has a considerable influence on children's emotional and social development and is understudied within the context of maternal depression. The current study is the first to examine whether maternal elaborative reminiscing in middle childhood mediates the association between exposure to maternal depressive symptoms in infancy and later internalizing and externalizing problems. The study included 206 mother-child dyads recruited from the community who participated in a prospective longitudinal study. Maternal depressive symptoms were assessed when offspring were 6-months old. At 5-years old, dyads were observed during a free play task to measure sensitive and harsh-intrusive parenting and during a reminiscing task to measure maternal elaboration. Teacher-reported internalizing and externalizing problems were collected at age 7. A saturated path model revealed that maternal elaborative reminiscing, but not sensitive or harsh-intrusive parenting, fully mediated the association between maternal depression in infancy and externalizing, but not internalizing, problems. Reduced maternal elaboration during parent-child reminiscing constitutes one way in which risk from early maternal depression is associated with later externalizing problems.

A preliminary study of gut microbiome variation and HPA axis reactivity in healthy infants.

The Hypothalamic Pituitary Adrenal (HPA) axis regulates hormonal responses to stress in both humans and animals and is dysregulated in a wide range of psychiatric disorders. There is strong evidence from rodent studies that gut microbial composition influences HPA axis development. In humans, variation in the gut microbiome has been associated with several psychological domains including depression and cognitive development, but studies focused on HPA axis development are still lacking. We tested whether differences in microbial composition are associated with HPA axis reactivity in a pilot study of 34 healthy human infants. HPA axis reactivity was assessed by measuring salivary cortisol in samples taken both before and after a heel stick, and 16S rRNA amplicon sequencing was used for identification and relative quantification of bacterial taxa. Subjects' alpha diversity levels showed a moderate positive association with their cortisol reactivity at one month of age. Exploratory genus-level analyses suggest that Staphylococcus, Prevotella, and genera in the order Lachnospiraceae may be related to cortisol reactivity at one month as well. The current study gives support for the endocrine pathway as a potential mediator in the microbiome-gut-brain axis during infancy, and as such provides motivation for future clinical work to support the development of stress-response systems through the manipulation of gut microbes.

Observed Peer Competence Moderates Links between Children's Self-Regulation Skills and Academic Performance.

The current study focuses on the relations between observed measures of children's self-regulation and academic achievement, as well as the extent to which observations of children's peer competence in preschool moderates these links. Data were drawn from 102 students (male = 48; M age = 4.82 years, SD age = 0.46 years) enrolled in pre-kindergarten classrooms. A series of linear path models was used to test study hypotheses, and the nature of significant interactions was elucidated by examining simple slopes and regions of significance. Children's self-regulation, but not peer competence, significantly predicted both reading and math performance assessed using the Woodcock Johnson III, ß = .43, p < .001 and ß = .39, p < .001, respectively. Tests of moderation effects revealed that the association between children's poor self-regulation and poor math performance, but not reading performance, ß = -.28, p = .022 and ß = -.11, p = .23, was negated for children with average to high peer competence. These results demonstrate the protective quality of peer competence for academic performance using observational methods collected in preschools.

Longitudinal links between maternal factors and infant cognition: Moderation by infant sleep.

The current study examined the moderating role of infant sleep in the link between maternal factors (i.e., maternal education, depressive symptoms, sleep disturbance) and infant cognition. Data come from 95 African American parent-child dyads. At 3 months of age, infant sleep was objectively measured using videosomnography and actigraphy, from which measures of sleep regulation and consolidation were calculated. Mothers also self-reported their level of education, depressive symptoms, and sleep quality. At 6 months of age, infants completed cognitive assessments, including a measure of general cognitive ability and observed attention behavior. Findings revealed that infant sleep quality interacted with maternal education and sleep disturbances to predict cognition. Specifically, the link between maternal education and infants' attention behavior was significant and positive for infants with better regulated sleep, but not for infants with poorly regulated sleep. Similarly, the link between maternal sleep disturbance and infant cognition depended on infant sleep quality. For infants with poorer sleep consolidation, increased maternal sleep disturbance predicted poorer infant general cognitive ability. For infants with better sleep consolidation, maternal sleep disturbance was positively related to both general cognitive ability and attention behavior. These findings suggest that infant sleep quality moderates the impact of environmental factors on cognitive functioning.

Feeding During Infancy: Interpersonal Behavior, Physiology, and Obesity Risk.

Infancy is a sensitive developmental period that presents both opportunities and challenges for caregivers to feed their infants in ways that support healthy growth and development. The capacity to eat in a way that supports energy (caloric) intake aligned with the body's physiologic need for growth and development appear to diminish in the years following infancy, but the reasons for this and whether this is developmentally typical are unclear. Feeding interactions that undermine infants' ability to regulate their intake in response to hunger and satiety are thought to confer risk for obesity in infancy and beyond. In this integrative review, we consider what we know about the emergence of self-regulation of behavior and emotion from both a behavioral and a physiological perspective. Then, we apply this information to our emerging understanding of how self-regulation of energy intake may be derailed through feeding interactions between caregivers and infants.

Neighborhood deprivation predicts infant sleep quality.

OBJECTIVES: The current study examined the relationship between neighborhood deprivation and infant sleep at 3 months of age. METHODS: Neighborhood and sleep data were collected from 80 African American infants and their caregivers. A composite neighborhood deprivation score was created using census data. Infant sleep was measured via 7 nights of actigraphy monitoring when infants were 3 months of age. Current analyses considered the average number of infant night wakings as an index of sleep quality. Multilevel models were used, in which children (level 1) were nested within census tracts (level 2). RESULTS: Controlling for level 1 covariates, greater neighborhood deprivation (b = 0.07, P < .01), was associated with poorer infant sleep, as characterized by a greater number of wakings during the nighttime sleep period. CONCLUSIONS: Findings suggest that infants who reside in communities marked by higher deprivation experience poorer quality sleep, even after controlling for family-level factors.

Assessment of infant sleep: how well do multiple methods compare?

The current study compares sleep variables obtained from videosomnography, actigraphy, and sleep diaries, three of the most common sleep assessment methods used in infant sleep studies. Using a sample of 90 African American 3-month olds, we compare correlations and discrepancies for seven sleep variables across each of the three pairs of assessment methods for one night of a week-long sleep study. These seven variables are indicative of sleep schedule (e.g. sleep onset time, rise time), duration (e.g. sleep period, sleep time, wake time), and fragmentation (e.g. night wakings, longest sleep period). We find that across all sleep assessment methods, correlations are highest for variables indicative of sleep schedule, and lowest for variables indicative of sleep fragmentation. Comparing the magnitude and significance of the discrepancies, we find that actigraphy and sleep diaries significantly overestimate sleep period duration and underestimate the number of night waking episodes, compared with videosomnography. Actigraphy and sleep diaries were more concordant with one another than with videosomnography. Epoch-by-epoch analyses indicated that actigraphy had low sensitivity to detect wakefulness, compared with videosomnography. Contrary to our hypothesis, the discrepancies between sleep assessment methods did not vary widely based on infant sleep location (own room vs. parent's room) or sleep surface (own bed vs. parent's bed). Limitations and implications of these findings for future research are discussed.

Sociodemographic risk, parenting, and inhibitory control in early childhood: the role of respiratory sinus arrhythmia.

BACKGROUND: Deficits of inhibitory control in early childhood are linked to externalizing behaviors and attention problems. While environmental factors and physiological processes are associated with its etiology, few studies have examined how these factors jointly predict inhibitory control. This study examined whether respiratory sinus arrhythmia (RSA) functioned as a mediator or moderator of both cumulative sociodemographic risk and parenting behaviors on inhibitory control during early childhood. METHODS: The sample included 206 children and their biological mothers. At 24, 30, and 36 months of child age dyads participated in a series of laboratory visits in which sociodemographic, parenting, and baseline RSA (RSAB) data were collected. Inhibitory control was assessed at 36 months using a gift-wrap delay task. RESULTS: A series of structural equation models yielded no evidence that RSAB mediated the relations of risk or parenting and inhibitory control. RSAB moderated the effects of risk, such that high-risk children with low RSAB performed more poorly on tasks of inhibitory control, while high-risk children with high RSAB did not. CONCLUSIONS: These results suggest that higher levels of RSAB may mitigate the influence of environmental risk on the development of inhibitory control early childhood.

Automated respiratory sinus arrhythmia measurement: Demonstration using executive function assessment.

Respiratory sinus arrhythmia (RSA) is a quantitative metric that reflects autonomic nervous system regulation and provides a physiological marker of attentional engagement that supports cognitive and affective regulatory processes. RSA can be added to executive function (EF) assessments with minimal participant burden because of the commercial availability of lightweight, wearable electrocardiogram (ECG) sensors. However, the inclusion of RSA data in large data collection efforts has been hindered by the time-intensive processing of RSA. In this study we evaluated the performance of an automated RSA-scoring method in the context of an EF study in preschool-aged children. The absolute differences in RSA across both scoring methods were small (mean RSA differences = -0.02-0.10), with little to no evidence of bias for the automated relative to the hand-scoring approach. Moreover, the relative rank-ordering of RSA across both scoring methods was strong (rs = .96-.99). Reliable changes in RSA from baseline to the EF task were highly similar across both scoring methods (96%-100% absolute agreement; Kappa = .83-1.0). On the basis of these findings, the automated RSA algorithm appears to be a suitable substitute for hand-scoring in the context of EF assessment.

Children's Executive Function Attenuate the Link Between Maternal Intrusiveness and Internalizing Behaviors at School Entry.

The goal of this study was to examine the independent and interactive roles of harsh-intrusive maternal behaviors and children's executive function in the development of internalizing behaviors across the first years of school. A diverse sample (58% African American, 42% European American) of 137 children (48% female) was followed from kindergarten (age 5 years) through school entry (ages 6-7 years). At age 5, maternal harsh-intrusive parenting behaviors were rated from a mother-child structured play task, and children completed 3 executive function tasks that measured inhibitory control, working memory, and attention set-shifting. Teachers reported on children's internalizing behaviors at ages 5, 6, and 7. Harsh-intrusive parenting behaviors at age 5 years were positively related to internalizing behaviors in the first years of school, whereas high executive function abilities at age 5 years were related to lower internalizing behaviors in the first years of school. In addition, executive function buffered the association between parenting behaviors and internalizing behaviors such that the link between harsh-intrusive parenting and child internalizing behaviors was evident only among children with low executive function and not among children with high executive function. Interventions that focus on reducing negative parenting behaviors and improving children's executive function may prevent internalizing behaviors from increasing during times of social and academic challenge.