Increased risk of attention-deficit/hyperactivity disorder in adolescents with high salivary levels of copper, manganese, and zinc.

Exposure to toxic heavy metals has been associated with the development of attention-deficit/hyperactivity disorder (ADHD). However, fewer studies have examined the associations between abnormal levels of essential trace metals and ADHD, and none have done so using saliva. We investigated whether salivary metals were associated with ADHD in adolescents aged 12 from the Family Life Project (FLP) using a nested case-control study design that included 110 adolescents who met diagnostic criteria for inattentive (ADHD-I), hyperactive-impulsive (ADHD-H), or combined type ADHD (ADHD-C) (cases) and 173 children who did not (controls). We used inductively coupled plasma optical emission spectrophotometry to measure chromium, copper, manganese, and zinc in saliva samples. We employed logistic regression models to examine associations between quartile levels of individual metals and ADHD outcomes by subtype. Salivary copper levels were significantly associated with increased odds of any ADHD diagnosis (OR = 3.31, 95% CI: 1.08-10.12; p = 0.04) and with increased odds of ADHD-C diagnosis (OR = 8.44, 95% CI: 1.58-45.12; p = 0.01). Salivary zinc levels were significantly associated with increased odds of ADHD-C diagnosis (OR = 4.06, 95% CI: 1.21-13.69; p = 0.02). Salivary manganese levels were also significantly associated with increased odds of ADHD-C diagnosis (OR = 5.43, 95% CI: 1.08-27.27, p = 0.04). This is the first study using saliva to assess metal exposure and provide a potential link between salivary levels of copper, manganese, and zinc and ADHD diagnoses in adolescents. Public health interventions focused on metal exposures might reduce ADHD incidence in low-income, minority communities.

Environmental tobacco smoke exposure is associated with increased levels of metals in children's saliva.

BACKGROUND: Exposure to environmental tobacco smoke (ETS) has been associated with detectable levels of cotinine (a nicotine metabolite) in children's saliva. However, tobacco smoke also contains toxic and essential trace metals, including chromium (Cr), copper (Cu), lead (Pb), manganese (Mn), nickel (Ni) and zinc (Zn). OBJECTIVE: The current study examines whether there is a relationship between ETS exposure, as gauged by salivary cotinine, and salivary levels of these metals in a subset (n = 238) of children from the Family Life Project. METHODS: Using inductively-coupled-plasma optical emission spectrophotometry, we measured levels of metals in saliva from children at ~90 months of age. Salivary cotinine was measured using a commercial immunoassay. RESULTS: We found that Cr, Cu, Mn, and Zn were detected in most samples (85-99%) with lower levels of detection for Pb and Ni (9.3% and 13.9% respectively). There were no significant differences in any of the metal concentrations between males and females, nor were levels associated with body mass index, although significant differences in salivary Cr and Mn by race, state and income-to-needs ratio were observed. Children with cotinine levels >1 ng/ml had higher levels of Zn (b = 0.401, 95% CI: 0.183 to 0.619; p = 0.0003) and Cu (b = 0.655, 95% CI: 0.206 to 1.104; p = 0.004) compared to children with levels <1 ng/ml, after controlling for multiple confounders, including sex, race, BMI and income-to-needs ratio. Further, we show that children whose cotinine levels were >1 µg/L were more likely to have detectable levels of Pb in their saliva (b = 1.40, 95% CI: 0.424 to 2.459; p = 0.006) compared to children with cotinine levels <1 ng/ml, also considering confounders. IMPACT STATEMENT: This is the first study to demonstrate significant associations between salivary cotinine and salivary levels of Cu, Zn and Pb, suggesting that environmental tobacco smoke exposure my be one source of increased children's exposure to heavy metals. This study also demonstrates that saliva samples can be used to measure heavy metal exposure, and thus serve as a non-invasive tool for assessing a broader range of risk indicators.

Capturing Environmental Dimensions of Adversity and Resources in the Context of Poverty Across Infancy Through Early Adolescence: A Moderated Nonlinear Factor Model.

Income, education, and cumulative-risk indices likely obscure meaningful heterogeneity in the mechanisms through which poverty impacts child outcomes. This study draws from contemporary theory to specify multiple dimensions of poverty-related adversity and resources, with the aim of better capturing these nuances. Using data from the Family Life Project (N = 1,292), we leveraged moderated nonlinear factor analysis (Bauer, 2017) to establish group- and longitudinally invariant environmental measures from infancy to early adolescence. Results indicated three latent factors-material deprivation, psychosocial threat, and sociocognitive resources-were distinct from each other and from family income. Each was largely invariant across site, racial group, and development and showed convergent and discriminant relations with age-twelve criterion measures. Implications for ensuring socioculturally valid measurements of poverty are discussed.

Executive Function and BMI Trajectories Among Rural, Poor Youth at High Risk for Obesity.

OBJECTIVE: The aim of this study was to identify longitudinal trajectories of conjoint development of executive function (EF) and obesity among a diverse sample of poor, rural youth and to evaluate individual differences in infant growth, parental BMI, and cumulative risk. METHODS: Participants included 948 youth from the Family Life Project. Child anthropometrics were measured at 2 and 6 months and at 2, 3, 4, 5, 7, and 12 years. EF tasks were administered at 3, 4, and 5 years. Mothers reported youth birth weight, parental height and weight, and cumulative risk indicators. RESULTS: Multidimensional growth mixture modeling identified three classes: "High EF - High Obesity Resilience"; "Low EF - Delayed-Onset Severe Obesity"; and "Low EF - Early-Onset Severe Obesity." Youth in the low-EF, early-onset class displayed higher birth weight and BMI at 6 months, whereas the low-EF, delayed-onset class had rapid weight gain during infancy, parents with class II obesity, and greater cumulative risk and was more likely to be Black and female. CONCLUSIONS: Despite increased obesity risk among this sample, the majority of youth exhibited higher EF and some degree of obesity resilience. Youth with EF deficits displayed the greatest risk for severe obesity but had differing BMI trajectories and obesity risk profiles, which has implications for obesity intervention.

Measurement models for studying child executive functioning: Questioning the status quo.

Despite widespread interest in the construct of executive functioning (EF), we currently lack definitive evidence regarding the best measurement model for representing the construct in substantive analyses. The most common practice is to represent EF ability as a reflective latent variable, with child performance on individual EF tasks as observed indicators. The current article critically evaluates the dominant use of reflective latent variable models in the child EF literature and compares them to composite models, a reasonable alternative. We review the literature suggesting that reflective latent variable models may not be the most appropriate representation of the construct of EF. Using preschool (Mage = 48.3 months) and first grade (Mage = 83.5 months) data from the Family Life Project (N = 920), we also investigate the implications of measurement model specification for the interpretation of study findings. Children in this sample varied in terms of sex (49% male), race (43% black) and socioeconomic status (76% low-income). Our findings show that the conclusions we draw from 2 substantive analyses differ depending on whether EF is modeled as a reflective latent variable versus a composite variable. We describe the implications of these findings for research on child EF and offer practical recommendations for producers and consumers of developmental research. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Leveraging item accuracy and reaction time to improve measurement of child executive function ability.

Traditionally, executive function (EF) tasks have been scored using either accuracy or reaction time (RT) metrics. The current study, which includes 1,015 first-grade children from the Family Life Project, demonstrates a new scoring approach for the Hearts and Flowers (HF) task that uses both item-level accuracy and RT data to estimate latent EF ability. Our primary aim was to compare scores derived from this approach to standard scores often reported in the HF literature. A second aim was to test whether item-level accuracy and RT data were differentially related to latent EF ability, depending on children's overall level of task performance. Our results indicated that item-level accuracy and RT data both convey unique information related to latent EF ability but that the relative contributions of each source of data vary across children. Accuracy was comparatively more informative of latent ability in children with lower HF task performance, while RT was comparatively more informative of latent ability in children with higher overall performance. Moreover, item-level RT was differentially related to latent EF ability for children in lower versus higher performing groups. Whereas faster responding was associated with higher ability in the higher performing group, slower responding was associated with higher ability for the lower performing group. Latent EF ability was related to criterion measures in ways comparable to traditional scores. Results are discussed in relation to the broader EF assessment literature. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Early life predictors of attention deficit/hyperactivity disorder symptomatology profiles from early through middle childhood.

This study used repeated measures data to identify developmental profiles of elevated risk for ADHD (i.e., six or more inattentive and/or hyperactive-impulsive symptoms), with an interest in the age at which ADHD risk first emerged. Risk factors that were measured across the first 3 years of life were used to predict profile membership. Participants included 1,173 children who were drawn from the Family Life Project, an ongoing longitudinal study of children's development in low-income, nonmetropolitan communities. Four heuristic profiles of ADHD risk were identified. Approximately two thirds of children never exhibited elevated risk for ADHD. The remaining children were characterized by early childhood onset and persistent risk (5%), early childhood limited risk (10%), and middle childhood onset risk (19%). Pregnancy and delivery complications and harsh-intrusive caregiving behaviors operated as general risk for all ADHD profiles. Parental history of ADHD was uniquely predictive of early onset and persistent ADHD risk, and low primary caregiver education was uniquely predictive of early childhood limited ADHD risk. Results are discussed with respect to how changes to the age of onset criterion for ADHD in DSM5 may affect etiological research and the need for developmental models of ADHD that inform ADHD symptom persistence and desistance.

Using Repeated-Measures Data to Make Stronger Tests of the Association between Executive Function Skills and Attention Deficit/Hyperactivity Disorder Symptomatology in Early Childhood.

Theoretical models of Attention deficit/hyperactivity disorder (ADHD) have long implicated executive function (EF) skills as contributing to the etiology, maintenance, and changes in ADHD symptomatology over time. Although there is interest making within-person inferences (i.e., deficits in EF skills give rise to ADHD behaviors), most of the evidence has been derived from studies that conflated between- and within-person sources of variance. Here, we use repeated-measures data to test within-person association between EF skills and ADHD behaviors. Participants included 1160 children from the Family Life Project, an ongoing prospective longitudinal study of child development in low-income, nonmetropolitan communities. We tested the magnitude of the association between EF skills and ADHD behaviors when children were 3, 4, and 5 years old. Consistent with meta-analyses, unadjusted bivariate associations between EF and ADHD (which reflect combined between- and within-person variation) were of moderate magnitude (rs = -0.20 to -0.30). However, after controlling for all time-invariant, between-person sources of variation, the within-person associations between EF skills and ADHD behaviors were weak (ßs - 0.04 to -0.05, ps = 0.01). These results suggest that EF skills may contribute less prominently to ADHD behaviors in early childhood than is commonly assumed and provoke broader questions about developmental models of ADHD.

Speed and accuracy on the Hearts and Flowers task interact to predict child outcomes.

The current study tests whether accuracy and reaction time (RT) on the Hearts and Flowers (HF) task, a common assessment tool used across wide age ranges, can be leveraged as joint indicators of child executive function (EF) ability. Although previous studies have tended to use accuracy or RT, either alone or as separate indicators, one open question is whether these 2 metrics can be yoked together to enhance our measurement of EF ability. We test this question using HF data collected from first-grade children who participated in the Family Life Project. Specifically, we model the independent and interactive effects of HF accuracy and RT on several criterion outcomes representing child academic and behavioral competence. Our findings indicate that among early-elementary-aged children, accuracy and RT interact in the prediction of child outcomes, with RT being a more informative index of EF ability for children who perform at high levels of accuracy. The main effect of accuracy remained significant in the presence of these interactive effects. This pattern of findings was similar for different task blocks (i.e., mixed, flower-only) and for different child outcome domains (i.e., academic, behavioral). Our finding of an interaction between accuracy and RT contributes to a growing literature that attempts to jointly consider accuracy and RT as indicators of underlying ability, which has important implications for how EF task scores are constructed and interpreted. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Integrating Item Accuracy and Reaction Time to Improve the Measurement of Inhibitory Control Abilities in Early Childhood.

Efforts to improve children's executive function are often hampered by the lack of measures that are optimized for use during the transition from preschool to elementary school. Whereas preschool-based measures often emphasize response accuracy, elementary school-based measures emphasize reaction time (RT)-especially for measures inhibitory control (IC) tasks that typically have a speeded component. The primary objective of this study was to test in a preschool-aged sample whether the joint use of item-level accuracy and RT data resulted in improved scoring for three IC tasks relative to scores derived from accuracy data alone. Generally, the joint use of item-level accuracy and RT data resulted in modest improvements in the measurement precision of IC abilities. Moreover, the joint use of item-level accuracy and RT helped eliminate floor and ceiling effects that occurred when accuracy data were considered alone. Results are discussed with respect to the importance of scoring IC tasks in ways that are maximally informative for program evaluation and longitudinal modeling.

The benefits of adding a brief measure of simple reaction time to the assessment of executive function skills in early childhood.

Early childhood represents a period of rapid cognitive developmental change in executive function (EF) skills along with a variety of related cognitive processes, including processing speed. This leads to interpretational challenges in that children's performance on EF tasks reflects more than EF skills per se. We tested whether the inclusion of a brief measure of simple reaction time (SRT) during EF assessments could help to partially address this challenge. Data were drawn from a cross-sectional convenience sample of 830 preschool-aged children. Individual differences in SRT were significantly associated with performance on all tasks (R2s = .09-.26); slower performance on the SRT task was associated with poorer performance on each EF task. Age-related differences in individual EF tasks were reduced by approximately one half after accounting for age-related differences in SRT, and EF task scores were less coherent (i.e., less strongly intercorrelated with each other) after the removal of SRT. Age-related differences in EF were smaller (Cohen ds = 1.36 vs. 0.78), and poverty-related differences in EF were larger (Cohen ds = 0.30 vs. 0.46) after accounting for SRT-related variation. Finally, consistent with previous studies, SRT-related differences in fluid reasoning were mediated by EF skills. Results are discussed with respect to using a brief measure of SRT to partially address the problem of measurement impurity at the level of individual EF tasks.

The Childhood Executive Functioning Inventory (CHEXI): Factor structure, measurement invariance, and correlates in US preschoolers.

This study tests the factor structure, measurement invariance, and correlates of the Childhood Executive Functioning Inventory (CHEXI) with a large and diverse sample of 3- to 5-year-olds (n = 844). Consistent with previous studies, a two-factor model that distinguishes working memory from inhibition provides the best fit to the observed data. This two-factor model has been shown to demonstrate strong measurement invariance for different subgroups of children (boys vs. girls, high vs. low income). Whereas boys tend to have greater working memory and inhibition difficulties (Cohen's d = 0.15 and 0.20, respectively), children from low-income households tend to have more working memory problems than their peers from high-income households (Cohen's d = 0.25). Finally, correlations between CHEXI scores, examiner reports of child behavior, and child performance on a battery of executive function (EF) tasks were investigated. CHEXI scores were found to be more consistently related to examiner reports of child behavior than child performance on EF tasks. Tthe strengths and weaknesses of the CHEXI as a questionnaire measure of EF are discussed, and directions for future research are suggested.

Executive Function Buffers the Association between Early Math and Later Academic Skills.

Extensive evidence has suggested that early academic skills are a robust indicator of later academic achievement; however, there is mixed evidence of the effectiveness of intervention on academic skills in early years to improve later outcomes. As such, it is clear there are other contributing factors to the development of academic skills. The present study tests the role of executive function (EF) (a construct made up of skills complicit in the achievement of goal-directed tasks) in predicting 5th grade math and reading ability above and beyond math and reading ability prior to school entry, and net of other cognitive covariates including processing speed, vocabulary, and IQ. Using a longitudinal dataset of N = 1292 participants representative of rural areas in two distinctive geographical parts of the United States, the present investigation finds EF at age 5 strongly predicts 5th grade academic skills, as do cognitive covariates. Additionally, investigation of an interaction between early math ability and EF reveals the magnitude of the association between early math and later math varies as a function of early EF, such that participants who have high levels of EF can "catch up" to peers who perform better on assessments of early math ability. These results suggest EF is pivotal to the development of academic skills throughout elementary school. Implications for further research and practice are discussed.

Examining an Executive Function Battery for Use with Preschool Children with Disabilities.

Performance-based assessments of EF for use with young children who have or are at risk for disabilities are lacking. The current study investigates the use of a computerized battery for children with subclinical behaviors (N = 846) across a variety of developmental disabilities and evaluates practical information about feasibility of task administration. Results reveal that children with disabilities performed similarly to their typically developing peers across a variety of metrics for evaluating the battery, ranging from percent correct scores to administrator quality ratings. Thus, the battery may be considered an easy-to-administer, performance-based assessment tool in which children with disabilities do not perform systemically worse than typically developing peers.

Salivary cortisol and cognitive development in infants from low-income communities.

Early stress exposure is proposed to have significant lasting effects on cognitive development. The glucocorticoid hormone cortisol, a product of the hypothalamic-pituitary-adrenal (HPA) axis, is a particular focus of research, however, the majority of past research has been based on studies of older children and adults. Evidence linking cortisol levels in infancy with cognitive development is lacking. In a large cohort sample of infants (N = 1091) oversampled for psychosocial risk, we tested whether basal cortisol levels and cortisol reactivity to emotional stressors administered at 7 and 15 months of age were associated with cognitive development measured at 15 months. Cognitive development was measured using the Mental Development Index of the Bayley Scales of Infant Development. Multiple regression analyses indicated that basal cortisol levels at 15 months, and to a lesser extent at seven months, were inversely associated with infant cognitive development after adjusting for psychosocial and obstetric risk. The findings provide some of the first evidence that HPA axis activity in infancy is associated with early cognitive development.

Developmental Delays in Executive Function from 3 to 5 Years of Age Predict Kindergarten Academic Readiness.

Substantial evidence has established that individual differences in executive function (EF) in early childhood are uniquely predictive of children's academic readiness at school entry. The current study tested whether growth trajectories of EF across the early childhood period could be used to identify a subset of children who were at pronounced risk for academic impairment in kindergarten. Using data that were collected at the age 3, 4, and 5 home assessments in the Family Life Project ( N = 1,120), growth mixture models were used to identify 9% of children who exhibited impaired EF performance (i.e., persistently low levels of EF that did not show expected improvements across time). Compared to children who exhibited typical trajectories of EF, the delayed group exhibited substantial impairments in multiple indicators of academic readiness in kindergarten (Cohen's ds = 0.9-2.7; odds ratios = 9.8-23.8). Although reduced in magnitude following control for a range of socioeconomic and cognitive (general intelligence screener, receptive vocabulary) covariates, moderate-sized group differences remained (Cohen's ds = 0.2-2.4; odds ratios = 3.9-5.4). Results are discussed with respect to the use of repeated measures of EF as a method of early identification, as well as the resulting translational implications of doing so.

The test-retest reliability of the latent construct of executive function depends on whether tasks are represented as formative or reflective indicators.

This study investigates the test-retest reliability of a battery of executive function (EF) tasks with a specific interest in testing whether the method that is used to create a battery-wide score would result in differences in the apparent test-retest reliability of children's performance. A total of 188 4-year-olds completed a battery of computerized EF tasks twice across a period of approximately two weeks. Two different approaches were used to create a score that indexed children's overall performance on the battery-i.e., (1) the mean score of all completed tasks and (2) a factor score estimate which used confirmatory factor analysis (CFA). Pearson and intra-class correlations were used to investigate the test-retest reliability of individual EF tasks, as well as an overall battery score. Consistent with previous studies, the test-retest reliability of individual tasks was modest (rs ≈ .60). The test-retest reliability of the overall battery scores differed depending on the scoring approach (rmean = .72; rfactor_score = .99). It is concluded that the children's performance on individual EF tasks exhibit modest levels of test-retest reliability. This underscores the importance of administering multiple tasks and aggregating performance across these tasks in order to improve precision of measurement. However, the specific strategy that is used has a large impact on the apparent test-retest reliability of the overall score. These results replicate our earlier findings and provide additional cautionary evidence against the routine use of factor analytic approaches for representing individual performance across a battery of EF tasks.

The contribution of children's time-specific and longitudinal expressive language skills on developmental trajectories of executive function.

To investigate whether children's early language skills support the development of executive functions (EFs), the current study used an epidemiological sample (N=1121) to determine whether two key language indicators, vocabulary and language complexity, were predictive of EF abilities over the preschool years. We examined vocabulary and language complexity both as time-varying covariates that predicted time-specific indicators of EF at 36 and 60 months of age and as time-invariant covariates that predicted children's EF at 60 months and change in EF from 36 to 60 months. We found that the rate of change in children's vocabulary between 15 and 36 months was associated with both the trajectory of EF from 36 to 60 months and the resulting abilities at 60 months. In contrast, children's language complexity had a time-specific association with EF only at 60 months. These findings suggest that children's early gains in vocabulary may be particularly relevant for emerging EF abilities.

Measuring executive function in early childhood: A case for formative measurement.

This study tested whether individual executive function (EF) tasks were better characterized as formative or reflective indicators of the latent construct of EF. EF data that were collected as part of the Family Life Project (FLP), a prospective longitudinal study of families who were recruited at the birth of a new child (N = 1,292), when children were 3, 4, and 5 years old. Vanishing tetrad tests were used to test the relative fit of models in which EF tasks were used as either formative or reflective indicators of the latent construct of EF in the prediction of intellectual ability (at Age 3), attention-deficit hyperactivity disorder symptoms (at Ages 3 to 5 years), and academic achievement (at kindergarten). Results consistently indicated that EF tasks were better represented as formative indicators of the latent construct of EF. Next, individual tasks were combined to form an overall measure of EF ability in ways generally consistent with formative (i.e., creating a composite mean score) and reflective (i.e., creating an EF factor score) measurement. The test-retest reliability and developmental trajectories of EF differed substantially, depending on which overall measure of EF ability was used. In general, the across-time stability of EF was markedly higher when represented as a factor score versus composite score. Results are discussed with respect to the ways in which the statistical representation of EF tasks can exert a large impact on inferences regarding the developmental causes, course, and consequences of EF.

Early communicative gestures prospectively predict language development and executive function in early childhood.

Using an epidemiological sample (N = 1,117) and a prospective longitudinal design, this study tested the direct and indirect effects of preverbal and verbal communication (15 months to 3 years) on executive function (EF) at age 4 years. Results indicated that whereas gestures (15 months), as well as language (2 and 3 years), were correlated with later EF (φs ≥ .44), the effect was entirely mediated through later language. In contrast, language had significant direct and indirect effects on later EF. Exploratory analyses indicated that the pattern of results was comparable for low- and not-low-income families. The results were consistent with theoretical accounts of language as a precursor of EF ability, and highlighted gesture as an early indicator of EF.