Julia Anglen Bauer

Background: Child-centred approaches represent a conceptual framework that emphasises the holistic characterisation of individual developmental patterns across cognitive, behavioural and social domains. As a complementary analytic tool, self-organising maps (SOMs), an artificial neural network, offer flexible, data-driven clustering capabilities that are well-suited to modeling complex, multidimensional and longitudinal developmental data. Despite their potential, few studies have applied such methods to profile early neurodevelopment, especially in rural populations. Methods: We applied SOM to longitudinal neurobehavioural data (n=235) from healthy participant children from 3 to 5 years of age in the New Hampshire Birth Cohort Study, a rural pregnancy cohort. Group profiles reflect measures of behaviour and social responsiveness, cognition and motor performance and were examined in relation to known predictors of maternal-child characteristics using multinomial logistic regression as a proof of concept. Results: In our cohort, most children had neurotypical neurobehavioural scores, and 51% were boys. Mothers predominantly had some college education (74%), were married (93%) and were 31 years of age on average with above-average IQs relative to US norms. We identified six distinct neurobehavioural profiles (18–57 children each). The six profiles included: highest overall scores (profile 5), worst overall scores (profile 4), greatest behavioural/social improvement (profile 1), slight improvement (profile 3), average scores (profile 2) and highest adaptability (profile 6) relative to the full sample. Regression models showed expected associations with child sex, maternal IQ and parent-child relationships (eg, higher maternal IQ correlated with better cognitive outcomes). Conclusions: Using a SOM, we identified distinct neurobehavioural profiles among rural children, reflecting variation across behaviour, social responsiveness, cognition and motor skills. These profiles varied by maternal and child characteristics and highlight the potential of neural network approaches to inform early risk or resilience identification in understudied populations.

A child’s exposure to arsenic (As) can begin in utero through placental transfer to the fetus. There is a growing body of epidemiologic evidence suggesting an association between As exposure and neuropsychological development. Therefore, our objective was to describe the consequences of maternal and/or childhood As exposure on children’s neuropsychological development. We conducted a scoping review with a systematic search of the PubMed, Scopus, EMBASE, Web of Science, and PsycINFO databases. We included studies that assessed the association between maternal and/or childhood As exposure and neuropsychological development in children up to an average of 12 years of age. A total of 77 studies were included, most of which were published between 2020 and 2024 (44.1%), conducted in the United States of America (18.2%) and Bangladesh (16.9%), and involved participants with a median age of 6.6 years. Most studies performed cross-sectional analyses (51.9%) and assessed exposure to elements other than As (64.9%). Childhood was the most frequently studied exposure window (57.2%), and urine was the most commonly used biomarker of exposure (58.4%), followed by blood or serum (32.3%). Cognition was the most frequently evaluated neuropsychological domain (94.8%), followed by psychomotor function (40.3%) and social–emotional function (29.9%). Most studies reported evidence of a negative impact of As exposure on children’s neuropsychological development (73.7%), while some found no changes (27.3%) and a few suggested an improvement (1.3%). An important limitation is that most studies measured total urinary As without speciation into inorganic versus organic forms, which limits the validity of dose–response conclusions based on total arsenic concentrations. This review highlights the potential deleterious neuropsychological effects of maternal and/or childhood As exposure while also identifying areas where the evidence remains inconclusive.

Research on the neurodevelopmental effects of metal(loid)s has focused mainly on outcomes assessed at one time point, even though brain development progresses over time. We investigated biomarkers of perinatal exposure to metals and changes in child behavior over time. We followed 268 participants from the prospective New Hampshire Birth Cohort Study between birth and age 5 years. We measured arsenic (As), copper (Cu), manganese (Mn), lead (Pb), selenium (Se), and zinc (Zn) in toenails from 6-week-old infants. The Behavioral Symptoms Index (BSI), externalizing, and internalizing symptoms were assessed using the Behavior Assessment System for Children, 2nd edition (BASC-2) at ages 3 and 5 years. Multivariable linear regression was used to estimate associations of metals with behavior change, calculated as the difference in symptom raw scores between 3 and 5 years, in addition to the associations for symptom scores at 3 and 5 years separately. Sex-specific associations were also explored using stratified models and a sex-metal interaction term. Adjusted associations of metals and change in behavior varied by exposure and outcome. Each 1 µg/g increase in ln toenail Cu was associated with improved behavior between 3 and 5 years [BSI: β = − 3.88 (95%CI: − 7.12, − 0.64); Externalizing problems: β = − 2.20 (95%CI: − 4.07, − 0.33)]. Increasing Zn was associated with increased externalizing behavior over time (β = 3.42 (95%CI: 0.60, 6.25). Sex-stratified analyses suggested more pronounced associations among boys compared to girls. Perinatal exposure to metals may alter behavioral development between ages 3 and 5 years. Findings support the need for more research on associations between metals and neurodevelopment over longer time periods.

Background Research on the neurodevelopmental effects of metal/metalloids has focused mainly on outcomes assessed at one time point, even though brain development progresses over time. We investigated biomarkers of perinatal exposure to metal/loids and changes in child behavior over time. Methods We followed 268 participants from the prospective New Hampshire Birth Cohort Study between birth and age five years. We measured arsenic (As), copper (Cu), manganese (Mn), lead (Pb), selenium (Se) and zinc (Zn) in toenails from 6-week-old infants. The Behavioral Symptoms Index (BSI), externalizing, and internalizing symptoms were assessed using the Behavior Assessment System for Children, 2nd edition (BASC-2) at ages 3 and 5 years. Multivariable linear regression was used to estimate associations of metal/loids with behavior change, calculated as the difference in symptom raw scores between 3 and 5 years, in addition to the associations for symptom scores at 3 and 5 years separately. Sex-specific associations were also explored using stratified models and a sex-metal interaction term. Results Adjusted associations of metal/loids and change in behavior varied by exposure and outcome. Each 1 µg/g increase in toenail Cu was associated with improved behavior between 3 and 5 years [BSI: β= -3.88 (95%CI: -7.12, -0.64); Externalizing problems: β = -2.20 (95%CI: -4.07, -0.33)]. Increasing Zn was associated with increased externalizing behavior over time (β = 3.42 (95%CI: 0.60, 6.25). Sex-stratified analyses suggested more pronounced associations among boys compared to girls. Conclusions Perinatal exposure to metal/loids may alter behavioral development between ages 3 and 5 years. Findings support the need for more research on associations between metal/loids and neurodevelopment over longer time periods.

Iron is needed for normal development in adolescence. Exposure to individual environmental metals (e.g., lead) has been associated with altered iron status in adolescence, but little is known about the cumulative associations of multiple metals with Fe status. We used data from the 2017–2018 National Health and Nutrition Examination Survey (NHANES) to examine associations between a metal mixture (lead, manganese, cadmium, selenium) and iron status in 588 U.S. adolescents (12–17 years). We estimated cumulative and interactive associations of the metal mixture with five iron status metrics using Bayesian Kernel Machine Regression (BKMR). Higher concentrations of manganese and cadmium were associated with lower log-transformed ferritin concentrations. Interactions were observed between manganese, cadmium, and lead for ferritin and the transferrin receptor, where iron status tended to be worse at higher concentrations of all metals. These results may reflect competition between environmental metals and iron for cellular uptake. Mixed metal exposures may alter normal iron function, which has implications for adolescent development.