Table 1.
Demographics for the Adolescent Brain Cognitive Development (ABCD) study.
Fig 1.
Associations of risk of lead exposure and area deprivation index with subcortical volume.
Subcortical regions are sorted vertically by p-value (uncorrected) for risk of lead exposure. For each predictor (risk of lead exposure, area deprivation index), the shade of each cell reflects the strength of the association, with redder colors reflecting more positive associations and bluer colors reflecting more negative associations, in accordance with Fig 2. Analyses controlled for age, sex, parental education, race, ethnicity, family income, intracranial volume, and the interaction between family income and either lead risk or ADI. t(8508) = t-statistic, 8508 degrees of freedom. b = unstandardized regression coefficient (i.e., change in mm3 regional volume with decile of lead risk or area deprivation index).
Fig 2.
Regional associations between subcortical volume and risk of lead exposure (top) or area deprivation index (ADI) (bottom). For lead risk, these associations, correcting for false-discovery rate (FDR), were significant for mid-posterior, central, and mid-anterior corpus callosum. For ADI, subcortical gray matter, cerebellum cortex, accumbens area (not shown in this image), and amygdala. Regions are color-coded in correspondence to the effect size (i.e., partial correlation coefficient) of lead risk (top) and ADI (bottom), controlling for age, sex, parental education, race, ethnicity, family income, intracranial volume, and the interaction between family income and either lead risk or ADI. Regions with bolded outlines passed FDR correction. Blue-shaded regions indicate inverse associations between lead risk (or ADI) and volume (e.g., greater lead risk, lesser volume), while red-shaded regions indicate positive correlations (e.g., greater lead risk, greater volume). These images were generated in MATLAB using data from the ggseg toolbox in R [57]. 3v = 3rd ventricle; 4v = 4th ventricle; Am = amygdala; Bs = brain stem; C = caudate; CCa = anterior corpus callosum; CCc = central corpus callosum; CCma = mid-anterior corpus callosum; CCmp = mid-posterior corpus callosum; CCp = posterior corpus callosum; CeCo = cerebellum cortex; CeWm = cerebellum white matter; H = hippocampus; Lv = lateral ventricle; Pa = pallidum; P = putamen; Th = thalamus; V = ventral diencephalon.
Fig 3.
Posterior, mid-posterior, central, and mid-anterior corpus callosal volume significantly decreased with increasing risk of environmental lead exposure.
These inverse associations were not significantly different between children from low-, mid-, and high-income families. Error bars represent ±1 between-subjects standard error of the observed means. The solid lines represent means of the marginal fitted values of the model; the shaded area surrounding the solid lines represent ±1 between-subjects standard error of those means. Age, sex, parental education, race, ethnicity, and intracranial volume were included as covariates in this analysis.
Fig 4.
Mediational analyses showing indirect associations of lead risk on cognitive performance through mid-posterior corpus callosal (CC) volume.
The title of each row [e.g., “Executive Function (Card Sorting)”] refers to the construct and task used to assess that construct. The shading of the callosal regions, the mediator boxes (e.g., Mid-Posterior CC, Central CC), and histograms reflect the strength of the indirect association (per the color bar in the lower left corner). Callosal regions in dark gray were not incorporated as mediators in the corresponding analysis. Total effects of lead risk are represented by c, direct effects of lead risk are represented by c’, and a and b values refer to the associations of lead risk on callosal volume and callosal volume on cognitive performance, respectively. The subscript of the a and b values refer to the callosal subregion (i.e., C = central, MA = mid-anterior, MP = mid-posterior). All a, b, c, and c’ values are unstandardized regression coefficients. Thick arrows designate significant associations. Thin arrows designate non-significant associations. The presence of the statistical significance of indirect associations was determined by construction of bias-corrected percentile bootstrapping 95% confidence intervals (i.e., 10,000 bootstrapped samples), irrespective of the statistical significance of the corresponding total effect. The distributions of these bootstrapped indirect associations are shown, along with the original-sample indirect associations and corresponding confidence intervals. Bolded font indicates statistically significant indirect associations. Age, sex, parental education, race, ethnicity, and family income were included as covariates in analyses. Card Sorting = Dimensional Change Card Sort Task. Picture Vocabulary = Picture Vocabulary Test. Oral Reading = Oral Reading Recognition Test. Pattern Comparison = Pattern Comparison Processing Speed Test. Flanker = Flanker Inhibitory Control and Attention Test.