Early Childhood Socioeconomic Status and Cognitive and Adaptive Outcomes at the Transition to Adulthood: The Mediating Role of Gray Matter Development Across Five Scan Waves

Abstract

Background: Early low socioeconomic status (SES) is associated with poor outcomes in childhood, many of which endure into adulthood. It is critical to determine how early low SES relates to trajectories of brain development and whether these mediate relationships to poor outcomes. We use data from a unique 17-year longitudinal study with five waves of structural brain imaging to prospectively examine relationships between preschool SES and cognitive, social, academic, and psychiatric outcomes in early adulthood.

Methods: Children (n = 216, 50% female, 47.2% non-White) were recruited from a study of early onset depression and followed approximately annually. Family income-to-needs ratios (SES) were assessed when children were ages 3 to 5 years. Volumes of cortical gray and white matter and subcortical gray matter collected across five scan waves were processed using the FreeSurfer Longitudinal pipeline. When youth were ages 16+ years, cognitive function was assessed using the NIH Toolbox, and psychiatric diagnoses, high-risk behaviors, educational function, and social function were assessed using clinician administered and parent/youth report measures.

Results: Lower preschool SES related to worse cognitive, high-risk, educational, and social outcomes (|standardized B| = 0.20-0.31, p values < .003). Lower SES was associated with overall lower cortical (standardized B = 0.12, p < .0001) and subcortical gray matter (standardized B = 0.17, p < .0001) volumes, as well as a shallower slope of subcortical gray matter growth over time (standardized B = 0.04, p = .012). Subcortical gray matter mediated the relationship of preschool SES to cognition and high-risk behaviors.

Conclusions: These novel longitudinal data underscore the key role of brain development in understanding the long-lasting relations of early low SES to outcomes in children.

Keywords: Adaptive function; Brain development; Cognition; Risk-taking; Social function; Socioeconomic status.

Figure 1:. Trajectories of Cortical and Subcortical Gray Matter as a Function of T1 Income-to-needs Ratio.

A) Trajectory of cortical gray matter, with the estimated fit lines plotted separately for the mean T1 income-to-needs and +/− 1 standard deviation; B) Trajectory of subcortical gray matter, with the estimated fit lines plotted separately for the mean T1 income-to-needs and +/− 1 standard deviation. These graphs were generated using the original values for interpretation, though the analyses were run on standardized variables. Mean values of 0.5 (neutral) for sex and 1547.9 cm³ for intracranial volume were entered into the model equation.

Figure 2:. Mediation Models for Subcortical Gray Matter Volumes.

Mediation results were generated using the PROCESS 3.5 macro in R version 4.03, beta 0.5. The “a” values refer to the relationship between the predictor and the mediator, and the “b” values refer to the relationship the mediator and the outcome. The “c” values are the direct relationship between the predictor and the outcome with no mediator in the model, and the “c’” values are the relationships between the predictor and the outcome with the mediator in the model.

Figure 3:. Graphs Illustrating Bivariate Relationships Subcortical Gray Matter Volumes.

A) Scatterplot depicting the relationship between T1 income-to-needs and the slope of subcortical gray matter volume, with the estimated linear fit and 95% confidence interval overlayed. B) Scatterplot depicting the relationship between the slope of subcortical gray matter volume and cognitive function, with the estimated linear fit and 95% confidence interval overlayed. C) Scatterplot depicting the relationship between the slope of subcortical gray matter volume, and high-risk behaviors with the estimated linear fit and 95% confidence interval overlayed.