Thread by @AdrianZhaolong

Both neighborhood and family #socioeconomic status (SES) influence children’s gray matter structure & function, but what about #whitematter (WM)? What could be some mediating mechanisms? We studied these questions in 8842 children from the #ABCD Study: medrxiv.org/content/10.110…

RSI assessed microstructure in 31 WM tracts. We looked at RND, which measured *directional* intracellular water & could reflect organized #myelin, and RNI, which measured *isotropic* intercellular water & could reflect #glia/neuron cell bodies. (fig adapted Burnor et al 2021)

Higher neighborhood disadvantage and lower parental education had independent links to lower RND (organized myelin) in forceps maj, corticospinal tract, and sup long fasciculus. These agree with previous findings of lower DTI-FA and lower WM integrity in low SES.

Lower household income was associated with greater RNI (glial/neuronal cell presence), in almost every tract! Higher neighborhood disadvantage had independent links to greater RNI in frontolimbic tracts. Parental education had an independent, unique effect in forceps major.

What are some proximal factors that may link SES to the brain? We first looked at #obesity. Childhood obesity is on the rise, more prevalent in low-SES groups, and associated with negative brain and health outcomes.

Higher BMI was an indirect effect in the links between low SES and higher RNI. This may reflect the neuroinflammatory phenotype (eg microglial activation) seen in childhood obesity, or stress/adversity-related accelerated development that has also been noted in obesity.

Higher BMI also mediated links between low SES and lower RND. This aligns with WM/axonal damage in obesity-related #inflammation.

We then looked at #cognitive performance. Some recent studies suggested that it could reflect sensory/cognitive/social stimulation in the environment, which is influenced by SES and is important for WM development.

Higher total cognition score (from NIH Toolbox) had an indirect effect on the links between high SES and higher RND. This is consistent with reports of higher DTI-FA and WM integrity linked to enriching activities, like music, play, reading, etc.

However, we couldn’t infer directionality per cross-sectional data, and we also found RND to mediate between SES and cognition. “Cognitive performance” is likely a mix of environmental (enrichment) and biological (brain-based fxn) influences. Future works should dissociate them.

Critically, our mediation models showed independent effects at neighborhood & household levels, so interventions should be considered from multiple SES angles. Also, many community/personal health choices are filtered thru structural barriers, and #socialpolicy support is vital.

This is the largest study on SES and WM microstructure in children. Low SES seems related to lower myelin organization and higher glia/neuron presence. Obesity and environmental enrichment may be intervention targets to help promote #brain #health in disadvantaged children.

Huge thanks to amazing mentors Drs Tamara Hershey and @smarek0502 and great co-authors @ShirleyYuqiCai Rita Taylor and Drs @BarchDbarch and Sarah Eisenstein!

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