Early-life urban exposome and brain structural connectivity and morphology in preadolescents

Abstract

Recent studies have linked air pollution to brain characteristics in children, but few studies have considered associations with other urban exposures. We investigated the associations between urban exposome and white matter microstructure and brain volumes in preadolescents. We used data from 3,315 children of the Generation R cohort, The Netherlands. Residential levels of 20 built environment metrics, 6 natural spaces indicators, 12 air pollutants, and road-traffic noise were assessed during pregnancy and childhood. Diffusion tensor and structural brain images were obtained at 9–12 years. We estimated fractional anisotropy (FA) and mean diffusivity (MD) and several brain structure volumes. We ran multi-pollutant analysis between built environment and natural spaces indicators and each outcome using Deletion/Substitution/Addition algorithm. When an association was found, we ran mediation analyses to estimate whether the association was mediated by air pollution or noise. Built environment and natural spaces indicators during pregnancy were not associated with FA nor MD. During childhood, building density and industrial or commercial land use (LU) were related to higher MD, and LU diversity was associated with lower MD (e.g., -0.02 95%CI (0,03; -0,01)). Total effects of building density and LU diversity were partially mediated by fine particulate matter elemental zinc (9.0% and 23.2%, respectively). Surrounding greenness during pregnancy was associated with smaller subcortical gray matter, pallidum and thalamus volumes, with no mediation by air pollution nor noise. Built environment indicators, including LU diversity and unhealthy food facilities density during pregnancy or childhood were associated with smaller hippocampus, larger amygdala and nucleus accumbens volumes, with a mediation up to 6.9% by elemental zinc or polycyclic aromatic hydrocarbons. Early-life built environment and natural space indicators were related to brain structural connectivity and morphology in preadolescence, with a partial mediation by air pollution levels. Birth cohort, urban exposome, air pollution, natural spaces, neuroimaging, child development