Outdoor residential air pollution exposure and the development of brain volumes across childhood: A longitudinal study

Emerging evidence suggests that air pollution exposure is associated with child's brain morphology, but the relationship between air pollution and longitudinal changes in the development of brain volumes has yet to be investigated. We studied the association of exposure to air pollution in pregnancy and childhood with the change of brain volumes from childhood into adolescence, using repeated assessments of brain volumes. We used data from 4243 children of a large Dutch population-based birth cohort. Exposure to 14 air pollutants during pregnancy and childhood was estimated using land-use regression models. We obtained structural brain MRI data at 3 timepoints, resulting in 6059 useable scans of white matter, cortical grey matter, cerebellum, and 7 subcortical volumes. For 1191 participants we had data on both last two timepoints. We conducted single-pollutant analyses for each air pollutant and brain volume, using linear mixed models adjusted for life-style and socioeconomic status variables. Then we performed multi-pollutant analyses with the least absolute shrinkage and selection operator for mixed models. Air pollution exposure was not associated with changes in white matter, cortical grey matter, and cerebellar volumes. Higher exposure to copper and particulate matter with aerodynamic diameter <2.5 μm (PM_2.5) during pregnancy was associated with a smaller hippocampal volume at the first neuroimaging assessment, followed by faster growth of hippocampal volume (e.g. 25.1 mm³ increase of hippocampal volume [95 % CI 8.6; 41.7] per 5 ng/m³ increase in copper exposure per year of age). Results were comparable when restricting the analyses to children with complete data for the last two timepoints. Exposure to copper and PM_2.5 during pregnancy was related with a smaller hippocampal volume in mid childhood, followed by catch-up growth. Plasticity of the hippocampus might mitigate adverse effects of air pollution early in life.