Association between exposure to air pollution and thalamus volume in adults: A cross-sectional study

BACKGROUND: Air pollution has been associated with cognitive function and brain volume. While most previous research has examined the association between air pollution and brain volume in cortical structures or total brain volume, less research has investigated associations between exposure to air pollution and subcortical structures, including the thalamus. Further, the few available previous studies investigating associations between air pollution and thalamic volume have shown mixed results. METHODS: In this study, we evaluated the association between PM(2.5), PM(2.5–10), PM(10), nitrogen dioxide, and nitrogen oxides and volume of the thalamus in adults using the UK Biobank resource, a large community-based sample, while adjusting for multiple covariates that could confound an association between air pollution and thalamic volume. RESULTS: In adjusted models, the left but not right thalamus volume was significantly inversely associated with PM(2.5–10), although there were no significant associations between PM(2.5), PM(10), nitrogen dioxide, and nitrogen oxides with either left or right thalamic volumes. In addition, interactions between age and PM(2.5–10) and PM(10) were inversely associated with thalamic volume, such that thalamic volume in older people appeared more vulnerable to the adverse effects of PM(2.5–10) and PM(10), and interactions between educational attainment and PM(2.5), nitrogen dioxide, and nitrogen oxides and between self-rated health and PM(2.5–10) were positively associated with thalamic volume, such that higher educational attainment and better self-rated health appeared protective against the adverse effects of air pollution on the thalamus. CONCLUSION: These findings suggest a possible association between thalamic volume and air pollution particularly in older people and in people with comparatively low educational attainment at levels of air pollution found in the United Kingdom.