Association of exposure to ambient air pollutants with cognitive performance and dementia risk and the mediating role of pulmonary function: Evidence from the UK Biobank

Abstract Background The pathways by which air pollution affects cognition remain to be explored. This study aimed to explore how single air pollutants [including nitrogen oxide (NOX), nitrogen dioxide (NO2), particulate matter with a diameter of 2.5 micrometers (PM2.5), PM10, and PM2.5–10], and air pollution mixture could affect cognitive function and the incidence of dementia, and determine whether pulmonary function (PF) could play a mediating role in the relationship. Methods Multiple statistical methods were employed to evaluate association of 5 air pollutants (NOX, NO2, PM2.5, PM10, and PM2.5–10) with cognitive function. Bootstrap method was used to estimate mediating role of PF in the association of air pollutants with cognition or the incidence of dementia. Results A mixture of air pollutants was associated with performance on 5 cognitive tests, and global cognition (p < .05). Significantly negative association was also identified between mixture of air pollutants and PF (β= −0.020, 95% confidence interval (CI) = −0.029 to −0.011). In addition, as PF scores increase, performance on all cognitive tests significantly improve, although the risk of dementia correspondingly decreases. It was noted that PF was shown to mediate the effects of air pollution mixtures on all cognitive tests as well as global cognition. For global cognition, PF mediated 6.08% of the association. PF was also found to have a mediating role in the association between NOX, NO2, PM2.5, and the risk of dementia. Conclusions Mixed air pollution may impact cognitive function, with PF potentially mediating this relationship.