The role of air pollution and lung function in cognitive impairment

Air pollution has been associated with impaired lung and cognitive function, especially impairment in visuo-construction performance (VCP). In this article, we evaluate whether the effect of air pollution on VCP is mediated by lung function. We used data from the SALIA cohort (baseline 1985-1994 and follow-up 2007-2010) including 587 women aged 55 years at baseline. Particulate matter (PM) and nitrogen dioxide (NO2) exposures at baseline were estimated via land-use regression models. Lung function was characterised by averages between baseline and follow-up. We used age-and height-controlled Global Lung Initiative (GLI) z-scores of forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC) and FEV1/FVC. VCP was assessed at follow-up with the CERAD-Plus neuropsychological test battery and causal mediation analysis was conducted. An increase of one interquartile range in FEV1 and FVC was positively associated with VCP (beta=0.18 (95% CI 0.02-0.34) and beta=0.23 (95% CI 0.07-0.39), respectively). The proportion of the association between NO2 on VCP mediated by FEV1 was 6.2% and this was higher in never smokers (7.2%) and non-carriers of the APOE-epsilon 4 allele (11.2%). However, none of the mediations were statistically significant. tIn conclusion, air pollution associated VCP was partially mediated by lung function. Further studies on the mechanisms underlying this pathway are required to develop new strategies to prevent air pollution induced cognitive impairment.