Long-term exposure to atmospheric metals and cognitive performance in rural and semi-urban areas in the Constances cohort

The role of exposure to PM2.5 components on cognitive impairment remains poorly understood. Atmospheric metals are of particular concern, as some are known neurotoxins. However, the effect of their exposure on cognition are not well known. This cross-sectional study aims to study the associations between a set of atmospheric metals and cognitive performances in adults. Our analyses included 45,162 semi-urban and rural participants of the French Constances cohort aged over 45 years old at inclusion. We estimated residential exposure to atmospheric metals using moss biomonitoring data spatially interpolated by ordinary kriging. After a rotated principal component analysis (PCA), we derived three groups of metals and identified one as anthropogenic which included cadmium (Cd), lead (Pb), zinc (Zn), antimony (Sb) and copper (Cu). We assessed cognitive impairment using a battery of six tests covering three cognitive domains (episodic memory, executive functions, language) and cognitive norms previously defined by age, sex and education. We used logistic regression models to analyze the association between the anthropogenic group and each metal and each cognitive test. Median exposures ranged between 0.09 (interquartile range (IQR): 0.05) for Sb, and 30.5 (IQR: 8.6) for Zn μg/g of dried moss. Exposure to atmospheric metals was associated with poorer cognitive performance for at least one of the domains. For instance, we found that exposure to Pb was associated with poorer executive functions (TMT-A score), with an odds ratio (OR) of 1.15 (1.09: 1.21) for an IQR increase, and significant positive but nonlinear associations with the PCA anthropogenic group. For semantic skills, we found a statistically significant association only for Cu (OR=1.04 (1.00: 1.08) for an IQR increase). For lexical skills and episodic memory, associations were either non-linear with no clear trend, or protective. Further research on the subject is required, especially in urban settings and using longitudinal designs.