Mendelian randomization study supports the causal effects of air pollutants on cognitive function

Observational studies have linked air pollutants to cognitive impairment, though the causal relationship is yet to be firmly established. This research employs a two-sample Mendelian randomization (MR) analysis to evaluate the causal effects of exposure to PM_2.5, PM₁₀, NO₂, and NO_x on cognitive function. This study extracted 8 single nucleotide polymorphisms (SNPs) associated with PM_2.5, 22 SNPs associated with PM₁₀, 7 SNPs associated with NO₂ and 8 SNPs associated with NO_x as genetic variants on European ancestry. The primary method for MR estimation utilized was inverse variance weighting (IVW). The findings indicate that exposure to PM_2.5 results in poorer performance on the Trail Making Test (beta = 0.24, 95 % CI: 0.01 to 0.47, P = 0.04). Exposure to NO_x is associated with a decline in fluid intelligence (beta = −0.88, 95 % CI: 1.42 to −0.34, P = 0.002). Additionally, each standard deviation increase in NO_x exposure is linked to a decrease in the number of correct matches (beta = −0.39, 95 % CI: 0.73 to −0.05, P = 0.02) and attempted matches (beta = −0.40, 95 % CI: 0.74 to −0.05, P = 0.02) on the Symbol Digit Substitution (SDS) test, and an increase in the time taken to enter a value (beta = 0.41, 95 % CI: 0.06 to 0.76, P = 0.02). Furthermore, a positive association was observed between PM₁₀ exposure and the risk of Alzheimer's disease (OR = 2.15, 95 % CI: 1.14 to 4.03, P = 0.02). This study suggests that PM₁₀ is causally associated with Alzheimer's disease risk. Genetically PM_2.5 and NO_x exposure showed a significant association with cognitive decline in people of European origin. Air pollutants is important for developing effective prevention strategies for cognitive decline.