causal effects of air pollution on dementia: a mendelian randomized study

Abstract Background The 2017 Lancet Commission on Dementia Prevention, Intervention and Care included air pollution in the list of potential risk factors for dementia. Air pollution has been associated with an increased risk of dementia in observational studies, but the causal relationship remains unclear. In this study, we used a two‐sample Mendelian randomisation (MR) analysis to assess the causal relationship between PM 2.5 , PM 10 , NO 2 and NO X exposure and the occurrence of dementia, including Alzheimer’s disease (AD), vascular dementia, Lewy body dementia, and frontotemporal dementia. Method We extracted 5 single nucleotide polymorphisms associated with PM 2.5 , 22 single nucleotide polymorphisms associated with PM 10 , 6 single nucleotide polymorphisms associated with NO 2 and 8 single nucleotide polymorphisms associated with NO X as instrumental variables from a genome‐wide association study based primarily on European ancestry. Summary‐level statistics were obtained from the Dementia GWAS database and the FinnGen consortium. MR estimation was based on the inverse variance weighting (IVW) method as the primary method, supplemented by the MR‐Egger and weighted median (WM) methods. Finally, multiple validity tests and sensitivity analyses were performed to obtain robust and valid estimates. Result According to the IVW method, we found a positive association between PM 10 and AD risk (OR: 2.03, 95% CI: 1.06‐ 3.89, p = 0.03); NO 2 may increase the risk of AD (OR: 14.41, 95% CI: 10.95‐ 18.97, p = 0.04). However, there is insufficient evidence that PM 2.5 and NO X are associated with an increased risk of future dementia. Conclusion Our study suggests that PM 10 and NO 2 are causally associated with AD risk. PM 10 and NO 2 may increase the risk of AD in people of European origin. More animal experiments or population‐based observational studies with long follow‐up are needed in the future to explore the intrinsic mechanisms of PM 10 , NO 2 and AD.