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BACKGROUND: Exposure to air pollution has been suggested to increase the risk of dementia, but studies on this link often lack a detailed screening for dementia and data on important confounders.

OBJECTIVE: To determine the association of exposure to air pollution with the risk of dementia and cognitive decline in the population-based Rotterdam Study.

METHODS: Between 2009 and 2010, we determined air pollutant concentrations at participants residential addresses using land use regression models. Determined air pollutants include particulate matter <10μm (PM10) and <2.5μm (PM2.5), a proxy of elemental carbon (PM2.5 absorbance), nitrogen oxide (NOx), and nitrogen dioxide (NO2). As the individual air pollutant levels were highly correlated (r = 0.71-0.98), we computed a general marker covering all air pollutants based on a principal component analysis. We followed participants up for dementia until 2018 and determined cognitive performance during two subsequent examination rounds. Using Cox and linear mixed models, we related air pollution to dementia and cognitive decline.

RESULTS: Of the 7,511 non-demented participants at baseline, 545 developed dementia during a median follow-up of 7 years. The general marker of all air pollutants was not associated with the risk of dementia (hazard ratio [95% confidence interval]: 1.04 [0.95-1.15]), neither were the individual air pollutants. Also, the general marker of all air pollutants or the individual air pollutant levels were not associated with cognitive decline.

CONCLUSION: In this study, we found no clear evidence for an association between exposure to air pollution and the risk of dementia or cognitive decline.