Association of ambient air pollution with cognitive functioning and markers of structural brain damage: The Maastricht study

INTRODUCTIONGiven the absence of curative interventions and the rising global incidence of dementia, research is increasingly focusing on lifestyle factors for prevention. However, identifying shared environmental risk for dementia, next to individual factors, is crucial for optimal risk reduction strategies. Therefore, in the present study the association between air pollution, cognitive functioning, and markers of structural brain damage was investigated.METHODSWe used cross-sectional data from 4,002 participants of The Maastricht Study on volumetric markers of brain integrity (white and grey matter volume, cerebrospinal fluid volume, white matter hyperintensities volume, presence of cerebral small vessel disease) and cognitive functioning. Individuals were matched by postal code of residence to nationwide data on air pollution exposure (PM2.5, PM10, NO2, soot). Potential linear and non-linear associations were investigated with linear, logistic, and restricted cubic spline regression and adjusted for demographic characteristics and a compound score of modifiable dementia risk and protective factors.RESULTSExposure to air pollutants was not related to cognitive functioning and most brain markers. We found curvilinear relationships between high PM2.5 exposures and grey matter and cerebrospinal fluid volume. Participants in the mid- to high-range of exposure (12.14μg/m3 to 15.48μg/m3) had lower grey matter volume and higher cerebrospinal fluid volume than those exposued to lower levels of pollution, independent of demographic and individual modifiable dementia risk factors. In the low- to mid-range exposure (10.08μg/m3 to 12.14μg/m3) participants had higher grey matter volumes. After additional post hoc analyses, controlling for urbanicity, the associations for grey matter volume became non-significant. In men only, higher exposure to all air pollutants was associated with lower white matter volumes. No significant associations with white matter hyperintensities volume or cerebral small vessel disease were observed.DISCUSSIONOur findings suggest that PM2.5 exposure in the mid-to high range is associated with more brain atrophy.