Background: Sex difference in the association between ambient air pollution and cognitive aging remained unclear. This current study aimed to assess the impacts of long-term exposure to major air pollutants on cognitive performance among Chinese middle-aged and older adults, and explore whether these associations could be modified by sex.
Methods: By deriving longitudinal data from four waves of the China Health and Retirement Longitudinal Study, we included 13,507 participants aged 45+ years who had at least two cognitive tests recorded from 2011 to 2018. We used a standardized questionnaire consisting of five domain-specific functions to measure global cognitive score. Based on well-validated spatiotemporal datasets, annual average concentrations of ambient fine particulate matter (PM2.5), nitrogen dioxide (NO2), and ozone (O3) were assigned to each enrollee at prefectural city level and at the simulated residential addresses through Monte Carlo simulation approach. Linear mixed-effects models were applied to assess the impacts of major air pollutants on cognitive function with multiple adjustments. Sex-stratified analyses were performed to examine the potential effect modification on these associations. To enhance the interpretability of our results, we also compared the estimated effects of air pollutants with the effect of aging on cognitive function.
Results: We evaluated 38,950 records of cognitive function tests, of which 44.0% were from women. An increase of 10-μg/m3 in PM2.5, NO2 and O3 exposure were associated with 0.36 (95% confidence interval: -0.40, -0.31), 0.51 (-0.60, -0.43) and 0.26 (-0.47, -0.06) points decline in global cognitive score, respectively, equivalent to the effect of aging by 2.8-5.0 years. Sex-stratified analyses suggested significantly greater cognitive impairment associated with air pollutants in women than men. We found reversely J-shaped concentration-response relationships between ambient air pollutants and cognitive decline in both sexes. Main findings on sex-specific associations were robust to the adjustments for covariates, inclusion criteria, and co-pollutant analyses, as well as sensitivity analyses based on simulation-based exposure for PM2.5 and NO2.
Conclusions: Later-life exposure to ambient air pollution may accelerate cognitive aging of middle-aged and older adults, suggesting significant sex disparity with higher vulnerability in women.
Keywords: Aging; Air pollution; CHARLS; Cognitive function; Sex disparity.
Copyright © 2023. Published by Elsevier B.V.