Air quality improvement and cognitive function benefit: Insight from clean air action in China

Introduction: Epidemiological evidence suggests associations between long-term exposure to air pollution and accelerated cognitive decline. China implemented a strict clean air action plan in 2013; however, it is unclear whether the improvement of air quality has alleviated cognitive impairment in the population. Methods: From the China Health and Retirement Longitudinal Study, 8536 Chinese adults were enrolled in 2011 and followed up in 2015. Satellite-based spatiotemporal models were used to estimate exposure to air pollutants (including particles with diameters <= 1.0 mu m [PM1], <= 2.5 mu m [PM2.5], <= 10 mu m [PM10], nitrogen dioxide [NO2], and ozone [O-3]). Cognitive function was evaluated using a structured questionnaire in three dimensions: episodic memory, orientation and attention, and visuoconstruction. The associations between changes in the levels of air pollutants and cognitive function were elucidated by a logistic model. The Bayesian Kernel Machine Regression (BKMR) model was applied to evaluate the cumulative effect of air pollutants. Results: The mean (standard deviation) age of all participants was 58.6 (8.7) years. The odds ratio (95% confi-dence interval) between the highest and the lowest quartile of PM1 exposure reduction for cognitive impairment was 0.46 (0.41, 0.53) after adjusting for confounders. Similar protective effects of cognitive function were observed with the decrease in the level of PM2.5 (0.34 [0.30, 0.39]), PM10 (0.54 [0.48, 0.62]), and NO2 (0.59 [0.51, 0.67]), while the reduction in O-3 appeared to be less related to changes in cognitive function (OR: 0.97 [0.85, 1.10]). The protective association of PM1 reduction was stronger in males than in females. Decreased in PM2.5 dominate the cognitive function benefit relative to PM1, PM10, NO2. Conclusions: The implementation of the clean air action plan led to a significant reduction in PM1, PM2.5, PM10, and NO2, which could slow the decline of cognitive function, while a reduction in O-3 may not.

Automated summary

The implementation of China's clean air action plan has significantly reduced levels of PM1, PM2.5, PM10, and NO2, which can slow down the decline of cognitive function, while a reduction in O-3 may not have the same effect.