Effect of particulate matter on cognitive function among middle-aged and older adults in China: An instrumental variable approach

Emerging studies have suggested the association of ambient air pollution with worse cognitive function; however, causal evidence remains scarce. We aimed to estimate the effect of particulate matter (PM) exposure on overall and domain-specific cognitive function. A total of 14,205 participants aged 45 years and above were drawn from the 2015 wave of the China Health and Retirement Longitudinal Study (CHARLS). Cognitive function was assessed using a standardized questionnaire consisting of two domains: episodic memory and mental status. Participants’ exposure to city-level PM (PM1, PM2.5, and PM10) was evaluated using satellite-based spatiotemporal models. To avoid potential endogenous biases, an instrumental variable method with two-stage least squares estimation was employed to examine the effect of air pollution on overall and domain-specific cognitive function. Stratified analysis was further performed based on sociodemographic characteristics. We found PM exposure exertedsignificant adverse effects on overall and domain-specific cognitive function, with mental status being more adversely affected as compared to episodic memory. The effect of PM exposure was more pronounced with smaller particle sizes, with PM1 exhibiting the largest effect size. Moreover, participants with lower education attainment were more adversely affected by PM exposure. Our findings add additional evidence of the potential causal role of PM exposure in worsening overall and domain-specific cognitive function. Efforts to further reduce PM are needed to protect the cognitive health of the aging Chinese population.