Long-term particulate matter exposure accelerates cognitive decline and increases incident mild cognitive impairment...

Inhalable particulate matter (PM) has been linked to cognitive decline, but evidence on size-specific associations between PM and cognitive function and mild cognitive impairment (MCI) in middle-aged and older adults remains limited.

We analysed 5251 participants aged ≥ 45 years without MCI at baseline from the China Health and Retirement Longitudinal Study (CHARLS, 2011-2015). Annual concentrations of PM₁, PM₂.₅ and PM₁₀ (2-year moving averages) were estimated at 1-km resolution and assigned according to participants' residential city. Cognitive function was repeatedly assessed using standardized tests of episodic memory and mental intactness, from which global and domain-specific Z-scores were derived. MCI was defined using age- and education-specific norms. Quantile g-computation estimated baseline mixed PM effects, linear mixed-effects models evaluated longitudinal cognitive change, and time-varying Cox models assessed incident MCI.

Higher baseline mixed exposure to inhalable PM was associated with lower global cognition (per quartile increase in the joint PM mixture: -0.092 SD; 95% CI -0.174 to -0.011). Over follow-up, higher PM₁, PM₂.₅ and PM₁₀ levels (per 10 μg/m³ increase) were associated with modest but statistically significant declines in global cognitive Z-scores, with heterogeneous patterns across cognitive domains. Overall, 1469 participants (27.98%) developed MCI. Long-term exposure to PM₂.₅ and PM₁₀ increased the risk of MCI (HR 1.09; 95% CI 1.005-1.172 and HR 1.16; 95% CI 1.043-1.288 per 10 μg/m³, respectively), whereas PM₁ showed a non-significant positive association.

Long-term exposure to inhalable PM, particularly PM₂.₅ and PM₁₀, was associated with poorer cognitive performance, accelerated cognitive decline, and a higher risk of incident MCI among middle-aged and older adults.