Particulate matter, socioeconomic status, and cognitive function among older adults in China

Both air pollution and low socioeconomic status (SES) are associated with worse cognitive function. The extent to which low SES may compound the adverse effect of air pollution on cognitive function remains unclear.

7,087 older adults aged 65 and above were included from the Chinese Longitudinal Healthy Longevity Survey (CLHLS) and followed up in 4 waves during 2008-2018. Cognitive function was measured repeatedly at each wave using the modified Chinese Mini-Mental State Examination (MMSE). Concentrations of particulate matter (PM₁, PM_2.5, and PM₁₀) were evaluated using satellite-based spatiotemporal models. SES was measured based on five components and categorized into three levels (low, middle, and high). Generalized estimating equation models were used to estimate the association of PM and SES with cognitive function. Stratified analyses and effect modification by SES levels were further conducted.

Each 10 µg/m³ increase in PM₁, PM_2.5, and PM₁₀ was associated with a 0.43 (95 % CI: -0.58, -0.27), 0.29 (95% CI: -0.37, -0.20), and 0.17 (95 % CI: -0.22, -0.13) unit decrease in MMSE scores, respectively. Lower SES was associated with worse cognitive function. Significant effect modifications were observed by SES, with the corresponding association of PM exposure being more pronounced among participants with a lower SES (p-interaction = 0.006, 0.001, and 0.006 for PM₁, PM_2.5, and PM₁₀, respectively).

SES is an important effect modifier, and lower SES may compound the detrimental effect of PM on cognitive health. This finding may have implications for identifying vulnerable populations and targeted interventions against air pollution.