The association of long-term air pollution with a composite neurodegenerative risk score among Chinese elderly: evidence from the CHARLS

Abstract

The relationship between long-term exposure to air pollution and the risk of neurodegenerative diseases has drawn increasing attention. However, the relative effects of various pollutants and the potential role of systemic inflammation remain unclear. This study aims to explore the association between various air pollutants and the comprehensive risk score of neurodegenerative diseases in the middle-aged and elderly population in China, and to examine the effect modification of baseline high-sensitivity C-reactive protein (hs-CRP) and white blood cell count (WBC). The data were sourced from the China Longitudinal Study of Health and Retirement (CHARLS) and the National Earth System Science Data Center. The average concentrations of fine particulate matter (PM2.5), inhalable particulate matter (PM10), nitrogen dioxide (NO2), and ozone (O3 ) from 2012 to 2015 were obtained through processing by the ArcGIS platform. The outcome was the comprehensive risk score and its ternary scale constructed by grip strength, the Central Depression Scale (CES-D-10), the Mini-Mental State Examination (MMSE), and instrumental activities of daily living (IADL) at the follow-up in 2015. A two-stage analysis was adopted: Firstly, multiple linear regression (OLS) was used to analyze the association between pollutants and continuous scores; Then, ordered Logistic regression was applied. After adjusting for the baseline score in 2011, age, gender, education, urban and rural residence, and the number of chronic diseases, the association between pollutants and risk levels was analyzed, and age stratification analysis of pollutants was conducted (30-59 years old, 60-74 years old, ≥75 years old). The effect modification effect was examined by incorporating the interaction term between pollutants and baseline inflammatory markers into the model. OLS regression analysis showed that long-term PM2.5 exposure was significantly associated with an elevated comprehensive neurodegenerative risk score (adjusted β = 0.010, 95% CI: 0.008-0.016), while the associations with PM10, NO2, and O3 were not significant. Ordered Logistic regression analysis showed that, after adjusting for covariates, only PM2.5 was significantly associated with a higher neurodegenerative risk score grade (OR= 1.52, 95% CI: 1.01-2.31), and this association was specific to the 60-74 age group. Baseline hs-CRP and WBC levels had no significant effect modification on the association between pollutants and the comprehensive risk score of neurodegeneration (P > 0.05). In the study population, long-term PM2.5 exposure was associated with an elevated comprehensive neurodegenerative risk score, especially among the elderly aged 60-74. No significant modifying effect of baseline inflammatory levels on this association was found. The research results suggest that air pollution control and targeted intervention for the elderly population have potential public health significance.