Abstract
BACKGROUND: Visual impairment (VI) poses an increasing global health burden, yet the long-term effects of fine particulate matter (PM(2.5)) constituents on VI remain unclear. This study aimed to evaluate associations between long-term exposure to PM(2.5) and its constituents and the risk of VI. METHODS: We used data from the nationally representative China Health and Retirement Longitudinal Study (CHARLS, 2011–2018) including adults aged ≥ 45 years. Long-term exposure to PM(2.5) and its constituents (SO(4)(2–), NO(3)(–), NH(4)(+), organic matter (OM), and black carbon (BC)) was obtained from the Tracking Air Pollution in China dataset and linked to participants’ residential cities. The 3-year moving average concentration was used as the primary exposure metric to capture cumulative effects, while the 1-year average concentration was applied for sensitivity analysis. VI was defined as self-reported fair or poor vision. Associations were estimated using time-dependent Cox models, with restricted cubic spline (RCS), stratified and interaction analyses to assess nonlinear and subgroup effects. RESULTS: Over 27,443 person-years of follow-up, 3,736 participants developed VI. Per interquartile range (IQR) increase in 3-year moving average concentrations, higher risks of VI were observed for PM(2.5) (HR = 1.09, 95% CI: 1.03–1.15), SO(4)(2–) (HR = 1.13, 95% CI: 1.05–1.22), NO(3)(–) (HR = 1.06, 95% CI: 1.00–1.13), NH(4)(+) (HR = 1.09, 95% CI: 1.02–1.17), OM (HR = 95% CI: 1.15, 1.07–1.24), and BC (HR = 1.24, 95% CI: 1.14–1.34). RCS analysis revealed non-linear associations for PM(2.5), NO(3)(–), NH(4)(+), and OM, whereas SO(4)(2–) and BC showed approximately linear trends. Associations were more pronounced among older adults (> 60 years old), smokers, and those with hypertension. CONCLUSION: Long-term exposure to PM(2.5) and its constituents significantly increases the risk of VI among middle-aged and older adults in China, highlighting the need for targeted environmental health policies. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12889-025-25648-y.