Objective To investigate the effect of long-term exposure to PM_2.5 and its chemical components on frailty risk among middle-aged and older adults in China.

Methods A prospective cohort study was conducted using data from the China Health and Retirement Longitudinal Study (CHARLS) collected between 2011 and 2020 and the Tracking Air Pollution (TAP) dataset. The frailty status of the participants was assessed using the frailty index. A time-dependent Cox proportional hazards model was applied to examine the associations between frailty risk and long-term exposure to PM_2.5 and its chemical components, including black carbon, organic matter, sulfate, nitrate, and ammonium.

Results A total of 9603 participants were included in the analysis. After adjusting for potential confounders, each interquartile range increase in the average PM_2.5 concentration during the preceding year was associated with a 10.0% higher risk of frailty (hazard ratio HR = 1.100, 95% CI: 1.015-1.193). For individual chemical components, each interquartile range increase in the one-year average concentrations of organic matter, black carbon, ammonium, sulfate, and nitrate, the participants were exposed to was associated with a 14.2% (HR = 1.142, 95% CI: 1.055-1.236), 13.1% (HR = 1.131, 95% CI: 1.041-1.229), 9.8% (HR = 1.098, 95% CI: 1.010-1.194), 8.8% (HR = 1.088, 95% CI: 0.996-1.187), and 8.1% (HR = 1.081, 95% CI: 0.996-1.172) higher risk of frailty, respectively.

Conclusion Long-term exposures to PM_2.5 and its chemical components, particularly black carbon, organic matter, and ammonium, were associated with a higher risk of frailty among middle-aged and older adults in China. Priority should be given to strengthening emission control of black carbon and organic aerosols to mitigate the public health burden of air pollution in the context of an aging society.