The effect of air pollution on chronic liver disease and the modifying effect of physical activity: a nationwide study from CHARLS.

BACKGROUND: The relationship between ambient air pollution and chronic liver disease (CLD), and whether physical activity (PA) modifies this association, remains unclear. MATERIALS AND METHODS: We analyzed 17,708 middle-aged and older adults from the 2013 China Health and Retirement Longitudinal Study (CHARLS). Individual-level exposures to CO, O3, and NO2 were estimated from the China High Concentration Air Pollutants (CHAP) dataset (0.1°resolution). CLD status was assessed by structured questionnaire. PA was measured using the International Physical Activity Questionnaire (IPAQ) and categorized as light (LPA), moderate (MPA), or vigorous (VPA). Multivariable logistic regression models adjusted for demographic and health covariates were used to estimate odds ratios (ORs) for CLD; effect modification by PA was tested via interaction terms and stratified analyses. RESULTS: In fully adjusted models, higher pollutant levels were associated with increased CLD risk: CO (OR 1.13, 95% CI 1.04-1.19, p = 0.025), O3 (OR 1.15, 95% CI 1.08-1.32, p = 0.014), and NO₂ (OR 1.18, 95% CI 1.09-1.47, p = 0.032). Stratified analyses showed attenuation of pollutant-CLD associations with increasing PA. For CO: LPA 1.15 (0.97-1.46), MPA 0.89 (0.78-1.02), VPA 0.81 (0.61-1.21). For O3: LPA 1.14 (0.93-1.36), MPA 1.09 (0.98-1.21), VPA 0.99 (0.68-1.14). For NO2: LPA 1.05 (0.89-1.21), MPA 0.91 (0.59-1.17), VPA 0.85 (0.61-0.98). Interaction tests were significant for CO (p = 0.021), O3 (p = 0.023), and NO2 (p = 0.028). CONCLUSIONS: Ambient CO, O3, and NO2 are associated with higher CLD risk, and higher PA levels appear to mitigate these associations. Promoting appropriate PA may help reduce pollution-related liver disease burden.