Association between air pollution and risk of non-alcoholic fatty liver disease: an updated meta-analysis

Objective: Air pollution is a major environmental risk to human health, with increasing evidence linking it to non-alcoholic fatty liver disease (NAFLD). However, findings remain inconsistent. This meta-analysis aimed to assess the relationship between air pollutants and the risk of NAFLD. Methods PubMed, Embase, and Web of Science were systematically searched for studies published up to March 20, 2025. A random effects model was used to estimate combined odds ratios (ORs) and 95% confidence intervals (95% CIs). Subgroup analysis, sensitivity analysis, funnel plots, and Egger's test were conducted. Results A total of 12 studies, including 49,549,903 participants (published between 2022 and 2024), were analyzed. For each 10 μg/m3 increase in pollutants, the ORs were 1.22 (1.16–1.29) for particulate matter with aerodynamic diameter ≤ 2.5 μm (PM 2.5 ), 1.15 (0.95–1.40) for particulate matter between 2.5 and 10 μm in aerodynamic diameter (PM 2.5 − 10 ), and 1.07 (1.01–1.13) for particulate matter with aerodynamic diameter ≤ 10 μm (PM 10 ). For gaseous pollutants, the ORs were 1.45 (0.92–2.28) for sulfur dioxide (SO 2 ) and 1.10 (1.06–1.14) for nitrogen dioxide (NO 2 ). No notable connection emerged between ozone (O 3 ) or carbon monoxide (CO) and NAFLD. Subgroup analysis revealed stronger associations for PM 2.5 , PM 10 , and NO 2 with NAFLD in developed countries, Europe, and cohort studies, compared to developing countries, Asia, and cross-sectional studies. Conclusion This analysis supports a positive relationship between air pollution and NAFLD risk. Geographic region and economic development appear to moderate this association. Systematic review registration https://www.crd.york.ac.uk/PROSPERO/view/CRD42024594146 , Identifier: CRD42024594146.