Association between exposure to air pollutants and NAFLD/MAFLD: a meta-analysis

Non-alcoholic fatty liver disease (NAFLD) has become the most prevalent chronic liver disease globally, imposing a significant burden on public health systems. But the link between air pollutants and NAFLD is still unclear, which highlights the need for a systematic meta-analysis to integrate existing evidence.

This study aims to systematically evaluate and quantify the association between exposure to major air pollutants and the risk of NAFLD through a meta-analysis of existing literature.

A thorough search was conducted across Embase, Web of Science, PubMed, and Cochrane Library until February 4, 2025. Pooled risk ratios (RRs) and 95% confidence intervals (95% CI) for NAFLD incidence were calculated with Stata 16.0. Quality assessment was conducted via the NOS scale for cohort studies and the AHQR scale for cross-sectional studies.

Our review included 10 studies. The results manifested that high concentrations of PM2.5 (RR = 1.24, 95% CI: 1.18-1.44), PM10 (RR = 1.24, 95% CI: 1.13-1.36), NO₂ (RR = 1.22, 95% CI: 1.09-1.37) and NOx (RR = 1.24, 95% CI: 1.14-1.36) notably increased NAFLD risk. Each unit increase in PM1 (RR = 1.15, 95% CI: 1.13-1.17), PM2.5 (RR = 1.15, 95% CI: 1.09-1.21), PM10 (RR = 1.10, 95% CI: 1.08-1.11), NO₂ (RR = 1.13, 95% CI: 1.08-1.19) and NOx (RR = 1.10, 95% CI: 1.07-1.14) was also linked with increased NAFLD risk.

The findings suggest plausible associations between exposure to various air pollutants and elevated NAFLD risk. However, high heterogeneity, limited studies, and methodological variability necessitate cautious interpretation and more rigorous research to confirm causality before guiding public health interventions.

Understanding the impact of air pollution on NAFLD is critical for developing targeted public health policies and prevention strategies, particularly in urbanized regions with high pollution levels.