Association of long-term ambient fine particulate matter (PM2.5) and incident non-alcoholic fatty liver disease in Chinese adults

Air pollution is increasingly recognized as an important environmental risk factor for non-alcoholic fatty liver disease (NAFLD). However, epidemiologic evidence on long-term exposure to high air pollution concentrations with incident NAFLD is still very limited. Here, we constructed a population-based dynamic cohort involving 17,106 subjects who were enrolled between 2005 and 2013 and subsequently followed until 2017, combined with a high-resolution ambient fine particulate matter ≤2.5 μm (PM2.5) dataset, to investigate the association of long-term PM2.5 exposure (cumulative annual average levels ranged from 36.67 to 111.16 μg/m3) with NAFLD incidence (N = 4,640). We estimated the adjusted hazard ratio (HR) for incident NAFLD among those exposed to the highest quartile of PM2.5 was 2.04 [95% confidence interval (CI), 1.80-2.30] compared with individuals exposed to the lowest quartile of PM2.5. The dose-response relationships for PM2.5 are non-linear for NAFLD across the exposure distribution. Further stratified analyses revealed that lean (<23 kg/m2), younger (<40-year-old), and women individuals appeared more vulnerable to the harmful effects of PM2.5 exposure. Our study suggests a greater long-term high ambient PM2.5 exposure is associated with an increased risk of NAFLD in Chinese adults, particularly in specific groups, including lean, women, and younger people.