Long-term exposure to fine particulate matter and non-alcoholic fatty liver disease: a prospective cohort study

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease and is associated with a higher risk of all-cause and cause-specific morbidity and mortality.1–3 Animal studies suggest that air pollution may play a role in the development of NAFLD.4 5 However, evidence from human studies is limited.6 Here, we prospectively estimated the association between long-term exposure to fine particulate matter (PM2.5) and risk of NAFLD in 58 026 Taiwan residents who received a standard medical screening programme between 2001 and 2016. We excluded participants with (a) missing values of covariates; (b) excess alcohol intake; (c) liver disease at baseline; (d) NAFLD at baseline and (e) only one medical examination (online supplemental figure S1). The final analytic sample included 35 614 participants for fatty liver index (FLI)-based cohort and 34 741 participants for hepatic steatosis index (HSI)-based cohort. We defined the incident NAFLD as the first occurrence of values of FLI>30 or HSI>36, which have been validated in the Asian population.7 8 We estimated annual PM2.5 levels at participants’ residential addresses using multiple satellite-based aerosol optical depth data combined with a chemical transport model.9 Physical examinations were conducted by trained technicians …