Long-term exposure to ambient air pollution and the incidence of nonalcoholic fatty liver disease: a cohort study.

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) affects approximately one-third of adults and may progress to advanced fibrosis and hepatocellular carcinoma. Epidemiologic studies linking air pollution to NAFLD incidence remain limited. This study examined associations between long-term exposure to ambient air pollution and NAFLD incidence.

METHODS

The study included 62 660 adults in Taiwan undergoing health examinations from 1996 to 2016. NAFLD was diagnosed through liver ultrasonography; individual characteristics and medical history were obtained from questionnaires. Residential township data estimated exposure to fine particulate matter (PM2.5), nitrogen dioxide (NO2), and carbon monoxide (CO). Time-dependent Cox regression was conducted to assess associations between air pollution and NAFLD incidence.

RESULTS

The overall NAFLD incidence was 53.0 cases per 1000 person-years. Adjusted models showed positive associations between air pollutants and NAFLD. Compared with low exposure to both PM2.5 and NO2, the adjusted hazard ratio (HR) [95% confidence interval (CI)] for high exposure to both was 1.25 (1.19-1.31). Similarly, compared with low exposure to both PM2.5 and CO, the adjusted HR (95% CI) was 1.12 (1.07-1.17) for low PM2.5 and high CO, and 1.28 (1.22-1.33) for high exposure to both.

CONCLUSION

Long-term exposure to PM2.5 and traffic-related air pollutants, including NO2 and CO, may increase the risk of developing NAFLD.