P-0110 - PM2.5 air pollution exposure and nonalcoholic fatty liver disease in the United States

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Background: Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease. Upwards of 30% of NAFLD cases occur among people who are non-obese (i.e., “lean NAFLD”) and up to 52% among people without diabetes. Particulate matter air pollution <2.5 µm in diameter (PM2.5) is a ubiquitous exposure primarily produced from fossil fuel combustion. Once inhaled, PM2.5 particles can enter the bloodstream and induce lipid accumulation, oxidative damage, inflammation, and fibrosis in the liver of mice. Previous epidemiologic research has been limited by small study areas with little exposure variability. Our aim was to conduct the first nationwide study to examine the association between ambient PM2.5 exposure and NAFLD.
Methods: We conducted cross-sectional analyses of hospitalizations between 2001 and 2011 from the Nationwide Inpatient Sample (NIS), the largest nationally representative all-payer inpatient care administrative database in the United States. Average annual PM2.5 exposure was estimated using NIS ZIP Codes linked with the Environmental Protection Agency Downscaler Model, which incorporates data from atmospheric modeling and point air pollution measurements. NAFLD hospitalizations were identified using International Classification of Diseases discharge diagnosis codes excluding unrelated liver diseases. Multilevel logistic regression accounting for the complex survey design with a random effect for hospital was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs) adjusted for age, sex, race/ethnicity, year, obesity, diabetes, smoking, hypertension, dyslipidemia, obstructive sleep apnea, and individual- and area-level socioeconomic status.
Results: The prevalence of NAFLD hospitalizations was 3.4% from 2001-2011 (unweighted 122,913 cases/36,065,973 hospitalizations). Preliminary results show that higher ambient PM2.5 exposure was associated with increased odds of NAFLD hospitalizations (adjusted OR 1.17, 95% CI 1.03-1.32 per 10 µg/m3 increase).
Conclusions: PM2.5 may be a novel risk factor for NAFLD. Future analyses will examine potential effect modification by age, race/ethnicity, sex, and geography.