The association of non-alcoholic fatty liver disease with lung function: A survey design analysis using propensity score

Abstract

Background and objective: Although both non-alcoholic fatty liver disease (NAFLD) and lung function are known to be associated with metabolic syndromes, few studies have evaluated the relationship between NAFLD and lung function. Our population-based study was conducted to investigate whether NAFLD, diagnosed by elevation of liver enzymes without other chronic liver disease or heavy alcohol drinking, is associated with lung function. Methods: A survey design analysis was performed using national representative data of health and nutritional status of civilians in Korea (Korean National Health and Nutrition Examination Survey, KNHANES) between 2010 and 2012. The criteria for NAFLD diagnosis was elevated serum alanine aminotransferase (ALT) without other chronic liver disease or heavy alcohol drinking. Covariate-adjusted linear regression analyses and post-stratification adjustments to the survey weights based on the propensity scores (PS) were conducted to evaluate the association of NAFLD and lung function, including the forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC). Results: A total of 7417 subjects were included in this analysis. NAFLD was significantly associated with a lower FVC among males as determined by both the covariate-adjusted linear regression analysis (P < 0.01 in all multivariable models) and PS analysis (P = 0.007). In the PS analysis, NAFLD was significantly associated with lower FEV1 (P = 0.044) among males. Among females, NAFLD was associated with a lower FVC according to the linear regression analysis; this finding was not verified with the PS analysis. Conclusion: NAFLD was significantly associated with lower lung function and this relationship was more prominent among males.