BACKGROUND & AIMS The association between nonalcoholic fatty liver disease and lung function has not been fully examined. The aim of this study was to clarify the association between nonalcoholic fatty liver disease and lung function in general population by performing cross-sectional and longitudinal analysis.

METHODS Participants without hepatic and respiratory disease who underwent regular health exams including hepatic sonography and spirometry with at least 3 years' follow-up were included. In cross-sectional analysis, the association between nonalcoholic fatty liver disease and lung function at baseline was examined with multiple regression models. The longitudinal analysis was performed by mixed linear regression models with propensity score matching.

RESULTS Of 11 892 eligible participants (mean age, 47.7 years; male, 47.2%), 3815(32.1%) had nonalcoholic fatty liver disease based on sonography. In cross-sectional analysis, the nonalcoholic fatty liver disease group had lower adjusted forced expiratory volume in 1-second (men, 3.52 vs 3.44 L, P < .001; women, 2.62 vs 2.45 L, P < .001) and forced vital capacity (men, 4.33 vs 4.24 L, P < .001; women, 3.11 vs 2.97 L, P < .001) than the control group. In longitudinal analysis, during the mean follow-up period of 6.6 years, there were no significant differences in forced expiratory volume in 1-second or forced vital capacity decline rates between two groups in the propensity score-matched cohorts (n = 4558). However, those with high nonalcoholic fatty liver disease fibrosis score and fibrosis-4 (men, -21.7 vs -27.4 mL/y, P = .001; women, -22.4 vs -27.9 mL/y, P = .016) showed significantly faster decline in forced vital capacity compared to those with low scores.

CONCLUSIONS Nonalcoholic fatty liver disease was associated with decreased lung function at baseline but was not associated with accelerated lung function decline in the propensity score-matched cohort. However, hepatic fibrosis was significantly associated with rapid forced vital capacity decline.