Nonalcoholic Fatty Liver Disease Is Associated With Decreased Lung Function

Chang-Hoon Lee; Seung Ho Choi; Goh Eun Chung; Boram Park; Min-Sun Kwak

Disclosures

Liver International. 2018;38(11):2091-2100. 

In This Article

Abstract and Introduction

Abstract

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.

Introduction

Nonalcoholic fatty liver disease (NAFLD), which has been recognized as the most common chronic liver disease, has a prevalence of 20%–30% in the general population.[1] Although NAFLD usually follows a benign clinical course, when simple steatosis progresses to nonalcoholic steatohepatitis (NASH), 25% of patients may experience progressive liver fibrosis and cirrhosis.[2] NAFLD is regarded as the hepatic manifestation of metabolic syndrome, as it is closely associated with metabolic conditions, including insulin resistance, abdominal obesity, dyslipidemia and type 2 diabetes.[3] An increasing number of studies suggest that NAFLD is associated with cardiovascular disease and chronic kidney disease independently of traditional cardiovascular risk factors.[4,5]

Lung function is traditionally associated with demographic and physical attributes, including ethnicity, age, sex, height and weight.[6,7] In the past decade, studies have reported impaired lung function in several metabolic conditions such as diabetes, insulin resistance and metabolic syndrome.[8–10] Recently, several studies showed that lung function is closely associated with NAFLD.[11–13] Our previous population-based study also showed an inverse association between NAFLD (evaluated by serum testing) and lung function, predominantly in males.[14]

However, all these previous studies used cross-sectional designs. There are no longitudinal studies investigating the impacts of NAFLD on lung function decline, although lung function decline is regarded an important health outcome in the general population[15,16] and among people with chronic respiratory diseases.[17,18] Therefore, the aims of our study were to investigate (i) whether NAFLD as evaluated by ultrasonography is associated with decreased lung function in a large-scale cross-sectional study and (ii) whether NAFLD is associated with accelerated lung function decline in a longitudinal study. We also evaluated whether hepatic fibrosis is associated with lung function decline.

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