Association between obstructive sleep apnea and non-alcoholic fatty liver disease: a systematic review and meta-analysis.

The relationship between obstructive sleep apnea (OSA) and non-alcoholic fatty liver disease (NAFLD) has been an issue of great concern. The primary purpose of this study was to determine the influence of OSA on the levels of liver enzymes including alanine transaminase (ALT) and aspartate transaminase (AST). The secondary purpose was to estimate the effect of OSA on the histological lesions of NAFLD, such as steatosis, lobular inflammation, ballooning degeneration, fibrosis, as well as NAFLD activity score (NAS). A systematic literature review using PubMed, Cochrane Library, Embase, and Ovid technologies from January 2007 to April 2017 was performed, and 9 studies (2272 participants) that met the selection criteria were evaluated. The present study demonstrated that OSA was related to ALT levels, but no significant correlation was found with AST levels. The subgroup analysis showed that the severity of OSA was associated with ALT levels, not with AST levels. The meta-regression analysis showed that age, sex, homeostasis model assessment, diabetes mellitus, body mass index, and waist circumference did not have a significant effect on the levels of ALT and AST. OSA was also found to be significantly correlated with steatosis, lobular inflammation, ballooning degeneration, and fibrosis, but was not correlated with NAS. OSA was independently related to the development and progression of NAFLD in terms of liver enzyme level and histological alterations. Future studies should investigate the possible relevant mechanisms, thereby guiding the exploration of potential therapeutic implications to prevent the progression of disease.