Obstructive Sleep Apnea Is Associated with Fatty Liver and Abnormal Liver Enzymes: a Meta-analysis

Obstructive sleep apnea (OSA) is associated with the cluster of clinical conditions that comprise the metabolic syndrome, including nonalcoholic fatty liver disease (NAFLD). Our primary purpose was to estimate the effect of OSA on serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Our secondary purpose was to investigate the potential influence of OSA on histological severity of NAFLD to explore whether chronic intermittent hypoxia is associated with inflammation and fibrosis. Our literature search identified 11 studies, from which we extracted information about numbers of control subjects and OSA patients, and ALT, AST, and NAFLD. From a total of 668 OSA patients and 404 controls, we found that the standardized difference in mean values of ALT and AST levels in patients with OSA was significantly different from that in the controls. Meta-regression showed that the association was independent of body mass index and type 2 diabetes. Fatty liver was associated with OSA in five studies with 400 subjects. OSA was significantly associated with liver fibrosis in 208 subjects, but not with lobular inflammation. Routine assessment of liver enzymes and liver damage should be implemented in OSA patients because they have an increase of 13.3 % of ALT and 4.4 % of AST levels, and a 2.6-fold higher risk of liver fibrosis when they have NAFLD, which is 2.6 times more frequent in OSA patients.