Association between nocturnal hypoxia and liver injury in the setting of nonalcoholic fatty liver disease

Obstructive sleep apnea (OSA) is suggested as a potential risk factor of nonalcoholic fatty liver disease (NAFLD). However, the underlying mechanism is still far from clear. The aim of this observational study was to investigate the influence of OSA-related hypoxia on severity of liver injury in patients with NAFLD. Consecutive patients with ultrasound-diagnosed NAFLD who underwent standard polysomnography were enrolled. Fasting blood samples were obtained from all patients for biological profile measurements, and demographic data were collected. Subjects were divided into control, moderate, and severe groups. A total of 85 subjects with 73 males and 12 females were included (mean age, 44.67 +/- 1.28 years; mean body mass index, 27.28 +/- 0.33 kg/m(2)). Alanine aminotransferase (ALT), aspartate aminotransferase (AST), ALT/AST, gamma glutamyltransferase, total cholesterol, low density lipoprotein-cholesterol, fasting glucose, and high-sensitivity C-reactive protein significantly increased with the aggravation of OSA. In multivariate analysis, oxygen desaturation index was the major contributing factor for elevated ALT (beta = 0.435, p = 0.000), average O-2 saturation was the major independent predictor of elevated AST (beta = -0.269, p = 0.020). OSA-related hypoxia was independently associated with the biochemical evidence of liver injury in the presence of NAFLD.