Obstructive sleep apnea (OSA) and nonalcoholic fatty liver disease (NAFLD) are frequently encountered in patients with metabolic syndrome (MS). Several data suggest that OSA per se could be a risk factor of liver injury. Most previous studies evaluating the association between OSA severity and the severity of NAFLD used indirect markers of NAFLD including liver imaging or liver injury blood markers or have been performed in morbidly obese patients undergoing intraoperative needle liver biopsy during bariatric surgery.