Obstructive Sleep Apnea and Non-alcoholic Fatty Liver Disease in Obese Patients Undergoing Bariatric Surgery

BACKGROUND: Morbid obesity is associated with multiple comorbidities including obstructive sleep apnea (OSA) and non-alcoholic fatty liver disease (NAFLD). It has been suggested that OSA may contribute to NAFLD pathogenesis due to intermittent nocturnal hypoxia. PURPOSE: The objective of this study was to assess the apnea-hypopnea index (AHI) and lower minimum oxygen saturation, markers of OSA, in patients undergoing bariatric surgery (BSx) with perioperative liver biopsy to detect NAFLD. METHODS: This was a single center cross-sectional study of 61 patients undergoing BSx who consented to have a perioperative wedged liver biopsy. Biochemical, clinical, anthropometric variables, and a sleep study test were performed prior to BSx. RESULTS: NAFLD was diagnosed in 49 (80.3%) patients; 12 had normal liver (NL). Those with NAFLD had significantly higher (p < 0.05) AST (42.6 vs 18.1 U/L) and ALT (35.0 vs 22.1 U/L) but similar clinical, anthropometric, and metabolic parameters to NL. There was a higher AHI (32.03 vs 14.35) and significantly lower minimum oxygen saturation (SaO2) (78.87 vs 85.63) in NAFLD compared with NL (p < 0.05). When assessing associations between OSA parameters and liver histology in NAFLD, AHI correlated significantly with lobular inflammation (p < 0.05). In a multivariate analysis, BMI was significantly correlated with lobular inflammation with mean SaO2 nearing significance. CONCLUSIONS: These results indicate that in a homogeneous bariatric population sample with similar characteristics, those with NAFLD had higher AHI and lower minimum SaO2 compared with NL. AHI correlated with liver inflammation suggesting a potential role for intermittent nocturnal hypoxia in the pathogenesis and progression of NAFLD.