Association between obstructive sleep apnea and nonalcoholic fatty liver disease

Abstract

Objectives: We aimed to study the association between obstructive sleep apnea (OSA) and nonalcoholic fatty liver disease / steatohepatitis (NAFLD/NASH). Methods: 41 OSA cases, diagnosed by overnight polysomnography with apnea/hypopnea index (AHI) >5 events/hour, and 9 COPD cases as control group were studied. A blood sample was taken for fasting blood glucose, liver enzymes, and arterial blood gases just after awake. Abdominal ultrasound (US) was performed to all patients and ultrasonographic fatty score was calculated ranging 2-8 based on hepatic echogenicity, visualization of the hepatic vessels and diaphragm, posterior attenuation of the ultrasound beam, visualization of gall bladder wall and areas of focal sparing. BARD score was calculated as BMI ≥28=1, AST/ALT ratio ≥ 0.8=2, diabetes=1. Results: 63.4% of OSA cases were males vs. 100% of controls with age of 51.9±9.9 vs. 60.7±9.2 years respectively. BMI was 41.7±8.9 kg/m2 for cases vs. 29.9±2.5 kg/m2 for controls (p<0.001). AHI was 45.5±29.6 events/hour with average O2 saturation of 87.6±7.9%. According to US fatty score, 41.5% had NAFLD and 43.9% had NASH among OSA cases vs. 11% of the controls had NAFLD (score 3.2±1.6 vs. 0.3±0.7 respectively; p<0.001). US fatty score correlated positively with BMI (r=0.359, p=0.023). BARD score was not significantly different between both groups (2.76±0.97 vs. 2.56±0.88 respectively; p=0.372). However, PaO2 among OSA cases and BARD score were positively correlated (r=0.303, p=0.054). There were no significant correlations between AHI and BARD or US fatty scores (p>0.05). Conclusions: Obesity associated with OSA is important cause of NAFLD/NASH but associated hypoxemia may be also implicated.