The impact of severe obstructive sleep apnea and obesity on nonalcoholic fatty liver disease

Background: Obstructive sleep apnea (OSA) and its associated intermittent hypoxia have been implicated in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). Aim: to evaluate the relationship between severe OSA and NAFLD and to correlate features of NAFLD with the clinical course of OSA. Material and Methods: We enrolled 85 consecutive patients (62 men and 23 women, mean age 56.2±11.3 yrs) with severe OSA (AHIu003e30/h) confirmed by polysomnography (mean AHI- 59.4±19.7/h). Alcohol abuse was a major exclusion criterion. All subjects underwent blood laboratory testing. Severity of liver steatosis was assessed by ultrasound (US) (GE, Vivid 9) using tissue intensity analysis software (GE, Echopac, Q analysis) and based on the difference in echogenicity (DIFF) between liver parenchyma and the cortex of the right kidney. The echogenicity difference of u003e5 dB was applied as diagnostic criterion for fatty liver. Data from patients with AHI 30-60/h and AHI u003e60/h were compared. Results: overall, US criteria for fatty liver were found in 57 (67%) patients. The severity of liver steatosis showed a weak but significant correlation with BMI (r=0.23, p0.046) and AHI (r=0.31, p=0.005). We did not find any correlations between the severity of liver steatosis and age, oxygen desaturation index (ODI), serum cholesterol and triglycerides. There were no differences in the severity of liver steatosis in patients with AHI 30-60/h (45 subjects) and those with AHI u003e 60/h (40 subjects) – 49.5 vs 49.8 units, respectively, pu003e0.05. Conclusions: Our study showed that BMI and AHI are associated with to non-alcoholic fatty liver in subjects with severe OSA.