Evidence for liver injury in the setting of obstructive sleep apnea

Introduction. Obstructive sleep apnea (OSA) and non-alcoholic fatty liver disease (NAFLD) are both strongly associated with obesity. Whether OSA is an independent risk factor for liver injury is uncertain. Objective. To assess the hypothesis that OSA is associated with liver injury independent of obesity. Materials and methods. We reviewed the histories of 73 consecutive patients referred to a hospital-based sleep lab because of suspected OSA. OSA was determined to be present if the apnea-hypopnea index was > 10. Obesity was defined as a BMI >= 30 kg/m(2). Patients were included for analysis if they had aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels obtained within 60 days of sleep study. Patients with evidence of viral hepatitis, autoimmune-, metabolic- or established alcoholic-liver disease were excluded. Patients who reported alcohol intake equivalent to a dose >= 20 g/day were also excluded. 53 of 73 patients met study criteria. Patients were subdivided for analysis into groups meeting or not meeting OSA and obesity criteria, and having or not having elevated aminotransferase levels. Results. 35/53 patients (66%) had OSA. 31/53 (58%) patients were obese. 15 (28%) and 12 (23%) patients had elevated AST and ALT, respectively. Mean age, gender distribution, mean BMI and percentage with either diabetes or hyperlipidemia were not significantly different in those with or without OSA. Elevated ALT was found in 11/35 (31%) patients with OSA, compared to 1/18 patients without OSA (p = 0.041). Frequency of elevated AST [obese 11/31(35%); non-obese 4/22 (18%)] or ALT [obese 10/31 (32%); non-obese 2/22 (9%)] was not significantly different in the obese and non-obese cohorts. Conclusions. OSA may be a risk factor for liver injury independent of obesity. The prevalence and nature of liver disease in the setting of OSA should be determined with larger, prospective studies. The impact of OSA treatment, if any, on liver injury should be similarly evaluated.