Impact of continuous positive airway pressure therapy for nonalcoholic fatty liver disease in patients with obstructive sleep apnea

BACKGROUND Obstructive sleep apnea(OSA)has been suggested as an independent risk factor for nonalcoholic fatty liver disease(NAFLD),and continuous positive airway pressure(CPAP)is the first-line therapy for OSA.AIM To clarify the efficacy of effective CPAP therapy on NAFLD of OSA patients by serum markers and transient elastography(TE)using FibroScan®(Echosens,Paris,France).METHODS We prospectively enrolled 123 consecutive patients with OSA who met the indications for CPAP.Liver fibrosis and steatosis were assessed using TE.Before and after 6 mo of CPAP therapy,serum markers and TE were assessed for all patients.The mean usage rate of CPAP therapy for 6 mo was arbitrarily calculated in each patient and expressed as“mean compliance index”(m-CI).RESULTS In 50 OSA patients with NAFLD,both aspartate aminotransferase(AST)and alanine aminotransferase(ALT)levels were significantly decreased after 6 mo of CPAP therapy.Univariate analysis showed that decreased body weight(BW),decreased body mass index(BMI),decreased AST level,decreased hemoglobin A1c,and high m-CI were significantly related with improved ALT level.In multivariate regression model adjusted for quantities of BW change during 6 mo of CPAP therapy,high m-CI tended to improve ALT level(P=0.051).All 17 OSA patients with NAFLD,high m-CI and no BMI changes showed significant improvements in AST and ALT levels.Meanwhile,no significant changes in TE data or serum fibrosis markers were seen.CONCLUSION Some NAFLD could be associated with chronic intermittent hypoxia due to OSA independent of BW changes.In those cases,adequate reoxygenation from effective CPAP therapy may improve NAFLD.