Epidemiology of non-alcoholic fatty liver disease in Asia

The growing burden of non-alcoholic fatty liver disease (NAFLD) parallels the increasing prevalence of obesity in Asia. The overall prevalence of NAFLD in Asia is now estimated to be 29.6% and may have surpassed that in Western populations. NAFLD increases with increasing age and is closely associated with metabolic syndrome. Ethnic differences exist in the prevalence of NAFLD, but the underlying factors are unclear. There were initial concerns about lean NAFLD being associated with more severe liver disease and increased mortality, but subsequent studies suggested otherwise. Only some NAFLD patients progress to develop advanced liver fibrosis and cirrhosis, while the liver status remains unchanged in the majority; fibrosis stage is the most important predictor of disease-specific mortality in NAFLD. Surveillance for hepatocellular carcinoma (HCC) remains a challenge due to undiagnosed cirrhosis and the development of HCC in non-cirrhotic NAFLD patients. Diabetes mellitus shares a bidirectional relationship with NAFLD; NAFLD is highly prevalent among patients with diabetes mellitus, and diabetes mellitus is associated with more severe NAFLD. Chronic hepatitis B (CHB) is a major cause of chronic liver disease in Asia; NAFLD and CHB are increasingly observed together because of the increasing prevalence of NAFLD. Despite studies reporting favorable virologic outcome in CHB patients with NAFLD, NAFLD has been found to be independently associated with fibrosis progression and poorer prognosis in CHB patients. Therefore, NAFLD in CHB patients should be given more attention.