Prevalence and associated metabolic factors of nonalcoholic fatty liver disease in the general population from 2009 to 2010 in Japan: a multicenter large retrospective study.

Background: The prevalence of nonalcoholic fatty liver disease (NAFLD) has been increasing. This study aimed to assess the recent prevalence of NAFLD and to predict the prevalence of nonalcoholic steatohepatitis (NASH) with liver fibrosis using established scoring systems in the general population.
Methods: A cross-sectional study was conducted among 8352 subjects who received health checkups from 2009 to 2010 in three health centers in Japan. Subjects with an intake over 20 g of alcohol/day or with other chronic liver diseases were excluded. Fatty liver was detected by ultrasonography. The probability of NASH with advanced fibrosis was calculated according to the body mass index, age, ALT, and triglyceride (BAAT) and FIB-4 (based on age, aspartate aminotransferase and alanine aminotransferase levels, and platelet counts) indices.
Results: A total of 5075 subjects were enrolled. The overall prevalence of NAFLD was 29.7%. There was a significant threefold difference in the mean prevalence between males (41.0%) and females (17.7%). This prevalence showed a linear increase with body mass index, triglycerides, and low-density lipoprotein cholesterol regardless of threshold values, even without obesity. The estimated prevalence of NASH according to the BAAT index ≥3 was 2.7%, and according to the FIB-4 index it was 1.9%.
Conclusions: The prevalence of NAFLD has increased in the general population, especially in males. There is a linear relationship between the prevalence of NAFLD and various metabolic parameters, even in nonobese subjects. The prevalence of NASH with advanced fibrosis is estimated to be considerably high in subjects with NAFLD.