Prevalence of non-alcoholic fatty liver disease and its association with impaired glucose metabolism in Japanese adults

Aims To assess the prevalence of non-alcoholic fatty liver disease (NAFLD) and its association with impaired glucose metabolism in Japanese subjects. Methods One thousand, nine hundred and fifty subjects enrolled in a general health examination programme from September 2002 to February 2003 were recruited. NAFLD was diagnosed if a person showed 'fatty liver' on ultrasonography, and his/her alcohol consumption, estimated by questionnaire, was < 40 gram/week. A general linear model was used for the comparison of estimated means of metabolic variables adjusted for age and body mass index (BMI) between subjects with NAFLD and those without fatty liver. Multivariate regression with fasting plasma glucose (FPG) as the dependent variable was performed in 1547 non-diabetic individuals after adjusting for age, gender, BMI and NAFLD. Results NAFLD was found in 566 of the 1950 health-check examinees (29%). Its prevalence increased with increasing FPG levels: 27% in the subgroup with normal fasting glucose, 43% in impaired fasting glucose and 62% in newly diagnosed diabetes. Adjusted means of FPG, HbA(1c), triglyceride, total protein, albumin, AST and ALT were all significantly higher, while adjusted means of HDL cholesterol and AST/ALT ratio were significantly lower in subjects with NAFLD than those without fatty liver. Multivariate regression analysis showed that NAFLD was independently associated with increasing FPG in non-diabetic individuals. Conclusions The prevalence of NAFLD was 29% in apparently healthy middle-aged Japanese adults and NAFLD was independently associated with impaired glucose metabolism.