Nonalcoholic Fatty Liver Disease Is a Risk Factor for Type 2 Diabetes in Middle-Aged Japanese Men

Abstract

OBJECTIVE—To determine the association between nonalcoholic fatty liver disease and the risk for development of diabetes. RESEARCH DESIGN AND METHODS—We conducted an observational cohort study in male workers ≥40 years old in a Japanese company from 1997 to 2005. We excluded workers with alcohol intake ≥20 g/day and those with impaired glucose tolerance by a 75-g oral glucose tolerance test. The remaining 3,189 workers were classified into fatty liver (FL) and non-FL group based on the findings of abdominal ultrasonography. Both groups were followed for the development of diabetes. Hazard ratio (HR) was determined in Cox proportional hazard analysis. A nested case-control study was conducted to determine the odds ratio (OR). RESULTS—The average age of participants was 48.0 years at the entry, and the average follow-up period was 4.0 years. The incidence of diabetes in the FL group was 2,073 per 100,000 person-years (65 cases), whereas 452 per 100,000 person-years (44 cases) in the non-FL group. The age- and BMI-adjusted HR of diabetes associated with FL was 5.5 (95% CI 3.6–8.5, P < 0.001). In the nested case-control analysis, the OR adjusted for age and BMI was 4.6 (3.0–6.9, P < 0.001). CONCLUSIONS—Nonalcoholic fatty liver disease significantly increases the risk of diabetes in middle-aged Japanese men.