Aims: Nonalcoholic fatty liver disease (NAFLD) is reported to contribute to the development of type 2 diabetes, but it is largely unknown whether such a relationship between NAFLD and incident diabetes relates to the severity of NAFLD or it is independent. We aimed to evaluate the association of the severity of NAFLD with development of type 2 diabetes in a retrospective cohort of Korean subjects.
Methods: This study included 7,849 individuals without diabetes who underwent health check-ups annually for 5 years. Based on the presence or absence of fatty liver on ultrasound and serum alanine aminotransferase (ALT) values at baseline, subjects were classified into controls, an increased ALT group without steatosis, a steatosis group with normal ALT, and a group with presumed nonalcoholic steatohepatitis (NASH) with steatosis and an elevated ALT.
Results: At baseline, there was a significant trend of worsening metabolic variables and index of insulin resistance across the groups from the control group to the increased ALT group, the steatosis group and the NASH group. Over 4 years, the incidence of diabetes was 3.5% in the control group, 4.6% in the increased ALT group, 7.3% in the steatosis group, and 11.8% in the NASH group. The hazard ratio (HR) [(95% confidence interval (CI)] of incident diabetes was increased in the increased ALT group, the steatosis group, and the NASH group in a stepwise fashion. Subjects with NASH had a significantly increased HR of 1.64 (1.272.13), even after multivariable adjustment.
Conclusions: The severity of NAFLD as well as the presence of NAFLD has an independent and additive effect on the development of type 2 diabetes. Thus, the evaluation of severity of NAFLD, especially through the clinical diagnosis of NASH, could be included in incident diabetes prediction algorithms.
Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.
Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.