Changes in Fatty Liver Disease and Incident Diabetes Mellitus in Young Korean Adults.

Introduction: This study sought to assess the association between the changes in nonalcoholic fatty liver disease (NAFLD) and risk of type 2 diabetes in young individuals with prediabetes.

Methods: Data from the Korean National Health Insurance System database were collected from 2009 to 2019 and analyzed in 2022. A total of 446,813 young adults aged 20-39 years with prediabetes who underwent two National Health Screening examinations from 2009 to 2012 were followed up. NAFLD was defined as a fatty liver index≥60 without liver disease or history of alcohol abuse. Multivariable Cox proportional hazards regression was used to calculate the HR and CIs for type 2 diabetes according to NAFLD changes.

Results: During a median follow-up of 8.3 years, 26,464 (5.9%) young individuals developed type 2 diabetes. Multivariable adjusted HR of type 2 diabetes according to the NAFLD change was 5.38 (95% CI 5.08-5.70) in individuals with persistent NAFLD when compared to those who never had NAFLD. Even in individuals who were consistently nonobese, resolved NAFLD, new NAFLD, and persistent NAFLD were associated with>3-fold increased risk of type 2 diabetes compared to nonobese individuals without NAFLD. The risk of type 2 diabetes also increased in obese individuals without NAFLD by 2-fold when compared to nonobese individuals without NAFLD.

Conclusions: NAFLD that either existed persistently or ever existed plays a critical role in the development of type 2 diabetes in young adults with or without obesity. Nonobese individuals with NAFLD warrant special attention.