Prevalence trends of non-alcoholic fatty liver disease among young men in Korea: A Korean military popula-tion-based cross-sectional study

Background/Aims: Non-alcoholic fatty liver disease (NAFLD) has become a major concern in Korea since its emergence as a dominant cause of chronic liver disease. However, no study has explored its prevalence in adults under 30 years of age. Therefore, we performed a cross-sectional study to investigate the prevalence of NAFLD in Korean men in their early 20s. Methods: We collected data of 596,359 Korean soldiers who participated in a health examination between January 2015 and July 2021. A total of 571,872 individuals were analyzed after excluding those with missing data and hepatitis B antigen positivity. Hepatic steatosis was determined using the hepatic steatosis index (HSI). Participants with HSI >36 were considered to have NAFLD. Results: All participants were men, and the mean age was 20.9±1.3 years. Of the 571,872 participants screened, 77,020 (13.47%) were classified as having NAFLD. The prevalence of NAFLD consistently increased from 2015 to 2021 (10.66% vs. 16.44%, P<0.001). Increases from 2015 to 2021 were also noted in the prevalence of hypercholesterolemia, hyperglycemia, and hypertension (P<0.001 for all). The mean body mass index also increased from 23.3±3.0 kg/m² to 23.9±3.1 kg/m² between 2015 and 2021 (P<0.001). Conclusions: The prevalence of NAFLD and of other metabolic dysfunctions in Korean men in their early 20s increased from 2015 to 2021.