Prevalence and health checkup-based detection of metabolic dysfunction-associated steatotic liver disease in Japanese young adults.

We aimed to elucidate the prevalence of steatotic liver disease (SLD) in Japanese young adults and to identify health checkup-based markers for metabolic dysfunction-associated steatotic liver disease (MASLD). We recruited participants (18–29 years) attending a health checkup. Abdominal ultrasonography and health checkup data were used to diagnose and classify SLD. The diagnostic ability of serum alanine aminotransferase (ALT), fatty liver index (FLI), and hepatic steatosis index (HSI) were evaluated using receiver operating characteristic curve analysis. Among the 1632 participants in 2023, 1004 (62%) were male, and SLD was observed in 271 (17%). In the SLD subclass, 143 (9%), 1 (< 1%), 0 (0%), and 127 (8%) were diagnosed with MASLD, MASLD with moderate alcohol intake, alcohol-associated/related liver disease, and cryptogenic SLD, respectively. The area under the curve of ALT, FLI, and HSI to identify MASLD were 0.76, 0.85, and 0.84, respectively. The cutoff value of ALT to rule in (specificity 0.90) MASLD was 31 IU/L. Similar results were observed in 1743 participants in 2024. In conclusion, the prevalence of SLD and MASLD in Japanese young adults was 17% and 9%, respectively. ALT > 30 IU/L was identified as a reasonable cutoff value to identify MASLD in Japanese young adults.