Comparison of prevalence of fatty liver disease according to the different nomenclatures of NAFLD, MAFLD, and MASLD in a large Iranian Population-based study

The terminology and diagnostic criteria for fatty liver disease have undergone recent evolution, from non-alcoholic fatty liver disease (NAFLD) to metabolic dysfunction-associated fatty liver disease (MAFLD), and more recently to metabolic dysfunction-associated steatotic liver disease (MASLD). We aimed to compare the estimated prevalence of FLD with that of NAFLD, MAFLD, and MASLD using different definitions. Data were analyzed from 10,520 participants in the first phase of the Guilan Persian Cohort Study, part of the nationwide PERSIAN Cohort. Participants were classified based on NAFLD, MAFLD, and MASLD. Of 10,520 participants, 5,025 (47.8%) had a fatty liver index (FLI) ≥ 60 and were diagnosed with SLD. The prevalence of MASLD, MAFLD, and NAFLD was 33.7%, 47.6%, and 33.7%, respectively, while 4.5% (n = 471) were classified as metabolic dysfunction-associated alcohol-related liver disease (MetALD). Among those with NAFLD, 99.7% also met MAFLD criteria, and all met MASLD criteria. MAFLD was associated with the highest adjusted odds of elevated FIB-4 (OR: 1.27; 95% CI: 1.24-1.30) and hepatic steatosis index (OR: 2.01; 95% CI: 1.82-2.21). NAFLD and MASLD had a similar, lower prevalence compared to MAFLD. MetALD was not included under MASLD but was encompassed by MAFLD.