Impact of the New Definition of Metabolic Associated Fatty Liver Disease on the Epidemiology of the Disease

BACKGROUND & AIMS: Recently, a group of hepatologists proposed to rename non-alcoholic fatty liver disease (NAFLD) as metabolic associated fatty liver disease (MAFLD) with modified diagnostic criteria. We aimed to study the impact of the new definition on the epidemiology of fatty liver disease. METHODS: We randomly selected 1013 adults from the Hong Kong census database for clinical assessment, proton-magnetic resonance spectroscopy, and transient elastography. Five hundred sixty-five subjects without fatty liver at baseline underwent follow-up assessment. MAFLD was diagnosed as intrahepatic triglyceride content (IHTG) >= 5% and the presence of overweight/obesity, diabetes, or two other metabolic risk factors, with and without concomitant liver diseases. The diagnosis of NAFLD required the exclusion of concomitant liver diseases; metabolic factors were not considered. RESULTS: The population prevalence of MAFLD and NAFLD was 25.9% (95% CI 23.2-28.7%) and 25.7% (95% CI 23.1-28.5%), respectively. Among 277 subjects with IHTG >= 5%, 247 (89.2%) fulfilled both the definitions of MAFLD and NAFLD. Fourteen subjects (5.1%) had IHTG >= 5% but did not meet the metabolic criteria of MAFLD. The incidence of MAFLD was 2.8 per 100 person-years at a median interval of 47 months (range 34-60 months). Among 78 subjects with incident NAFLD, 59 (75.6%) met the criteria of MAFLD; only one of the latter, a regular drinker, had liver stiffness >= 10 kPa. CONCLUSIONS: The new definition of MAFLD does not significantly change the prevalence compared with NAFLD, but it may reduce the incidence by 25%. People with hepatic steatosis but not fulfilling the definition of MAFLD unlikely have significant liver disease.