Systematically comparing epidemiological and clinical features of MAFLD and NAFLD by meta-analysis: Focusing on the non-overlap groups

Background & Aims The applicability of the novel metabolic dysfunction associated fatty liver disease (MAFLD) definition has been studied in numerous cohorts and compared to non-alcoholic fatty liver disease (NAFLD). No consensus has been reached on which definition is preferred. Therefore, this meta-analysis aims to compare the epidemiological and clinical features of NAFLD and MAFLD in the general and non-general population. Methods We searched Medline, Embase and Web of Science for studies comparing MAFLD to NAFLD. Based on MAFLD and NAFLD status, the following subgroups were investigated for liver health: overlap fatty liver disease (FLD), NAFLD-only and MAFLD-only. Data were pooled using random-effects models. Results We included 17 studies comprising 9 808 677 individuals. In the general population, MAFLD was present in 33.0% (95% CI 29.7%-36.5%) and NAFLD in 29.1% (95% CI 27.1%-31.1%). Among those with FLD, 4.0% (95% CI 2.4%-6.4%) did not meet the MAFLD criteria but had NAFLD (NAFLD-only) and 15.1% (95% CI 11.5%-19.5%) was exclusively captured by the novel MAFLD definition (MAFLD-only). Notably, this MAFLD-only group was at significantly increased risk for fibrosis (RR 4.2; 95% CI 1.3-12.9) and had higher alanine aminotransferase (mean difference: 8.0 U/L, 95% CI 2.6-13.5) and aspartate aminotransferase (mean difference: 6.4 U/L, 95% CI 3.0-9.7), compared to NAFLD-only. Similar results were obtained among the non-general population. Conclusions Metabolic dysfunction associated fatty liver disease and NAFLD are highly prevalent in the general population, with considerable overlap between them. However, compared to NAFLD, significantly more individuals were additionally identified by MAFLD than were missed. Importantly, by using the MAFLD criteria, more individuals with liver damage were identified. Therefore, the novel MAFLD definition is superior to NAFLD on a population level.