Hokyou Lee^∗, Yong-ho Lee^‡,§, Seung Up Kim^‡,||, Hyeon Chang Kim^∗

^∗Department of Preventive Medicine, Yonsei University College of Medicine, Seoul, Korea
^‡Department of Internal Medicine, Yonsei University College of Medicine, Seoul, Korea
^§Institute of Endocrine Research, Yonsei University College of Medicine, Seoul, Korea
^||Yonsei Liver Center, Severance Hospital, Seoul, Korea

Reprint requests Address requests for reprints to: Hyeon Chang Kim, MD, PhD, Department of Preventive Medicine, Yonsei University College of Medicine, 50-1 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea.

Seung Up Kim, MD, PhD, Department of Internal Medicine, Yonsei University College of Medicine, 50-1 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea. 

Yong-ho Lee, MD, PhD, Department of Internal Medicine, Yonsei University College of Medicine, 50-1 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea

Background & Aims
An international expert panel proposed a new definition for metabolic dysfunction–associated fatty liver disease (MAFLD) as a name change from nonalcoholic fatty liver disease (NAFLD). The clinical impact of this change on the assessment of cardiovascular disease (CVD) risk is yet unknown. We evaluated the prevalence of fatty liver disease (FLD) and the associated CVD risk using each of these definitions.

Methods
From a nationwide health screening database, we included 9,584,399 participants (48.5% male) aged 40-64 years between 2009 and 2010. Participants were categorized by presence of NAFLD and MAFLD, separately, and by the combination of the 2 definitions—Neither-FLD, NAFLD-only, MAFLD-only, or Both-FLD. The primary outcome was a composite CVD event, including myocardial infarction, ischemic stroke, heart failure, or CVD-related death.

Results
The prevalence of NAFLD and MAFLD was 28.0% and 37.3%, respectively. After excluding those with prior CVD, 8,962,813 participants were followed for a median of 10.1 years. NAFLD and MAFLD were each associated with significantly higher risk for CVD events. When the Neither-FLD group was the reference, multivariable-adjusted hazard ratios (95% confidence interval) for CVD events were 1.09 (1.03-1.15) in the NAFLD-only group, 1.43 (1.41-1.45) in the MAFLD-only group, and 1.56 (1.54-1.58) in the Both-FLD group.

Conclusions
A considerable proportion of middle-aged Korean adults have MAFLD without satisfying the former definition of NAFLD. The change from NAFLD to MAFLD criteria may identify a greater number of individuals with metabolically complicated fatty liver and increased risk for CVD.