Non-alcoholic fatty liver disease (NAFLD) and metabolic associated fatty liver disease (MAFLD) demonstrate highly similar clinical courses and mortality rates, and a name change may not be clinically beneficial, based on data from more than 17,000 patients.
Instead, etiologic subcategorization of fatty liver disease (FLD) should be considered, reported lead author Zobair M. Younossi, MD, of Betty and Guy Beatty Center for Integrated Research, Inova Health System, Falls Church, Va., and colleagues.
“There is debate about whether NAFLD is an appropriate name as the term ‘non-alcoholic’ overemphasizes the absence of alcohol use and underemphasizes the importance of the metabolic risk factors which are the main drivers of disease progression,” the investigators wrote in Hepatology. “It has been suggested that MAFLD may better reflect these risk factors. However, such a recommendation is made despite a lack of a general consensus on the definition of ‘metabolic health’ and disagreements in endocrinology circles about the term ‘metabolic syndrome.’ Nevertheless, a few investigators have suggested that MAFLD but not NAFLD is associated with increased fibrosis and mortality.”
To look for clinical differences between the two disease entities, Dr. Younossi and colleagues turned to the National Health and Nutrition Examination Survey (NHANES). Specifically, the NHANES III and NHANES 2017-2018 cohorts were employed, including 12,878 and 4,328 participants, respectively.
MAFLD was defined as FLD with overweight/obesity, evidence of metabolic dysregulation, or type 2 diabetes mellitus. NAFLD was defined as FLD without excessive alcohol consumption or other causes of chronic liver disease. Patients were sorted into four groups: NAFLD, MAFLD, both disease types, or neither disease type. Since the categories were not mutually exclusive, the investigators compared clinical characteristics based on 95% confidence intervals. If no overlap was found, then differences were deemed statistically significant.
Diagnoses of NAFLD and MAFLD were highly concordant (kappa coefficient = 0.83-0.94). After a median of 22.8 years follow-up, no significant differences were found between groups for cause-specific mortality, all-cause mortality, or major clinical characteristics except those inherent to the disease definitions (for example, lack of alcohol use in NAFLD). Greatest risk factors for advanced fibrosis in both groups were obesity, high-risk fibrosis, and type 2 diabetes mellitus.
As anticipated, by definition, alcoholic liver disease and excess alcohol use were documented in approximately 15% of patients with MAFLD, but in no patients with NAFLD. As such, alcoholic liver disease predicted liver-specific mortality for MAFLD (hazard ratio, 4.50; 95% confidence interval, 1.89-10.75) but not NAFLD. Conversely, insulin resistance predicted liver-specific mortality in NAFLD (HR, 3.57; 95% CI, 1.35-9.42) but not MAFLD (HR, 0.84; 95% CI, 0.36-1.95).
“These data do not support the notion that a name change from NAFLD to MAFLD will better capture the risk for long-term outcomes of these patients or better define metabolically at-risk patients who present with FLD,” the investigators concluded. “On the other hand, enlarging the definition to FLD with subcategories of ‘alcoholic,’ ‘non-alcoholic,’ ‘drug-induced,’ etc. has merit and needs to be further considered. In this context, a true international consensus group of experts supported by liver and non-liver scientific societies must undertake an evidence-based and comprehensive approach to this issue and assess both the benefits and risks of changing the name.”
Dr. Rohit Loomba
According to Rohit Loomba, MD, director of the NAFLD research center and professor of medicine in the division of gastroenterology and hepatology at University of California, San Diego, the study offers a preview of the consequences if NAFLD were changed to MAFLD, most notably by making alcohol a key driver of outcomes.
“If we change the name of a disease entity ... how does that impact natural history?” Dr. Loomba asked in an interview. “This paper gives you an idea. If you start calling it MAFLD, then people are dying from alcohol use, and they’re not dying from what we are currently seeing patients with NAFLD die of.”
He also noted that the name change could disrupt drug development and outcome measures since most drugs currently in development are directed at nonalcoholic steatohepatitis (NASH).
“Is it worth the headache?” Dr. Loomba asked. “How are we going to define NASH-related fibrosis? That probably will remain the same because the therapies that we will use to address that will remain consistent with what we are currently pursuing. ... It’s probably premature to change the nomenclature before assessing the impact on finding new treatment.”
Dr. Younossi disclosed relationships with BMS, Novartis, Gilead, and others. Dr. Loomba serves as a consultant to Aardvark Therapeutics, Altimmune, Anylam/Regeneron, Amgen, Arrowhead Pharmaceuticals, AstraZeneca, Bristol-Myer Squibb, CohBar, Eli Lilly, Galmed, Gilead, Glympse bio, Hightide, Inipharma, Intercept, Inventiva, Ionis, Janssen, Madrigal, Metacrine, NGM Biopharmaceuticals, Novartis, Novo Nordisk, Merck, Pfizer, Sagimet, Theratechnologies, 89 bio, Terns Pharmaceuticals, and Viking Therapeutics.