Prevalence, characteristics, and mortality outcomes of obese and nonobese MAFLD in the United States

Background and aims Metabolic dysfunction-associated fatty liver disease (MAFLD) establishes new criteria for diagnosis of fatty liver disease independent of alcohol intake. We aimed to describe the prevalence and compare characteristics and mortality outcomes of persons with nonobese and obese MAFLD. Methods Using data from 13,640 participants from the third National Health and Nutrition Examination Survey (NHANES III) 1988-1994, we identified participants with fatty liver on ultrasound who had MAFLD and analyzed them by the presence of obesity. Results Overall prevalence of MAFLD was 19%; amongst those, 54% were obese and 46% were nonobese. Nonobese MAFLD was more common in participants older than 65 than in younger participants (56.8% vs. 43.2%, p < 0.0001). Nonobese MAFLD was more common in males (63.2% vs. 48.3%, p < 0.0001). Obese MAFLD was more common in females (51.7% vs. 48.3%, p < 0.0001). After adjusting for several demographic factors and alcohol use, older age [adjusted odds ratio (aOR) 1.02, 95% CI 1.00-1.02, p = 0.003] and being male (aOR: 1.65, 95% CI 1.25-2.17, p = 0.001) were independent risk factors for nonobese MAFLD. Nonobese MAFLD participants had a higher 20-year cumulative incidence for all-cause mortality compared to obese MAFLD participants (33.2% vs. 28.8%, p = 0.0137). However, nonobese MAFLD was not independently associated with mortality after adjusting for relevant confounders, while FIB-4 > 1.3 and cardiovascular disease were the strongest risk factors associated with increased mortality [adjusted hazard ratio (aHR) > 2.7 for both, p < 0.0001 for both]. Conclusions Nonobese MAFLD constitutes about half of the MAFLD in the United States, especially among males and the elderly. Notably, nonobese MAFLD carries higher mortality than obese MAFLD. Screening and diagnosis of MAFLD should be considered in nonobese populations.