The main findings of the present study are: 1) The prevalence of NAFLD and MAFLD in the contemporary US population is high at ~ 35%-40%, with Hispanics being more commonly affected, as recently shown; 2) The two definitions have a high degree of concordance; 3) There is a small minority of metabolically healthy normal-weight individuals with NAFLD and they seem to have a low risk of advanced fibrosis 4) The prevalence of advanced liver fibrosis is similar in patients with MAFLD and NAFLD.
Using data from NHANES III (1988–1994), Lin et al recently showed a similar prevalence of ultrasound-diagnosed NAFLD (31.2%) and MAFLD (33.2%). In their analysis, however, ~5% of patients with NAFLD did not meet MAFLD criteria (an estimate that is double compared to our study). We believe that this difference is mainly attributable to the number of normal-weight participants being higher in 1988–1994 (44%), compared with 2017–2018 (26.9%). Moreover, the authors showed a higher prevalence of advanced fibrosis in MAFLD compared with NAFLD based on non-invasive scores, a finding that we did not replicate in the present VCTE-based study. It should be stressed that the overall concordance between the two definitions is likely to be affected by the prevalence of overweight-obesity, type 2 diabetes (an important risk factor for advanced fibrosis) and different aetiologies of liver disease such as viral hepatitis and significant alcohol consumption in the studied population. For example, agreement was much lower in a recent study from Japan.
Our study has several limitations. Firstly, we could only estimate the prevalence of steatosis and fibrosis as the gold-standard technique (liver biopsy) is not well suited for large population-based studies. Secondly, there are no universally accepted cut-offs for CAP and LSM. We used the ones proposed by Eddowes et al since they were derived from a large cohort in a western country.
In conclusion, the overall concordance of diagnostic criteria for NAFLD and MAFLD is high in the US population, characterized by a high prevalence of overweight-obesity and type 2 diabetes, and advanced fibrosis occurs in a similar proportion of patients with each condition.
CAP, Controlled Attenuation Parameter; MAFLD, metabolic associated fatty liver disease; NAFLD, non-alcoholic fatty liver disease; NHANES, National Health and Nutrition Examination Survey.
The manuscript was written by the authors without any external writing assistance.
Data Availability Statement
All data used in the present study are publicly available at theNHANES website.
Liver International. 2021;41(6):1290-1293. © 2021 Blackwell Publishing