Non‐alcoholic fatty liver disease as an independent manifestation of the metabolic syndrome: Results of a US national survey in three ethnic groups

Background and Aim The metabolic syndrome ( MetS ) and each of its components are strongly associated with non‐alcoholic fatty liver disease ( NAFLD ). This has led many investigators to suggest that NAFLD is an independent component of the MetS . We formally tested this hypothesis using confirmatory factor analysis, which allows comparison of different models, with or without including NAFLD as a component of the MetS . Methods We analyzed data from 3846 subjects of the T hird N ational H ealth and N utrition E xamination S urvey (1988–1994). NAFLD was defined by increased liver fat measured by ultrasonography. Results MetS by A dult T reatment P anel III criteria was present in 20.5%, and 30.2% had NAFLD , defined as mild, moderate, or severe ultrasonographic steatosis. Using confirmatory factor analysis, a basic model representing the MetS using its currently accepted components (glucose, waist, triglyceride/high‐density lipoprotein ratio, and mean arterial pressure) showed excellent goodness‐of‐fit statistics. Addition of NAFLD to the model as a fifth independent variable decreased model fit, suggesting that NAFLD is not an additional independent component of the MetS . Analysis by ethnicity showed that addition of NAFLD decreased model fit in W hites but resulted in minor improvements in non‐ H ispanic B lacks and M exican A mericans. Conclusions The MetS is strongly associated with NAFLD . However, we found no evidence that NAFLD is an independent component or manifestation of the MetS . Interestingly, ethnic differences might be important in this relationship and require further study.