The Impact of Insulin Resistance on Hepatic Fibrosis among United States Adults with Non-Alcoholic Fatty Liver Disease: NHANES 2017 to 2018

BACKGROUND: We aimed to investigate the association of hepatic steatosis with liver fibrosis and to assess the interactive effects of hepatic steatosis and insulin resistance on liver fibrosis in a nationally representative sample of United States adults. METHODS: We conducted a cross-sectional analysis using data from National Health and Nutrition Examination Survey 2017 to 2018, which for the first time included transient elastography to assess liver stiffness and hepatic steatosis. We evaluated the association between hepatic steatosis (using controlled attenuation parameter [CAP]) and clinically significant liver fibrosis (defined as liver stiffness ≥7.5 kPa) using logistic regression with an interaction term for hepatic steatosis and insulin resistance (defined as homeostatic model assessment of insulin resistance ≥3.0). RESULTS: Among adults undergoing transient elastography (n=2,023), 45.9% had moderate or greater hepatic steatosis and 11.3% had clinically significant liver fibrosis. After adjustment for demographic and metabolic factors, the odds of significant liver fibrosis increased as CAP score rose (odds ratio, 1.35 per standard deviation increment; 95% confidence interval, 1.11 to 1.64). We detected a significant interaction effect between CAP score and insulin resistance on the probability of significant liver fibrosis (P=0.016 for interaction). The probability of significant liver fibrosis increased in the presence of insulin resistance with increasing CAP score, while those without insulin resistance had low probability of significant liver fibrosis, even with high CAP scores. CONCLUSION: Individuals with hepatic steatosis had higher odds of fibrosis when insulin resistance was present. Our findings emphasize the importance of the metabolic aspects of the disease on fibrosis risk and suggest a need to better identify patients with metabolic associated fatty liver disease.