BACKGROUND

Although the metabolic score for insulin resistance (METS-IR) is significantly associated with metabolic disorders, its dose-response relationship with nonalcoholic fatty liver disease (NAFLD) remains inconclusive. This study aimed to investigate the dose-response relationship between the metabolic score for insulin resistance and NAFLD, and to identify its inflection point.

METHODS

This cross-sectional study evaluated the association between METS-IR and NAFLD using multivariable logistic regression applied to data from the 2017-2020 US National Health and Nutrition Examination Survey. Non-linear dynamics were investigated through smoothing spline models and segmented regression. Subgroup comparisons were performed, and diagnostic accuracy was assessed using interaction tests and receiver operating characteristic (ROC) analysis.

RESULTS

Among 2,486 eligible participants, 804 (32.34%) were diagnosed with NAFLD. Adjusted regression models revealed a 7% increase in NAFLD likelihood per unit rise in METS-IR (odds ratio [OR] = 1.07, 95% confidence interval [CI]: 1.04-1.10; P < 0.001). Non-linear modeling identified a saturation effect with an inflection point at 46.73 units. Subgroup stratification demonstrated consistent associations across demographic categories (P > 0.05). The diagnostic performance analysis yielded an area under the curve value of 0.861 in the fully adjusted models.

CONCLUSIONS

The results of this study confirmed a non-linear dose-response association between METS-IR and NAFLD. Determining the METS-IR may enhance the identification of early-stage NAFLD in clinical and public health settings.