Association between the Modified Cardiometabolic Index and Endometriosis in an American Cohort: Insights from a Cross-sectional Analysis

The modified cardiometabolic index (MCMI), an integrated measure of visceral fat and lipid metabolism, has been widely applied in metabolic disease research. However, its relationship with endometriosis has not been thoroughly investigated. Data were obtained from the 1999-2006 NHANES surveys. Endometriosis was identified through self-reported diagnosis. MCMI was calculated as ln (TG × glucose / HDL-C) × waist / height. Weighted multivariable logistic regression models were used to examine the association between MCMI and endometriosis. Restricted cubic spline (RCS) models were applied to assess potential non-linear relationships. Subgroup analyses were performed to assess whether the association was consistent across population subgroups. A sensitivity analysis using propensity score matching (PSM) was also conducted to evaluate the robustness of the results. After adjustment for all covariates, higher MCMI was significantly associated with the presence of endometriosis (OR = 1.58, 95% CI: 1.16-2.15; P = 0.004). Participants in the highest MCMI tertile had 99% higher odds of endometriosis compared with those in the lowest tertile (OR = 1.99, 95% CI: 1.10-3.62; P = 0.02). A significant increasing trend was observed across tertiles (P for trend = 0.03). RCS analysis confirmed a positive linear association (P for overall effect = 0.004; P for nonlinearity = 0.20). Subgroup analyses revealed no significant interactions, and the sensitivity analysis confirmed the robustness of the association. Higher MCMI was significantly associated with endometriosis, supporting its potential utility as a simple, non-invasive biomarker. Further research using clinically confirmed diagnoses and longitudinal designs is needed to clarify this association.