Association Between Remnant Cholesterol and Endometriosis Findings from NHANES 1999–2006

Background: Endometriosis is a chronic gynecological disorder causing significant morbidity and health burden. Recent evidence suggests that lipid metabolism, particularly remnant cholesterol (RC), may be involved in its development. RC-the cholesterol content of triglyceride-rich lipoproteins (TGRLs), including chylomicrons, very low-density lipoproteins (VLDL), and intermediate-density lipoproteins (IDL). Elevated RC is closely associated with arteriosclerosis and increased cardiovascular disease incidence, making it a valuable biomarker for assessing cardiovascular health. This study explores the association between RC levels and endometriosis prevalence in a representative sample of women. Methods: Using cross-sectional data from NHANES (1999-2006), we analyzed 1,979 women aged 20-54 years. Weighted logistic regression models were applied to assess the relationship between RC and endometriosis. Three models were used: unadjusted (Model 1), adjusted for age, ethnicity, education, and marital status (Model 2), and fully adjusted for additional variables (Model 3). Subgroup analyses and smoothing curve fitting were also performed. Results: Elevated RC levels were significantly associated with higher endometriosis prevalence across all models. Each 1 mg/dL above the mean level of RC was linked to a 2.3% higher incidence of endometriosis (Model 1: OR 1.023, 95% CI 1.009-1.036, p = 0.001; Model 2: OR 1.022, p = 0.004; Model 3: OR 1.023, p = 0.022). Individuals in the highest RC tertile had a higher incidence of endometriosis compared to the lowest tertile (OR 1.833, p for trend = 0.077). A linear dose-response relationship was identified, with no threshold or saturation effects. Conclusion: The study indicates a strong correlation between elevated RC levels and increased endometriosis incidence, highlighting the potential role of lipid metabolism in endometriosis development.