Lipid accumulation product and endometriosis in women aged 18 years and older: A cross-sectional study of NHANES 1999 to 2006

Endometriosis, a chronic gynecological disorder, is increasingly linked to metabolic dysregulation. The lipid accumulation product (LAP) - a biomarker integrating waist circumference and triglycerides - may provide additional information on this association but remains insufficiently studied. We aimed to assess the association between LAP and endometriosis in a nationally representative cohort. Analyzing 1999 to 2006 National Health and Nutrition Examination Survey data from 1792 women with self-reported endometriosis status, we calculated LAP as (waist circumference [cm] - 58) × (triglycerides [mmol/L]). Multivariable logistic regression evaluated linear associations, while restricted cubic splines and threshold analyses assessed nonlinearity. Subgroup interactions were tested via stratified models. Women in the highest LAP quartile exhibited 70% greater endometriosis odds than the lowest quartile (odds ratio = 1.70, 95% confidence interval = 1.03-2.81, P < .05). Restricted cubic spline analyses supported an approximately linear dose-response pattern across the LAP distribution, with higher LAP values associated with progressively greater odds of endometriosis (P < .001). While most subgroups showed consistent associations, exploratory subgroup analyses suggested that the LAP-endometriosis association was stronger among women with a history of stroke (P < .05). Higher LAP values were associated with higher odds of endometriosis in this cross-sectional sample, with odds increasing progressively across the LAP distribution. LAP may be considered a potentially useful marker for metabolic risk stratification in women with possible endometriosis, but its clinical utility requires confirmation in prospective studies.