Endometriosis and Early-Onset Cardiovascular Disease Across Levels of Systemic Inflammation: A Cross-Sectional Study of NHANES 1999-2006

Abstract Background: Endometriosis is a chronic gynecologic condition which has been linked with higher cardiovascular disease (CVD) risk. Although systemic inflammation is central to endometriosis and CVD pathophysiology, it remains unclear whether endometriosis is associated specifically with early-onset CVD and whether systemic inflammation modifies this association. Methods: This was a cross-sectional study of 5,345 women aged 20-54 years from the National Health and Nutrition Examination Survey (1999-2006). Endometriosis and early-onset CVD were self-reported. Early-onset CVD was defined as a composite measure of coronary heart disease, angina/angina pectoris, heart attack, congestive heart failure, or stroke. Systemic inflammation was measured using C-reactive protein [CRP; low/moderate (≤ 3 mg/L) and high (>3mg/L)] and the systemic immune-inflammation index (SII; tertiles). Survey-weighted logistic regression was used to assess associations and heterogeneity by systemic inflammation, with stabilized inverse probability weighting (IPW) to adjust for confounding. Results: Of the 5,435 women, 370 (6.9%) reported an endometriosis diagnosis and 162 (3.0%) early-onset CVD. After IPW adjustment for age, body mass index, smoking status, education, age at menarche, physical activity and race/ethnicity, endometriosis was associated with higher odds of early-onset CVD (prevalence odds ratio [POR] = 1.91, 95% CI: 1.23-2.97). This association was strongest among women with high CRP (POR= 2.33, 95% CI: 1.49-3.66), but not among those with low/moderate CRP levels (p-interaction= 0.086). Across SII strata, the strongest association was observed among women in the medium SII tertile (POR = 2.92, 95% CI: 1.47-5.78), with no associations in the low or high tertiles (p-interaction = 0.288). Conclusion: Endometriosis was associated with higher odds of early-onset CVD in this nationally representative sample of U.S. women. Although the strength of the association varied across CRP and SII strata, formal tests for interaction were not statistically significant. These findings should be understood as exploratory and require further investigation in prospective studies Competing Interest Statement The authors have declared no competing interest. Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The study used only publicly available data from the National Health and Nutrition Examination Survey (NHANES), 1999-2006, conducted by the National Center for Health Statistics, Centers for Disease Control and Prevention. Public-use NHANES data and documentation are available from the NCHS NHANES website. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Data Availability The data used in this study are publicly available from the National Health and Nutrition Examination Survey (NHANES), administered by the National Center for Health Statistics, Centers for Disease Control and Prevention. Data from the 1999-2006 survey cycles, including questionnaires, examination data, laboratory data, and documentation, are publicly available through the NHANES website.