Composite cardiovascular health indices (Life's essential 8 and Life's crucial 9) and female infertility: an NHANES 2013-2018 cross-sectional analysis.

Background: Female infertility affects 10-15% of couples worldwide and is influenced by multiple factors, including cardiovascular and metabolic health. This study examines the association between composite cardiovascular health indices-Life's Essential 8 (LE8) and Life's Crucial 9(LC9)-and the risk of infertility. Methods: We conducted a cross-sectional analysis of NHANES 2013-2018 data on 2,360 women aged 20-45 years, incorporating the NHANES complex survey design weights. We used survey-weighted multivariable logistic regression, restricted cubic splines (RCS), and subgroup/interaction analyses. For prediction, we applied LASSO with 10-fold cross-validation, followed by multivariable logistic regression to construct a nomogram. Discrimination (AUC with 95% CI), bootstrap calibration (1,000 resamples), and decision curve analysis (DCA) were reported. Results: In fully adjusted models, women in the highest quartile of LE8 had lower odds of infertility than those in the lowest quartile (OR 0.39, 95% CI 0.26-0.58), and similarly for LC9 (OR 0.43, 95% CI 0.29-0.65; p-trend < 0.001). The prediction nomogram showed moderate discrimination (AUC 0.691, 95% CI 0.668-0.714) with good internal calibration; no external validation was performed. Conclusion: Better composite cardiovascular health-captured by LE8 and LC9-is associated with lower prevalence of self-reported infertility. This cross-sectional design precludes causal inference. Given the nomogram's moderate AUC and lack of external validation, the model's clinical utility is limited. Prospective studies are warranted.