Mediating Role of Depression in the Association Between the Body Roundness Index and Female Infertility: A Cross‐Sectional Study Using Data From the National Health and Nutrition Examination Survey ( <scp>NHANES</scp> ) 2013–2018

BACKGROUND: Obesity and depression critically impact infertility, with Body Roundness Index (BRI) superseding BMI in assessing visceral adiposity by quantifying abdominal fat's metabolic dysregulation. Depression-infertility links involve physiological-behavioral mechanisms and psychosocial stigma, affecting 12.7% of US reproductive-age women. Longitudinal studies and integrated interventions combining precision diagnostics, metabolic optimization, and mental health are imperative to address multifactorial. METHODS: This cross-sectional study analyzed 4429 women aged 18-45 from NHANES (2013-2018) to investigate depression-infertility associations, defining infertility as ≥ 1 year of unsuccessful pregnancy attempts. Depression severity was quantified using PHQ-9 scores (0-27). Through multivariate logistic regression and subgroup analyses stratified by age and race/ethnicity, nonlinear relationships were examined via smoothed curve fitting and threshold effect analysis. The findings systematically revealed significant correlations between depressive symptoms and infertility risks, emphasizing mental health's role in reproductive outcomes while controlling for demographic confounders. RESULTS: Among the participants, 527 women (11.89%) were diagnosed with infertility. A statistically significant positive correlation was observed between the BRI and infertility risk, with higher BRI values associated with increased infertility incidence (p < 0.001). Mediation analysis indicated that the PHQ-9 score mediated 4.46% of the total effect between BRI and infertility in the overall population, with a stronger mediating effect (9.13%) among participants with BRI > 5.2. CONCLUSION: This NHANES-based study demonstrates a significant association between elevated BRI and female infertility, with depressive symptoms partially mediating this relationship, particularly in high-BRI subgroups.