Conicity index increases the risk of female infertility: An analysis of NHANES 2013 to 2018

Abstract

This study investigates the association between anthropometric indices and infertility in women of childbearing age. : The original data of women aged 20 to 45 years were obtained from National Health and Nutrition Examination Survey (NHANES) 2013 to 2018 for the present cross-sectional study. Data of reproductive status was defined according to answer to Reproductive Health Questionnaire. Each participant's anthropometric indices were calculated according to the formulas. Weighted logistic regression analysis, sensitivity analysis, subgroup analysis, smooth curve fitting and receiver-operating characteristic curve analysis were employed to investigate the association between anthropometric indices and infertility. A total of 2948 females aged 20 to 45 years were included and analyzed, with 337 (11.43%) self-reported infertility. Weighted logistic regression analysis linked conicity index (C-index) to infertility after adjusting for potential confounders, with an OR of 35.95 (95% CI: 6.50-198.95). Compared with the lowest tertile (T1), the third tertile (T3) of C-index was positively correlation with infertility, with an OR of 2.21 (95% CI: 1.47-3.33). Subgroup analysis showed that C-index tended to be associated with infertility in all participants aged 20 to 45 years. Smoothed curve fitting showed a positive linear relationship between C-index and infertility. Compared with other obesity indicators, C-index (AUC = 0.608) also shows good predictive performance for infertility. These differences were statistically significant (all P < .05). Our study showed that C-index had a stronger connection with the risk of infertility than other markers of obesity including body mass index (BMI), relative fat mass (RFM) and waist-to-height ratio (WHTR), and managing obesity as determined by C-index may help to reduce the risk of infertility.

Keywords: NHANES; body mass index; conicity index; infertility; relative fat mass; waist-to-height ratio.

Figure 1.

Flowchart of participants selection from NHANES 2013–2018. NHANES = National Health and Nutrition Examination Survey.

Figure 2.

Relationship of anthropometric indices with the risk of infertility for all females and for subgroups of aged. (A1, B1, C1, D1) Dose–response relationship between BMI, C-index, RFM, WHTR and risk of infertility in all females respectively. (A2, B2, C2, D2) Dose–response relationship between BMI, C-index, RFM, WHTR and risk of infertility in females grouped by aged respectively. BMI = body mass index, C-index = conicity index, RFM = relative fat mass, WHTR = waist-to-height ratio.

Figure 3.

ROC curve analyses to predict infertility. (A) ROC to predict infertility for all female participants. (B and C) ROC to predict infertility for female participants under and over 30 years old. BMI = body mass index, C-index = conicity index, RFM = relative fat mass, ROC = receiver-operating characteristic, WHTR = waist-to-height ratio.