Association between depression and infertility risk among American women aged 18–45 years: the mediating effect of the NHHR
Authors: Yang QiaoRui , Tao Jing , Xin Xin , Zhang JinFu , Fan ZhenLiang 
Published: June 2024

Abstract
Background/Objective
Depression and infertility are major medical and social problems. The non-high-density lipoprotein cholesterol to high-density lipoprotein cholesterol ratio (NHHR) serves as an innovative and reliable lipid marker for cardiovascular disease risk assessment. Previous research has indicated a potential correlation among lipid metabolism, depression, and infertility. Nonetheless, the exact involvement of lipid metabolism in modulating the pathological mechanisms associated with depression-induced infertility remains to be fully elucidated. The aim of this study was to explore the connection between depression and infertility and to assess whether the NHHR mediates this association.

Methods
A cross-sectional analysis was performed utilizing data from there cycles (2013–2018) of the National Health and Nutrition Examination Survey (NHANES) database. Female infertility was assessed according to the responses to the RHQ074 question in the reproductive health questionnaire module. Depression states were evaluated using the Patient Health Questionnaire-9 and classified into three grades based on the total scores: no depression (0–4 points), minimal-to-mild depression (5–9 points) and moderate-to-severe depression (10 or more points). The NHHR was calculated from laboratory cholesterol test results. Baseline population characteristics were compared, and subgroup analyses were carried out based on the stratification of age and body mass index (BMI). Weighted multivariable logistic regression and linear regression models, with adjustments for various covariables, were employed to examine the associations among depression, infertility and the NHHR. Finally, mediation analysis was utilized to explore the NHHR's potential mediating role in depression states and female infertility.

Results
Within this cross-sectional study, 2,668 women aged 18 to 45 years residing in the United States were recruited, 305 (11.43%) of whom experienced infertility. The study revealed a markedly higher prevalence of depression (P = 0.040) and elevated NHHR (P < 0.001) among infertile women compared to the control cohort. Furthermore, moderate-to-severe depression states independently correlated with increased infertility risk, irrespective of adjustments for various covariables. Subgroup analysis indicated a positive association between depression and infertility risk within certain age categories, although no such relationship was observed within subgroups stratified by BMI. The findings from the weighted logistic regression analysis demonstrated that the elevated NHHR is positively associated with heightened infertility risk. Additionally, the weighted linear regression analysis indicated that moderate-to-severe depression is positively linked to the NHHR levels as well. Finally, the association between depression states and female infertility was partially mediated by the NHHR, with the mediation proportion estimated at 6.57%.

Conclusion
In the United States, depression is strongly correlated with an increased likelihood of infertility among women of childbearing age, with evidence suggesting that this relationship is mediated by the NHHR. Subsequent research efforts should further explore the underlying mechanisms connecting depression and infertility.