Risk Factors for Infertility in Korean Women

Anti-infertility roles of flavonoids: insights into the female reproductive system

Female infertility is a complex and multifactorial disease affecting millions of women worldwide, wherein oxidative stress and inflammation play major roles in its pathophysiology. Flavonoids, a class of polyphenolic compounds derived from plants, show promise in alleviating infertility-related disorders such as polycystic ovary syndrome (PCOS), endometriosis, and uterine implantation abnormalities. The antioxidant and anti-inflammatory properties of flavonoids can be useful in overcoming oxidative damage and disturbances of inflammatory conditions within the reproductive system. Key flavonoids, including quercetin and apigenin, have demonstrated the ability to regulate hormonal imbalances, enhance follicular development, and improve oocyte quality. Flavonoids may also act by interacting with essential inflammatory and hormonal pathways to suppress the synthesis of pro-inflammatory cytokines while increasing antioxidant defenses. The integration of flavonoid-based strategies with conventional treatments opens up promising avenues in improving reproductive outcomes and advancing fertility therapies. This review will highlight the molecular mechanisms underlying the efficacy of flavonoids and point out their potential as nutraceutical interventions in the management of female infertility.

Lifestyle factors and health outcomes associated with infertility in women: A case-control study using National Health Insurance Database

BACKGROUND

Approximately one in six people is experiencing infertility at some point in their lives. In response, health insurance coverage for infertility treatments has been strengthened. However, studies examining lifestyle factors that affect infertility remain lacking, highlighting the need to generate objective evidence to address infertility issues using national-level datasets.

METHODS

The General Healthcare Screening Program dataset from National Health Insurance Service database was employed in this study to examine infertility and childbirth among women aged 22-49 years. In 2020, 25,333 women with infertility and 73,759 women who had given birth were initially identified. After applying propensity score matching for age, Charlson Comorbidity Index score, and income level, the final study population included 24,325 women with infertility and 24,325 women who with childbirth. Employing a case-control study design, lifestyle factors (drinking, smoking, and physical activity) and health checkup outcomes (underweight, overweight, hypertension, diabetes, kidney function, anemia, and menstrual disorders) were assessed in this study. Statistical analyses included chi-squared tests, t-tests, and logistic regression.

RESULTS

This study revealed significant risk factors for infertility: two high-risk lifestyle factors, including heavy drinking and smoking, and five health conditions, comprising underweight, hypertension, diabetes, kidney function loss, and menstrual disorders. Conversely, being overweight, not engaging in vigorous physical activity, and anemia were negatively associated with infertility.

CONCLUSIONS

These findings underscore the need for lifestyle modifications and personalized preconception care to improve fertility outcomes.

TRIAL REGISTRATION

Not available.

Association between combined healthy lifestyles and infertility: a cross-sectional study in US reproductive-aged women

BACKGROUND

Infertility is a widespread problem for couples worldwide, and lifestyle factors are the cornerstone of infertility prevention. This research seeks to explore the association between combined healthy lifestyles and infertility risk among women of reproductive age.

METHODS

This study analyzed data from the National Health and Nutrition Examination Survey (NHANES, 2013-2018), concentrating on 2,154 women aged 18 to 44. A healthy lifestyle score was created based on healthy diet (top two-fifths of the Healthy Eating Index-2015 score), low-to-moderate alcohol drinking (1-14 g/day), optimal waist circumference (less than 80 cm), adequate physical activity (at least 150 min of moderate-to-vigorous leisure-time exercise per week), and current nonsmoking. Weighted logistic regression analysis was applied to assess the link between healthy lifestyle scores and the risk of infertility, adjusting for potential confounders.

RESULTS

After adjusting for potential confounders, women exhibiting 4 to 5 healthy lifestyle factors demonstrated a 59% decrease in the likelihood of infertility (OR: 0.41, 95% CI: 0.23-0.76) relative to those with 0 to 1 healthy lifestyle factors. Additionally, each increment in healthy lifestyle factors corresponded to a 21% decrease in infertility risk (OR: 0.79, 95% CI: 0.68-0.92). Analysis of subgroups indicated that the inverse association was more pronounced in females younger than 30. Additionally, optimal waist circumference is the foremost factor contributing to this inverse relationship.

CONCLUSION

Adhering to healthy lifestyles significantly lowers the likelihood of infertility among reproductive-aged women. Public health initiatives could consider enhancing access to healthy diets, physical activity, and resources to reduce alcohol consumption and smoking. Further research is required to clarify their relationship and the underlying mechanisms.

Association between fatty acids and female infertility: dual evidence from a cross-sectional study and Mendelian randomization analysis

Background: Infertility poses a considerable threat to female reproductive health on a global scale. Dietary pattern, as a modifiable lifestyle factor, is frequently recommended as an important intervention for infertility-related diseases. Fatty acids play a crucial role in maintaining the health of the female reproductive system. However, the available evidence on the specific relationship between various types of fatty acids and infertility remains insufficient and controversial. Methods: Initially, a cross-sectional study was conducted utilizing the National Health and Nutrition Examination Survey (NHANES) database to collect data from women aged 18-45 years who met the inclusion criteria across the 2013-2020 cycles. Infertility was defined based on information gleaned from reproductive questionnaires. Fatty acid intake was determined by analyzing two 24 hour dietary recall interviews. Weighted logistic regression and weighted restricted cubic spline (RCS) analyses, incorporating covariate adjustments, were employed to preliminarily delineate the association between various types of fatty acids and proportions of fatty acid intake and female infertility risk. Model performance evaluation was carried out through receiver operating characteristic (ROC) curve analysis, complemented by the utilization of a nomogram diagram to gauge the infertility risk attributed to covariates. Genetic instrumental variables pertinent to diverse fatty acid profiles and female infertility were sourced from genome-wide association studies (GWAS). Mendelian randomization (MR), multivariable MR (MVMR) and reverse MR analyses were subsequently used to ascertain causality and reverse causality between distinct fatty acids and infertility, concurrently assessing for heterogeneity and horizontal pleiotropy. Results: In our NHANES analysis, a total of 3159 women were enrolled in the study, with a self-reported infertility prevalence of 11.49%. Infertile women exhibited significantly elevated intake of total omega-6 and omega-6/total fatty acids (TFA) compared to the controls. Weighted logistic regression models confirmed positive correlations between total omega-6 (continuous) and omega-6/TFA (categorical) and infertility risk, while omega-3 (continuous) intake demonstrated a negative correlation. Model 2, post rigorous multivariate covariate adjustment, showed improved predictive performance according to ROC curve analysis. Subgroup analysis suggested that the positive correlation between omega-6/TFA (continuous) and female infertility risk was not affected by stratification. Total omega-6 (continuous) emerged as a risk factor for infertile women aged 18-34 years. However, total saturated fatty acids (TSFAs, continuous), total omega-3 (continuous) and total polyunsaturated fatty acids (PUFAs, categorical) were protective factors only in the infertile women with a BMI ≥ 25 kg m-2. The positive associations between total omega-6 (Q4) and omega-6/TFA (continuous and Q3-Q4) and infertility risk were consistent across all BMI subgroups. MR analysis employing inverse variance weighted (IVW) as the primary method and Bonferroni correction revealed that genetically predicted TSFAs, monounsaturated fatty acids (MUFAs), omega-6 and MUFA/TFA were positively associated with female infertility risk, whereas PUFA/TFA showed a negative association. Importantly, the positive associations between MUFAs and omega-6 and infertility risk remained robust even after adjusting for potential confounders using MVMR analyses. Reverse MR analysis did not provide any evidence for reverse causality. The MR-Egger regression intercept and Cochran's Q test did not detect any heterogeneity or horizontal pleiotropy. Conclusions: This study presents compelling evidence to substantiate the link between diverse fatty acids, particularly omega-6 PUFAs, and the risk of female infertility. However, to fully comprehend the potential mechanisms and impact of distinct fatty acids and their compositional ratios on female infertility, extensive future research spanning fundamental and large-scale clinical inquiries is imperative.

Higher oxidative balance score is associated with lower female infertility: a cross-sectional study

Background

An imbalance of the pro-oxidant and antioxidant profiles in the body contributes to the development of diseases, including female infertility.

Methods

In this study, we performed a secondary analysis of the National Health and Nutrition Examination Survey and calculated the values of oxidative balance score (OBS). A weighted logistic regression model was used to explore the potential relationship between OBS (continuous factor and quartile set) and female infertility, and the P for trend was calculated. Subgroup analyses were also carried out further to explore the association between OBS and female infertility, and the P for interactions were obtained.

Results

There were 1,626 females (aged 18 to 45) included in the study, including 198 with infertility and a prevalence of approximately 13.28%. Multifactorial logistic regression showed a 5% decrease in infertility for each unit increased in OBS (OR, 0.95; 95% CI, 0.92 to 0.98). When OBS was used as a categorical variable, female infertility decreased by 60% in the highest OBS group compared with the lowest OBS group (OR, 0.40; 95% CI, 0.21 to 0.74). In addition, subgroup analyses showed that the negative association between OBS and infertility was significant in the non-chronic disease (hypertension and diabetes) population, those with less than a high school educational background, poverty-to-income ratio (1 to 3), and those with more than 30 years of age.

Conclusion

Higher OBS was negatively associated with female infertility. Further prospective studies are needed to determine causality and to provide new perspectives on female infertility in the context of diet and lifestyle.