Impaired glucose tolerance and cardiovascular risk factors in relation to infertility: a Mendelian randomization analysis in the Norwegian Mother, Father, and Child Cohort Study

Association between Life's Essential 8 and Infertility as Well as the Mediating Effects of Oxidative Stress and Inflammatory Factors Among U.S. Women Aged 18-45 Years

Management of cardiovascular disease in pregnancy is important, yet the association between cardiovascular health and infertility is rarely reported. In this study, we aimed to explore the association between Life's Essential 8 (LE8), a novel cardiovascular health (CVH) measure, and infertility, and to investigate potential mediating mechanisms. This study investigated cross-sectional data from the 2013-2018 National Health and Nutrition Examination Survey. LE8 score (ranging from 0 to 100) was calculated as the unweighted average of eight CVH metrics. The association between LE8 and infertility was explored through weighted multiple logistic regression. Restricted cubic splines were used to explore nonlinear correlation. In addition, mediation analysis was conducted to investigate the role of oxidative stress and inflammatory markers systematically. After strict exclusion criteria, 1703 American women aged 18-45 years were included. After full adjustment, the LE8 score showed a negative correlation with infertility [per 1 SD increase, OR = 0.675, 95% CI: 0.553-0.824], with a linear dose-response relationship (non-linear P = 0.122). Similar linear negative correlations were found between health factor scores and infertility, with higher body mass index and glucose scores having a significantly lower risk of infertility. Stratified analyses showed a stronger inversed relationship between LE8 and infertility in younger populations. Moreover, mediation analysis revealed that uric acid concentration and lymphocyte count mediated the effect of LE8 on infertility (P < 0.05). LE8 and its subscale scores were linearly and negatively associated with infertility, which may be mediated in part through uric acid and lymphocyte count. Focusing on weight management and glycemic control can effectively reduce the risk of infertility.

Vascular Health of Females with History of Assisted Reproductive Technology

The use of assisted reproductive technologies (ART) for the treatment of infertility is gaining popularity. Limited data on the overall vascular health of females with history of ART are available. This pilot study aimed to investigate the overall vascular health of females with history of ART compared to individuals who conceived spontaneously. The assessment of overall vascular health included the measurement of brachial blood pressure, central blood pressure, and pulse wave velocity, as well as the evaluation of the arterial stiffness and carotid intima-media thickness (cIMT) of the common carotid arteries. Conventional blood lipids including lipoprotein a (Lp(a)) were also determined. In total, 45 females with history of ART and 52 females who conceived spontaneously were included (mean age: 47.72 ± 5.96 years vs. 46.84 ± 7.43 years, p = 0.525). An initial comparison revealed a significantly higher prevalence of elevated Lp(a) in ART females (p = 0.011). However, after multiple comparison correction, the significant result disappeared (p = 0.132). Within the cohort of ART females, no significantly higher cardiovascular risk was detected regarding vascular function. The potentially higher prevalence of elevated Lp(a) in ART females must be further investigated in future studies, as it might contribute to the impaired reproductive process in this cohort.

The association of Life's Simple 7 and infertility among U.S. women

Background

The Life's Simple 7 (LS7) metric is a comprehensive measure of cardiovascular health (CVH) that encompasses seven distinct risk factors and behaviors associated with cardiovascular disease (CVD). Some studies have shown an association between infertility and CVD. The present study aimed to explore the potential association between the LS7 factors and infertility.

Methods

A cross-sectional study was conducted on a sample of 3537 women aged 18-44 years from the National Health and Nutrition Examination Survey (NHANES) spanning the years 2013-2018. The LS7 metrics encompassed various factors including physical activity, smoking habits, body mass index, blood pressure levels, dietary patterns, blood glucose levels, and total cholesterol levels. We computed a 14-point LS7 score based on participants' baseline data, classifying them as "inadequate" (3-6), "average" (7-10), or "ideal" (11-14). Infertility is defined as an affirmative answer to either of two questions on the NHANES questionnaire: "Have you tried to conceive for at least one year without success?" and "Have you sought medical help for your inability to conceive?" Logistic regression was utilized to estimate odds ratios (O.R.s) and 95% confidence intervals (C.I.s).

Results

In total, 17.66% of participants were classified as individuals who reported experiencing infertility. In the continuous analysis, each one-unit increase in LS7 score was associated with a significantly decreased odds of infertility (OR=0.88 [0.77-0.89]). Analyzing the categorical representation of LS7 score, compared to individuals with poor scores, those with ideal scores exhibited a substantial 58% reduction in the odds of infertility (OR=0.42 [0.26-0.69]). Additionally, the observed interaction suggested that the influence of age on the relationship between LS7 and infertility is not consistent across different age groups (P for interaction < 0.001). Among individuals aged 35 or younger, each unit increase in LS7 score was associated with a substantial 18% (OR=0.82 [0.76-0.89]) decrease in the odds of infertility. However, in the older age group (>35), the association was attenuated and non-significant.

Conclusions

Our research suggests a significant inverse association between LS7 scores and infertility. Age demonstrated a varying impact on this relationship, with a more pronounced impact observed among individuals aged 35 or younger.