Infertility, recurrent pregnancy loss, and risk of stroke: pooled analysis of individual patient data of 618 851 women

Causal associations of male infertility with stroke: a two-sample Mendelian randomization study

Background

Stroke is a devastating global health issue, with high mortality and disability rates. The increasing prevalence of male infertility among reproductive-aged men has become a growing concern worldwide. However, the relationship between male infertility and stroke incidence remains uncertain. This study aimed to address this knowledge gap by employing a Mendelian randomization (MR) approach.

Method

Utilizing genetic instrumental variables derived from a genome-wide association study (GWAS) on male infertility and stroke, a two-sample MR design was implemented. Five different analysis methods, with inverse-variance weighted as the primary approach, were used to examine the genetic causal associations between male infertility and various stroke subtypes. Heterogeneity analysis, pleiotropy tests, and leave-one-out validation were conducted to assess heterogeneity, evaluate pleiotropy, and ensure the robustness of the findings.

Result

The results indicate a potential lower risk of small vessel stroke associated with male infertility (odds ratio, 95% confidence interval: 0.82, 0.68 to 0.99, p=0.044), although no significant impact on other stroke subtypes was observed. The study exhibited low heterogeneity and no apparent pleiotropy; however, the stability of the results was not optimal.

Conclusion

Male infertility might potentially confer a protective effect against small vessel stroke risk. Caution is warranted due to potential confounding factors. Additional studies are necessary to confirm these findings and provide further validation.

Metabolic disorders mediate the relation of miscarriage with cardiovascular diseases

AIMS

The extent to which the contribution of pregnancy loss to cardiovascular diseases (CVDs) can be explained by metabolic disorders is poorly elucidated but holds insights for reducing long-term cardiovascular risk. The aim of this study is to investigate the mediating effects of hypertension, diabetes mellitus (DM), and lipoprotein metabolism disorders on the association of miscarriage and stillbirth with coronary heart disease (CHD), stroke, heart failure, atrial fibrillation, and composite outcomes.

METHODS AND RESULTS

A total of 163 283 ever-gravid women (age 55.3 ± 7.9 years) from the UK Biobank cohort without established metabolic disorders and CVDs were included and followed from 2007 to 2010 baseline until December 2020. Causal mediation analyses were used to estimate the proportion mediated. Hypertension mediated 11.1% (95% confidence interval, 3.7-18.5%) of the association between a history of miscarriage and incident CHD. Approximately, 9.5% (4.1-14.8%) of the effect of recurrent miscarriages on incident CHD was via hypertension, 8.4% (2.5-14.3%) of the effect was via lipoprotein metabolism disorders, 1.7% (0.5-2.9%) of the effect was via DM, and 10.7% (0.2-21.1%) of the effect of recurrent miscarriages on incident stroke was via hypertension. Hypertension mediated the largest proportion of effect for the atherosclerotic cardiovascular event (15.5% for a history of miscarriage and 9.4% for recurrent miscarriages), followed by lipoprotein metabolism disorders and DM.

CONCLUSION

Hypertension, DM, and lipoprotein metabolism disorders mediated the association between miscarriage and various cardiovascular outcomes in later life. In particular, hypertension mediated a large proportion of the relationship between miscarriage and atherosclerotic CVD.

History of Infertility and Midlife Cardiovascular Health in Female Individuals

Importance

Fertility status is a marker for future health, and infertility has been associated with risk for later cancer and diabetes, but associations with midlife cardiovascular health (CVH) in female individuals remain understudied.

Objective

To evaluate the association of infertility history with CVH at midlife (approximately age 50 years) among parous individuals.

Design, Setting, and Participants

Project Viva is a prospective cohort study of pregnant participants enrolled between 1999 and 2002 who delivered a singleton live birth in the greater Boston, Massachusetts, area. Infertility history was collected at a midlife visit between 2017 and 2021, approximately 18 years after enrollment. Data analysis was performed from January to June 2023.

Exposures

The primary exposure was any lifetime history of infertility identified by self-report, medical record, diagnosis, or claims for infertility treatment.

Main Outcomes and Measures

The American Heart Association's Life's Essential 8 (LE8) is a construct for ranking CVH that includes scores from 0 to 100 (higher scores denote better health status) in 4 behavioral (diet, physical activity, sleep, and smoking status) and 4 biomedical (body mass index, blood pressure, blood lipids, and glycemia) domains to form an overall assessment of CVH. Associations of a history of infertility (yes or no) with mean LE8 total, behavioral, biomedical, and blood biomarker (lipids and glycemia) scores were examined, adjusting for age at outcome (midlife visit), race and ethnicity, education, household income, age at menarche, and perceived body size at age 10 years.

Results

Of 468 included participants (mean [SD] age at the midlife visit, 50.6 [5.3] years) with exposure and outcome data, 160 (34.2%) experienced any infertility. Mean (SD) LE8 scores were 76.3 (12.2) overall, 76.5 (13.4) for the behavioral domain, 76.0 (17.5) for the biomedical domain, and 78.9 (19.2) for the blood biomarkers subdomain. In adjusted models, the estimated overall LE8 score at midlife was 2.94 points lower (95% CI, -5.13 to -0.74 points), the biomedical score was 4.07 points lower (95% CI, -7.33 to -0.78 points), and the blood subdomain score was 5.98 points lower (95% CI, -9.71 to -2.26 points) among those with vs without history of infertility. The point estimate also was lower for the behavioral domain score (β = -1.81; 95% CI, -4.28 to 0.66), although the result was not statistically significant.

Conclusions and Relevance

This cohort study of parous individuals found evidence for an association between a history of infertility and lower overall and biomedical CVH scores. Future study of enhanced cardiovascular preventive strategies among those who experience infertility is warranted.

Impact of adverse pregnancy outcomes on brain vascular health and cognition

A State of the Art lecture titled "Impact of Adverse Pregnancy Outcomes on Brain Vascular Health and Cognition" was presented at the International Society on Thrombosis and Haemostasis Congress in 2023. Adverse pregnancy outcomes, encompassing conditions such as gestational hypertension, eclampsia, preeclampsia, preterm birth, fetal growth restriction, stillbirth, and gestational diabetes, may form part of an underrecognized pathway from early adulthood reproductive health factors to later-life vascular cognitive impairment and dementia in women. Adverse pregnancy outcomes are caused by dysregulated vascular and metabolic adaptations during pregnancy, and these pathophysiological changes may persist after delivery. Adverse pregnancy outcomes may contribute to the increased risk of cognitive impairment and dementia directly through vascular and metabolic dysregulation and subsequent development of cardiovascular diseases, or other biological processes may be at play, such as shared maternal risk factors. Extensive epidemiologic evidence has shown that many cognitive impairment and dementia cases may be prevented or delayed by strategies targeting midlife cardiovascular health. Despite the recognized importance of adverse pregnancy outcomes for cardiovascular health, the literature on associated long-term health outcomes is limited. In this State of the Art review article, we summarize the current epidemiologic evidence on the relationship between adverse pregnancy outcomes and cognitive impairment and dementia and provide an overview of the potential pathophysiological mechanisms. Finally, we summarize relevant new data on this topic presented during the 2023 International Society on Thrombosis and Haemostasis Congress.

Incidence and influencing factors of fertility concerns in breast cancer in young women: a systematic review and meta-analysis

Objective

This systematic review and meta-analysis aimed to evaluate the prevalence and influencing factors of fertility concerns in breast cancer in young women.

Methods

A literature search on PubMed, Embase, Web of Science, and Cochrane Library databases was conducted up to February 2023 and was analyzed (Revman 5.4 software) in this study. The papers were chosen based on inclusion standards, and two researchers independently extracted the data. The included studies' quality was evaluated using criteria set out by the Agency for Healthcare Research and Quality. To identify significant variations among the risk factors, odds ratios (ORs) and the corresponding 95% confidence intervals (CIs) were utilized.

Results

A total of 7 studies that included 1579 breast cancer in young women were enrolled in the study. The results showed that for breast cancer in young women, the incidence of fertility concerns 53%(95%CI [0.45,0.58]). The results showed that education (2.65, 95% CI 1.65-5.63), full-time work (0.12, 95% CI 1.03-1.93), fertility intentions (7.84, 95% CI 1.50-37.4), depression level (1.25, 95% CI 1.03-1.5), and endocrine therapy (1.32, 95% CI 1.08-1.62) were risk factors for fertility concerns in young women with BC. Having a partner (0.41, 95% CI 0.33-0.5), ≥1 child (0.3, 95% CI 0.22-0.4) were identified as protective factors against fertility concerns in young women with BC.

Conclusions

The incidence of fertility concerns in breast cancer in young women is at a moderately high level. We should pay more attention to the risk factors of fertility concerns to help breast cancer in young women cope with their fertility concerns and promote their psychological well-being.

Polycystic Ovary Syndrome Fuels Cardiovascular Inflammation and Aggravates Ischemic Cardiac Injury

BACKGROUND

Reducing cardiovascular disease burden among women remains challenging. Epidemiologic studies have indicated that polycystic ovary syndrome (PCOS), the most common endocrine disease in women of reproductive age, is associated with an increased prevalence and extent of coronary artery disease. However, the mechanism through which PCOS affects cardiac health in women remains unclear.

METHODS

Prenatal anti-Müllerian hormone treatment or peripubertal letrozole infusion was used to establish mouse models of PCOS. RNA sequencing was performed to determine global transcriptomic changes in the hearts of PCOS mice. Flow cytometry and immunofluorescence staining were performed to detect myocardial macrophage accumulation in multiple PCOS models. Parabiosis models, cell-tracking experiments, and in vivo gene silencing approaches were used to explore the mechanisms underlying increased macrophage infiltration in PCOS mouse hearts. Permanent coronary ligation was performed to establish myocardial infarction (MI). Histologic analysis and small-animal imaging modalities (eg, magnetic resonance imaging and echocardiography) were performed to evaluate the effects of PCOS on injury after MI. Women with PCOS and control participants (n=200) were recruited to confirm findings observed in animal models.

RESULTS

Transcriptomic profiling and immunostaining revealed that hearts from PCOS mice were characterized by increased macrophage accumulation. Parabiosis studies revealed that monocyte-derived macrophages were significantly increased in the hearts of PCOS mice because of enhanced circulating Ly6C+ monocyte supply. Compared with control mice, PCOS mice showed a significant increase in splenic Ly6C+ monocyte output, associated with elevated hematopoietic progenitors in the spleen and sympathetic tone. Plasma norepinephrine (a sympathetic neurotransmitter) levels and spleen size were consistently increased in women with PCOS when compared with those in control participants, and norepinephrine levels were significantly correlated with circulating CD14++CD16- monocyte counts. Compared with animals without PCOS, PCOS animals showed significantly exacerbated atherosclerotic plaque development and post-MI cardiac remodeling. Conditional Vcam1 silencing in PCOS mice significantly suppressed cardiac inflammation and improved cardiac injury after MI.

CONCLUSIONS

Our data documented previously unrecognized mechanisms through which PCOS could affect cardiovascular health in women. PCOS may promote myocardial macrophage accumulation and post-MI cardiac remodeling because of augmented splenic myelopoiesis.

Mendelian randomization and colocalization analyses reveal an association between short sleep duration or morning chronotype and altered leukocyte telomere length

Observational studies suggest certain sleep traits are associated with telomere length, but the causal nature of these associations is unclear. The study aimed to determine the causal associations between 11 sleep-related traits and leukocyte telomere length (LTL) through two-sample Mendelian randomization and colocalization analyses using the summary statistics from large-scale genome-wide association studies. Univariable Mendelian randomization indicates that genetically determined short sleep is associated with decreased LTL, while morning chronotype is associated with increased LTL. Multivariable Mendelian randomization further supports the findings and colocalization analysis identifies shared common genetic variants for these two associations. No genetic evidence is observed for associations between other sleep-related traits and LTL. Sensitivity MR methods, reverse MR and re-running MR after removing potential pleiotropic genetic variants enhance the robustness of the results. These findings indicate that prioritizing morning chronotype and avoiding short sleep is beneficial for attenuating telomere attrition. Consequently, addressing sleep duration and chronotype could serve as practical intervention strategies.

Association of infertility with type and timing of menopause: a prospective cohort study

STUDY QUESTION

What is the association between past infertility and the type and timing of menopause in midlife women?

SUMMARY ANSWER

Women with a history of infertility were more likely to experience surgical menopause overall and had elevated risk of earlier surgical menopause until age 43 years but experienced no differences in the timing of natural menopause.

WHAT IS KNOWN ALREADY

Infertility is experienced by 12-25% of women and is thought to reveal a propensity for poor health outcomes, such as chronic illness, later in life. However, little is known about whether infertility is linked with characteristics of the menopausal transition as women age, despite possible shared underlying pathways involving ovarian function and gynecologic disease.

STUDY DESIGN, SIZE, DURATION

Secondary analysis of a prospective cohort study of 13 243 midlife females recruited in Phase 1 of the Alberta's Tomorrow Project (Alberta, Canada) and followed approximately every 4 years (2000-2022).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Data were collected through standardized self-report questionnaires. History of infertility, defined as ever trying to become pregnant for more than 1 year without conceiving, was measured at baseline. Menopause characteristics were measured at each study follow-up. Menopause type was defined as premenopause, natural menopause, surgical menopause (bilateral oophorectomy), or indeterminate menopause (premenopausal hysterectomy with ovarian conservation). Timing of natural menopause was defined as the age at 1 full year after the final menstrual period, and timing of surgical and indeterminate menopause was defined as the age at the time of surgery. We used flexible parametric survival analysis for the outcome of menopause timing with age as the underlying time scale and multinomial logistic regression for the outcome of menopause type. Multivariable models controlled for race/ethnicity, education, parity, previous pregnancy loss, and smoking. Sensitivity analyses additionally accounted for birth history, menopausal hormone therapy, body mass index, chronic medical conditions, and age at baseline.

MAIN RESULTS AND THE ROLE OF CHANCE

Overall, 18.2% of women reported a history of infertility. Past infertility was associated with earlier timing of surgical menopause exclusively before age 43 years (age 35: adjusted hazard ratio 3.13, 95% CI 1.95-5.02; age 40: adjusted hazard ratio 1.83, 95% CI 1.40-2.40; age 45: adjusted hazard ratio 1.13, 95% CI 0.87-1.46) as well as greater odds of experiencing surgical menopause compared to natural menopause (adjusted odds ratio 1.40, 95% CI 1.18-1.66). Infertility was not associated with the timing of natural or indeterminate menopause.

LIMITATIONS, REASONS FOR CAUTION

Information on the underlying cause of infertility and related interventions was not collected, which precluded us from disentangling whether associations differed by infertility cause and treatment. Residual confounding is possible given that some covariates were measured at baseline and may not have temporally preceded infertility.

WIDER IMPLICATIONS OF THE FINDINGS

Women with a history of infertility were more likely to experience early surgical menopause and may therefore benefit from preemptive screening and treatment for gynecologic diseases to reduce bilateral oophorectomy, where clinically appropriate, and its associated health risks in midlife. Moreover, the lack of association between infertility and timing of natural menopause adds to the emerging knowledge that diminishing ovarian reserve does not appear to be a primary biological mechanism of infertility nor its downstream implications for women's health.

STUDY FUNDING/COMPETING INTEREST(S)

Alberta's Tomorrow Project is only possible due to the commitment of its research participants, its staff and its funders: Alberta Health, Alberta Cancer Foundation, Canadian Partnership Against Cancer and Health Canada, and substantial in-kind funding from Alberta Health Services. The views expressed herein represent the views of the author(s) and not of Alberta's Tomorrow Project or any of its funders. This secondary analysis is funded by Project Grant Priority Funding in Women's Health Research from the Canadian Institutes of Health Research (Grant no. 491439). N.V.S. is supported by a Banting Postdoctoral Fellowship from the Canadian Institutes of Health Research. H.K.B. is supported by the Canada Research Chairs Program. E.A.B. is supported by an Early Career Investigator Award in Maternal, Reproductive, Child and Youth Health from the Canadian Institutes of Health Research. A.K.S. has received honoraria from Pfizer, Lupin, Bio-Syent, and Eisai and has received grant funding from Pfizer. N.V.S., H.K.B., and E.A.B. have no conflicts of interest to report.

TRIAL REGISTRATION NUMBER

N/A.

Is There a Relationship between Adverse Pregnancy Outcomes and Future Development of Atherosclerosis?

Cardiovascular disease is one of the main death causes globally. Effective cardiovascular risk management requires a thorough understanding of the mechanisms underlying the disorder. Establishing early markers of the disease allows a timely intervention and prevention of further atherosclerosis development. Multiple studies confirm the correlation between pregnancy disorders and cardiovascular disease in the postpartum period. Moreover, over 30% of women experience adverse pregnancy outcomes. Thus, the examination of the links between these conditions and atherosclerotic cardiovascular disease may help to identify gender-specific risk factors. In this review, we will explore the association between several adverse pregnancy outcome conditions and atherosclerosis. The current analysis is based on the data from several recent studies on the mechanisms behind gestational diabetes, hypertensive disorders of pregnancy, miscarriages, and stillbirths and their implications for the female cardiovascular system.

Risk of Stroke Hospitalization After Infertility Treatment

Importance

Stroke accounts for 7% of pregnancy-related deaths in the US. As the use of infertility treatment is increasing, many studies have sought to characterize the association of infertility treatment with the risk of stroke with mixed results.

Objective

To evaluate the risk of hospitalization from hemorrhagic and ischemic strokes in patients who underwent infertility treatment.

Design, Setting, and Participants

This population-based, retrospective cohort study used data abstracted from the Nationwide Readmissions Database, which stores data from all-payer hospital inpatient stays from 28 states across the US, from 2010 and 2018. Eligible participants included individuals aged 15 to 54 who had a hospital delivery from January to November in a given calendar year, and any subsequent hospitalizations from January to December in the same calendar year of delivery during the study period. Statistical analysis was performed between November 2022 and April 2023.

Exposure

Hospital delivery after infertility treatment (ie, intrauterine insemination, assisted reproductive technology, fertility preservation procedures, or use of a gestational carrier) or after spontaneous conception.

Main Outcomes and Measures

The primary outcome was hospitalization for nonfatal stroke (either ischemic or hemorrhagic stroke) within the first calendar year after delivery. Secondary outcomes included risk of stroke hospitalization at less than 30 days, less than 60 days, less than 90 days, and less than 180 days post partum. Cox proportional hazards regression models were used to estimate associations, which were expressed as hazard ratios (HRs), adjusted for confounders. Effect size estimates were corrected for biases due to exposure misclassification, selection, and unmeasured confounding through a probabilistic bias analysis.

Results

Of 31 339 991 patients, 287 813 (0.9%; median [IQR] age, 32.1 [28.5-35.8] years) underwent infertility treatment and 31 052 178 (99.1%; median [IQR] age, 27.7 [23.1-32.0] years) delivered after spontaneous conception. The rate of stroke hospitalization within 12 months of delivery was 37 hospitalizations per 100 000 people (105 patients) among those who received infertility treatment and 29 hospitalizations per 100 000 people (9027 patients) among those who delivered after spontaneous conception (rate difference, 8 hospitalizations per 100 000 people; 95% CI, -6 to 21 hospitalizations per 100 000 people; HR, 1.66; 95% CI, 1.17 to 2.35). The risk of hospitalization for hemorrhagic stroke (adjusted HR, 2.02; 95% CI, 1.13 to 3.61) was greater than that for ischemic stroke (adjusted HR, 1.55; 95% CI, 1.01 to 2.39). The risk of stroke hospitalization increased as the time between delivery and hospitalization for stroke increased, particularly for hemorrhagic strokes. In general, these associations became larger for hemorrhagic stroke and smaller for ischemic stroke following correction for biases.

Conclusions and Relevance

In this cohort study, infertility treatment was associated with an increased risk of stroke-related hospitalization within 12 months of delivery; this risk was evident as early as 30 days after delivery. Timely follow-up in the immediate days post partum and continued long-term follow-up should be considered to mitigate stroke risk.

[Gender-sensitive medical approaches in cardiology]

Gender-sensitive medicine takes into account differences of men and women in various diseases with regard to the biological ("sex") as well as the sociocultural ("gender") dimension. This article highlights gender differences in cardiovascular disease and the different prevention strategies based on these differences.

Infertility and Risk of Cardiovascular Disease: A Prospective Cohort Study

Background Certain symptoms associated with infertility are associated with cardiovascular disease, including menstrual cycle irregularity, early menopause, and obesity; however, few studies have investigated the association between infertility and cardiovascular disease risk. Methods and Results Participants in the NHSII (Nurses' Health Study II) who reported infertility (12 months of trying to conceive without success, including women who subsequently conceived) or who were gravid, with no infertility were followed from 1989 until 2017 for development of incident, physician-diagnosed coronary heart disease (CHD) (myocardial infarction, coronary artery bypass grafting, angioplasty, stent) and stroke. Time-varying Cox proportional hazard models were used to calculate hazard ratios (HRs) and 95% CIs and were adjusted a priori for potential confounding variables. Among 103 729 participants, 27.6% reported having ever experienced infertility. Compared with gravid women who had not reported infertility, women with a history of infertility had greater risk of CHD (HR, 1.13 [95% CI, 1.01-1.26]) but not stroke (HR, 0.91 [95% CI, 0.77-1.07]). The association between history of infertility and CHD was strongest among women who reported infertility at an earlier age (HR for infertility first reported at ≤25 years, 1.26 [95% CI, 1.09-1.46]; HR at 26-30 years, 1.08 [95% CI, 0.93-1.25]; HR at >30 years, 0.91 [95% CI, 0.70-1.19]). When we investigated specific infertility diagnoses, elevated risk of CHD was observed among women whose infertility was attributed to an ovulatory disorder (HR, 1.28 [95% CI, 1.05-1.55]) or endometriosis (HR, 1.42 [95% CI, 1.09-1.85]). Conclusions Women with infertility may be at an increased risk of CHD. Risk differed by age at first infertility diagnosis and was restricted to ovulatory- and endometriosis-related infertility.

Insulin resistance in women with recurrent miscarriage: a systematic review and meta-analysis

PURPOSE

This review aimed to investigate the association of insulin resistance (IR) in women with recurrent pregnancy loss compared to women with normal pregnancy history.

METHODS

PubMed, EMBASE, the Web of Science and Google Scholar databases were accessed to collect published observational studies that compared IR of recurrent pregnancy loss women with healthy women until the 6^th of October 2022. Outcomes assessed in this review and meta-analysis included fasting blood glucose, fasting plasma insulin, homeostasis model assessment for IR, glucose to insulin ratio. Mean differences, odds ratios with 95% confidence interval were pooled using the fixed or random effect models. Sensitivity analyses were performed to validate the robustness of the results. Review Manager version 5.4.1 and Stata version 8.0 were used.

RESULTS

A total of nineteen studies involving 4453 individuals were included. Recurrent pregnancy loss patients presented significantly higher fasting blood glucose, fasting plasma insulin, homeostasis model assessment for IR, and lower glucose to insulin ratios. Additionally, recurrent pregnancy loss patients had higher rates of IR as defined by abnormal fasting plasma insulin, homeostasis model assessment for IR, and glucose to insulin ratio. Sensitivity analyses validated the robustness of the results.

CONCLUSION

In the current review, we show that recurrent pregnancy loss is associated with a higher degree of IR and highlight the importance of screening and treatment of IR.

Women's reproductive traits and ischemic stroke: a two-sample Mendelian randomization study

OBJECTIVE

We conducted a Mendelian randomization (MR) study to disentangle causal associations between women's reproductive behaviors and ischemic stroke (IS) and investigate the roles of two modifiable risk factors (body mass index (BMI) and educational attainment (EA)) in these associations.

METHODS

Using summary-level data from large-scale genome-wide association studies, we performed univariable MR to examine whether there is genetic evidence that women's reproductive traits are causally associated with IS and its subtypes. Multivariable MR and MR mediation analysis were used to investigate whether BMI and EA are common mechanisms or mediators for these associations. A set of sensitivity analyses were conducted to test valid MR assumptions.

RESULTS

We observed consistent and statistically significant associations across female and sex-combined analyses for earlier age at first birth (AFB) and age at first sexual intercourse (AFS) with a higher risk of IS and large-artery atherosclerotic stroke (LAS) risk in the primary analysis. The odds ratios of IS per 1 SD increase in genetically predicted early AFB and AFS were 0.93 (95% CI, 0.86-0.99; p = 0.046) and 0.83 (95% CI, 0.70-0.97, p = 0.020), respectively. Further analyses indicated that BMI played a shared role in AFS and IS/LAS while EA played a shared role in AFS/AFB and IS/LAS as well as a mediator in the path from AFS to IS/LAS.

INTERPRETATION

These findings may inform prevention strategies and interventions directed toward relative women's reproductive behaviors and IS. Future studies are warranted to explore other factors related to EA which are responsible for these causalities.