Female reproductive factors and the risk of dementia: a nationwide cohort study

Association of reproductive factors with dementia: A systematic review and dose-response meta-analyses of observational studies

BACKGROUND

Associations between endogenous estrogen exposure indicators and risk of subtypes of dementia have been unclear.

METHODS

Databases (PubMed, EMBASE and Web of Science) were searched electronically on 1st July and updated regularly until 12nd November 2021. Observational studies of English language were selected if reported an effect estimate [e.g., odds ratio (OR), rate ratio (RR) or hazard ratio (HR)] and 95% CI for the association between any exposure (age of menarche, age at menopause, reproductive period, estradiol level) and any endpoint variable [all-cause dementia, Alzheimer's disease (AD), vascular dementia (VD), cognitive impairment (CI)]. Random-effects models and dose-response meta-analyses were used to calculate estimates and to show the linear/nonlinear relationship. PROSPERO CRD42021274827.

FINDINGS

We included 22 studies (475 9764 women) in this analysis. We found no clear relationship between late menarche (≥14 vs <14 years) and dementia, CI in categorical meta-analysis compared to a J-shape relationship in dose-response meta-analyses. Later menopause (≥45 vs <45 years) was consistently associated with a lower risk of all-cause dementia (pooled RR: 0.87, 95%CI: 0.78-0.97, I²=56.0%), AD (0.67, 0.44-0.99, I²=78.3%), VD (0.87, 0.80-0.94) and CI (0.82, 0.71-0.94, I²=19.3%) in categorical meta-analysis, showing similar results in dose-response meta-analyses. An inverse relationship between longer reproductive duration (≥35 vs <35 years) and dementia was observed in dose-response meta-analysis. In addition, estradiol levels after menopause were inversely correlated with the risk of AD and CI.

INTERPRETATION

In this study, later menopause and longer reproductive period were associated with a lower risk of dementia, while the relationship for menarchal age was J-shaped. There was an inverse relationship between higher postmenopausal estrogen levels and risk of AD and CI. Longitudinal study are needed to further explore the association between life-time estrogen exposure and risk of subtypes of dementia.

FUNDING

Start-up Foundation for Scientific Research in Shandong University.

Cognitive health after menopause: Does menopausal hormone therapy affect it?

Dementia is a pandemic chronic non-communicable disease. 10 in 100 women above age 65 will be diagnosed with dementia, primarily Alzheimer's disease (AD). Apart from age and hereditary risk factors, there are multiple acquired risk and protective factors. So far, Menopausal Hormone Therapy (MHT) is not recommended as preventive measure. A systematic literature search on MHT and dementia risk and MHT and cognitive performance in demented women, respectively, was performed. Two recent meta-analyses identified 18 and 16 studies analyzing the impact of MHT on dementia/AD risk. Our systematic literature search identified eight additional original articles. The majority of studies found a risk reducing impact of MHT by 11-33%. However, results may vary depending on MHT type, age at initiation and study design. For example, the Women's Health Initiative Memory Study (WHIMS) reported an approximately 2-fold increased risk of dementia/Alzheimer's disease if MHT comprising conjugated equine estrogens and medroxyprogesterone acetate was initiated in predominantly comorbid postmenopausal women above age 65. In general, MHT displays a beneficial effect on several dementia risk factors and also augments some protective factors. Accordingly, clinicians can be reassured that MHT can be safely prescribed in the context of cognition in women free of dementia. However, MHT is not indicated for cognitive improvement in demented women. International scientific guidelines on MHT and dementia should consider incorporating most recent data.

The effect of hormone replacement therapy on cognitive function in healthy postmenopausal women: a meta-analysis of 23 randomized controlled trials

To investigate how hormone replacement therapy (HRT) intervention affects cognitive function in randomized controlled trials of healthy postmenopausal women, the PubMed and Web of Science databases were searched for relevant publications up to 1 May 2020. Random-effects, subgroup analysis, sensitivity analysis and meta-regression analyses were conducted with 23 selected publications. HRT had a significant negative effect on global cognition (standardized mean difference (SMD): -0.04, 95% confidence interval (CI): -0.08 to -0.01). Via subgroup analysis, for those older than 60 years and with more than 6 months' intervention duration, HRT aggravated global cognition (SMD: -0.05, 95% CI: -0.08 to -0.01; SMD: -0.05, 95% CI: -0.08 to -0.01). The results of meta-regression demonstrated no significant association between HRT intervention and global cognition after adjusting for participants' age or intervention duration. In conclusion, HRT had a significant negative effect on global cognition, and this effect might be especially more visible for those aged more than 60 years and with more than 6 months' intervention. Further randomized controlled trials for postmenopausal women with a younger age and short-term HRT exposure are necessary to clarify the effects of HRT on global and domain-specific cognitive functions.

The relationship between fertility history and incident dementia in the US Health and Retirement Study

OBJECTIVES

An emerging literature suggests that fertility history, which includes measures of parity and birth timing, may influence cognitive health in older ages, especially among women given their differential exposure to pregnancy and sex hormones. Yet, few studies have examined associations between measures of fertility history and incident dementia in population-based samples.

METHODS

We examined the associations between parity, younger age at first birth, and older age at last birth with incident dementia over a 16-year period in a prospective sample of 15,361 men and women aged 51-100 years at baseline drawn from the Health and Retirement Study. We used Cox regression and the Fine and Gray model to obtain cause-specific (csHRs) and subdistribution hazard ratios (sdHRs) for incident dementia from gender-stratified models in which we accounted for the semi-competing risk of death.

RESULTS

During the follow-up period (median 13.0 years), the crude incidence rate for dementia was 16.6 and 19.9 per 1,000 person-years for men and women, respectively. In crude models estimating csHRs, higher parity (vs. parity 2) and younger age at first birth were associated with increased risk of dementia for both genders. These associations did not persist after full covariate adjustment. Across all models in which we estimated sdHRs, we observed a positive relationship between older age at last birth and incident dementia for women only.

DISCUSSION

In this population-based, multi-ethnic cohort, we observed limited evidence for an association between measures of fertility history and incident dementia among men and women after adjusting for potential confounders.

FEMALE REPRODUCTIVE FACTORS AND THE RISK OF EXUDATIVE AGE-RELATED MACULAR DEGENERATION: A Nationwide Cohort Study

PURPOSE

To evaluate the association between female reproductive factors and the incidence of exudative age-related macular degeneration (AMD).

METHODS

A total of 1,297,388 postmenopausal women over 50 years of age who participated in both national health screening and cancer screening in 2009 were identified using the Korea National Health Insurance System database. Data on female reproductive factors were collected using a self-administered questionnaire. Patients were followed up until 2018, and the incident cases of exudative AMD were identified. The hazard ratios and 95% confidence intervals for exudative AMD were estimated using the multivariable-adjusted Cox proportional hazard model.

RESULTS

During a mean follow-up of 7.27 years, 4,086 patients were newly diagnosed with exudative AMD. The hazard ratio (95% confidence intervals) for exudative AMD was 1.14 (1.01-1.31) for a reproductive period ≥40 years compared with a reproductive period <30 years, 1.72 (1.48-2.00) for patients with ≥5 years of hormone replacement therapy, and 1.29 (1.09-1.52) for those with 2 to 5 years of hormone replacement therapy compared with those who never underwent hormone replacement therapy.

CONCLUSION

Female reproductive factors were associated with the risk of exudative AMD. Greater lifetime exposure to endogenous and exogenous estrogen was associated with a higher incidence of exudative AMD.

Menopause and cognitive impairment: A narrative review of current knowledge

A severe impairment of cognitive function characterizes dementia. Mild cognitive impairment represents a transition between normal cognition and dementia. The frequency of cognitive changes is higher in women than in men. Based on this fact, hormonal factors likely contribute to cognitive decline. In this sense, cognitive complaints are more common near menopause, a phase marked by a decrease in hormone levels, especially estrogen. Additionally, a tendency toward worsened cognitive performance has been reported in women during menopause. Vasomotor symptoms (hot flashes, sweating, and dizziness), vaginal dryness, irritability and forgetfulness are common and associated with a progressive decrease in ovarian function and a subsequent reduction in the serum estrogen concentration. Hormone therapy (HT), based on estrogen with or without progestogen, is the treatment of choice to relieve menopausal symptoms. The studies conducted to date have reported conflicting results regarding the effects of HT on cognition. This article reviews the main aspects of menopause and cognition, including the neuroprotective role of estrogen and the relationship between menopausal symptoms and cognitive function. We present and discuss the findings of the central observational and interventional studies on HT and cognition.

The role of age at menarche and age at menopause in Alzheimer's disease: evidence from a bidirectional mendelian randomization study

The association between endogenous estrogen exposure and Alzheimer's disease (AD) remains inconclusive in previous observational studies, and few Mendelian randomization (MR) studies have focused on their causality thus far. We performed a bidirectional MR study to clarify the causality and causal direction of age at menarche and age at menopause, which are indicators of endogenous estrogen exposure, on AD risk. We obtained all genetic datasets for the MR analyses using publicly available summary statistics based on individuals of European ancestry from the IEU GWAS database. The MR analyses indicated no significant causal relationship between the genetically determined age at menarche (outlier-adjusted inverse variance weighted odds ratio [IVWOR] = 0.926; 95% confidence interval [CI], 0.803-1.066) or age at menopause (outlier-adjusted IVWOR = 0.981; 95% CI, 0.941-1.022) and AD risk. Similarly, AD did not show any causal association with age at menarche or age at menopause. The sensitivity analyses yielded similar results. In contrast, an inverse association was detected between age at menarche and body mass index (BMI, outlier-adjusted IVW β = -0.043; 95% CI, -0.077 to -0.009). Our bidirectional MR study provides no evidence for a causal relationship between the genetically determined age at menarche or age at menopause and AD susceptibility, or vice versa. However, earlier menarche might be associated with higher adult BMI.

A Lifecourse Perspective on Female Sex-Specific Risk Factors for Later Life Cognition

PURPOSE OF REVIEW

The prevalence of Alzheimer's disease and related dementias is greater in women compared to men. We provide a review of female sex-specific risk factors across the lifecourse for cognition in older adulthood, highlighting areas that need further study.

RECENT FINDINGS

Pregnancy may affect late-life cognition, with adverse pregnancy outcomes associated with an increased risk of cognitive decline but parity providing a protective effect. Cumulative estrogen exposure, influenced by age of menarche, menopause, and exogenous estrogen use, may modify a woman's risk for dementia. Menopause transition-associated symptoms may impact cognitive health at the time of the symptoms, but long-term effects remain unknown. As compared to natural menopause, surgical menopause seems to increase the risk for cognitive impairment. Studies that have assessed the association between women's reproductive health and cognition have produced conflicting results. Future studies that address these inconsistencies among diverse populations are needed to better care for women throughout their lives.

Reproductive period and preclinical cerebrospinal fluid markers for Alzheimer disease: a 25-year study

OBJECTIVE

The aim of the study was to examine the association between reproductive period, as an indicator of endogenous estrogen, and levels of cerebrospinal fluid (CSF) biomarkers for Alzheimer disease (AD).

METHODS

A population-based sample of women from Gothenburg, Sweden was followed from 1968 to 1994 (N = 75). All women had natural menopause and were free from dementia. Information on reproductive period (age at menarche to age at menopause) was obtained from interviews from 1968 to 1980. Lumbar puncture was performed from 1992 to 1994 and CSF levels of Aβ42, Aβ40, P-tau, and T-tau were measured with immunochemical methods. Linear regression models adjusted for potential confounders were used to analyze the relationship between reproductive period and CSF biomarkers for AD.

RESULTS

Longer reproductive period was associated with lower levels of Aβ42 (β = -19.2, P  = 0.01), higher levels of P-tau (β = 0.03, P  = 0.01), and lower ratio of Aβ42/Aβ40 (β = -0.02, P  = 0.01), while no association was observed for T-tau (β = 0.01, P  = 0.46). In separate analyses, examining the different components of reproductive period, earlier age at menarche was associated higher levels of P-tau (β = -0.07, P  = 0.031) and lower ratio of Aβ42/Aβ40 (β = 0.05, P  = 0.021), whereas no association was observed with Aβ42 (β = 31.1, P  = 0.11) and T-tau (β = -0.001, P  = 0.98). Furthermore, no association was observed between age at menopause and CSF biomarkers for AD.

CONCLUSIONS

Our findings suggest that longer exposure to endogenous estrogen may be associated with increased levels of AD biomarkers in the preclinical phase of AD. These findings, however, need to be confirmed in larger samples.

Reproductive risk factors of pterygium in postmenopausal women: a nationwide study in the Republic of Korea

This study is to elucidate the associations between female reproductive factors and pterygium. A total of 1,339,969 postmenopausal women in a retrospective cohort of Korean National Health Insurance Service data on ages 40 and above in 2009 was included. Cox proportional hazards regression was conducted to assess the hazard ratio (HR) for pterygium according to reproductive factors. Late menarche, early menopause, short reproductive period, increasing parity (≥ 2 children), breastfeeding (≥ 6 months), and no use of hormone replacement therapy (HRT) or oral contraceptive (OC) were significantly associated with risk of pterygium. In multivariate analysis, the HR for pterygium was 1.764 (95% confidence interval [CI], 1.529–2.035) for menarche age ≥ 17 years (reference: menarche age < 12 years). The HR of menopause age ≥ 55 years was 0.782 (95% CI, 0.724–0.845) (reference: menopause age < 40 years). The HR of parity ≥ 2 was 1.261 (95% CI, 1.148–1.385) (reference: nulliparity). The HR of breastfeeding ≥ 1 year was 1.663 (95% CI, 1.564–1.768) (reference: no breastfeeding). The HRs of HRT and OC use for any length of time were lower than those for the non-user groups (reference). Reproductive factors that increase estrogen exposure have protective effects against pterygium in females.

The Treatment of Complementary and Alternative Medicine on Premature Ovarian Failure

It has been confirmed by growing evidence that common hormone replacement therapy is associated with an increasing risk of causing cardiovascular disease and cancer, while complementary and alternative medicine (CAM) is gaining popularity and application in more and more patients with premature ovarian failure (POF). Although there is little data concerning the clinical safety and efficacy of CAM, the literature includes application studies on the phytoestrogen-rich herbal, acupuncture treatment and intervention therapy. This article reviews recent literature on CAM therapy for POF, aiming to provide theoretical support for clinical application.