Age at menopause and duration of reproductive period in association with dementia and cognitive function: A systematic review and meta-analysis

Accelerated Ovarian Failure as a Unique Model to Study Peri-Menopause Influence on Alzheimer's Disease

Despite decades of extensive research efforts, efficacious therapies for Alzheimer's disease (AD) are lacking. The multi-factorial nature of AD neuropathology and symptomatology has taught us that a single therapeutic approach will most likely not fit all. Women constitute ~70% of the affected AD population, and pathology and rate of symptoms progression are 2-3 times higher in women than men. Epidemiological data suggest that menopausal estrogen loss may be causative of the more severe symptoms observed in AD women, however, results from clinical trials employing estrogen replacement therapy are inconsistent. AD pathological hallmarks-amyloid β (Aβ), neurofibrillary tangles (NFTs), and chronic gliosis-are laid down during a 20-year prodromal period before clinical symptoms appear, which coincides with the menopause transition (peri-menopause) in women (~45-54-years-old). Peri-menopause is marked by widely fluctuating estrogen levels resulting in periods of irregular hormone-receptor interactions. Recent studies showed that peri-menopausal women have increased indicators of AD phenotype (brain Aβ deposition and hypometabolism), and peri-menopausal women who used hormone replacement therapy (HRT) had a reduced AD risk. This suggests that neuroendocrine changes during peri-menopause may be a trigger that increases risk of AD in women. Studies on sex differences have been performed in several AD rodent models over the years. However, it has been challenging to study the menopause influence on AD due to lack of optimal models that mimic the human process. Recently, the rodent model of accelerated ovarian failure (AOF) was developed, which uniquely recapitulates human menopause, including a transitional peri-AOF period with irregular estrogen fluctuations and a post-AOF stage with low estrogen levels. This model has proven useful in hypertension and cognition studies with wild type animals. This review article will highlight the molecular mechanisms by which peri-menopause may influence the female brain vulnerability to AD and AD risk factors, such as hypertension and apolipoprotein E (APOE) genotype. Studies on these biological mechanisms together with the use of the AOF model have the potential to shed light on key molecular pathways underlying AD pathogenesis for the development of precision medicine approaches that take sex and hormonal status into account.

Surgical menopause in association with cognitive function and risk of dementia: A systematic review and meta-analysis

INTRODUCTION

Experimental and epidemiological studies suggest female sex hormones to have long-lasting neuroprotective and anti-ageing properties. Surgically-induced menopause leads to a premature cessation of exposure to female sex hormones and could thus impact late-life cognitive function. Yet, evidence remains controversial.

METHODS

We systematically reviewed literature for articles investigating the association of surgical menopause (defined as bilateral oophorectomy before the onset of menopause) with risk of dementia, cognitive performance, cognitive decline, and Alzheimer's disease neuropathological indices later in life. We evaluated study quality with the Newcastle-Ottawa scale and performed random-effects meta-analyses.

RESULTS

We identified 11 eligible studies (N = 18,867). Although surgical menopause at any age was not associated with risk of dementia (4 studies; HR: 1.16, 95%CI: 0.96-1.43), early surgical menopause (≤45 years of age) was associated with a statistically significantly higher risk (2 studies; HR: 1.70, 95%CI: 1.07-2.69). Surgical menopause at any age was associated with faster decline in verbal memory, semantic memory, and processing speed, whereas early surgical menopause was further associated with faster global cognitive decline. No heterogeneity was noted. Among women undergoing surgical menopause, a younger age at surgery was associated with faster decline in global cognition, semantic and episodic memory, worse performance in verbal fluency and executive function, and accumulation of Alzheimer's neuropathology.

CONCLUSIONS

Current evidence is limited, but suggests surgical menopause induced by bilateral oophorectomy at ≤45 years of age to be associated with higher risk of dementia and cognitive decline. Additional large-scale cohort studies are necessary to replicate these findings.

Reproductive history and risk of cognitive impairment in Japanese women

OBJECTIVE

While exposure to endogenous estrogen may be associated with better cognitive performance, it is still unclear whether it has an association with mild cognitive impairment (MCI) or dementia. The aim of this study was to clarify the effects of reproductive history, as a surrogate marker of exposure to endogenous estrogen, on the risk of cognitive impairment (MCI or dementia) in women.

STUDY DESIGN

A total of 747 women aged 40-59 years in the Saku area (Nagano Prefecture) were followed as part of the Japan Public Health Center-based Prospective (JPHC) Study, which started in 1990. Participants had undergone a mental health examination in 2014-2015.

MAIN OUTCOME MEASURES

We used multiple logistic regression to analyze the association between reproductive history, obtained at baseline and 10-year follow-up, with current cognitive impairment diagnosed by a trained psychiatrist, adjusting for various lifestyle factors.

RESULTS

Among 670 eligible women, current cognitive impairment was diagnosed in 227, 196 of whom had MCI and 31 dementia. A longer reproductive period had a significantly inverse association with cognitive impairment (P-trend = 0.032). In particular, women with a reproductive period ≥38 years compared with ≤33 years had a significantly lower risk of cognitive impairment (multivariable adjusted odds ratio=0.62, 95% confidence interval=0.40-0.96).

CONCLUSIONS

A longer reproductive period was associated with a lower risk of cognitive impairment, which suggests that a longer exposure to endogenous estrogen may have a protective effect against cognitive impairment.

Premature natural menopause and cognitive function among older women in Indonesia

We examine the association between premature natural menopause and cognitive function among older women in Indonesia. Data come from Indonesia Family Life Survey (IFLS) 2014 (N = 1,031 menopausal women). Multilevel ordered logistic regression was used to take into account unobserved factors in the women's communities, also considering a range of potential confounding factors including their reproductive histories, lifestyles, and sociodemographic characteristics. The findings show that premature natural menopause was significantly associated with lower cognitive function in later life (ß = -0.97, P< .01, CI -1.61-(-0.33)). The findings were robust against potential confounding factors including reproductive history, lifestyle, and sociodemographic characteristics.

Reproductive period and risk of dementia in a diverse cohort of health care members

OBJECTIVE

Women have >50% greater lifetime risk of dementia than men but the role of female-specific endocrine milieu is not well-understood. This study evaluates associations between indicators of estrogen exposure from women's reproductive period and dementia risk in a large diverse population.

METHODS

We evaluated 15,754 female members (29.9% nonwhite) of Kaiser Permanente with clinical examinations and health survey data from 1964 to 1973 and were members as of January 1, 1996. In midlife (mean age 51.1 years), women reported age at menarche and menopause and hysterectomy status. Reproductive span was calculated as menopause age minus menarche age. Dementia diagnoses were abstracted from January 1, 1996 to September 30, 2017 medical records (mean age at start of dementia follow-up 76.5 years). Cox proportional hazard models evaluated associations between aspects of reproductive span and dementia risk adjusting for demographics and life course health indicators.

RESULTS

Forty-two percent of women developed dementia. Compared to menarche at age 13.0 (mean menarche age), menarche at ≥16 was associated with 23% greater dementia risk (adjusted hazard ratio [HR] 1.23; 95% confidence interval [CI] 1.01-1.50) adjusting for demographics and life course health indicators. Natural menopause at age <47.4 (mean menopause age) was associated with 19% elevated dementia risk (HR 1.19; 95% CI 1.07-1.31). Reproductive spans <34.4 years (mean duration) were associated with 20% elevated dementia risk (HR 1.20; 95% CI 1.08-1.32). Hysterectomies were associated with 8% elevated dementia risk (HR 1.08; 95% CI 1.01-1.16).

CONCLUSION

In this large prospective cohort study, endocrine events signaling less estradiol exposure (i.e., later age at menarche, younger age at menopause, shorter reproductive span, and hysterectomies) were associated with elevated risk of dementia.

Aberrant Cerebral Activity in Early Postmenopausal Women: A Resting-State Functional Magnetic Resonance Imaging Study

Background: Early postmenopausal women frequently suffer from cognitive impairments and emotional disorders, such as lack of attention, poor memory, deficits in executive function and depression. However, the underlying mechanisms of these impairments remain unclear. Method: Forty-three early postmenopausal women and forty-four age-matched premenopausal controls underwent serum sex hormone analysis, neuropsychological testing and resting-state functional magnetic resonance imaging (rs-fMRI). Degree centrality (DC) analysis was performed to confirm the peak points of the functionally abnormal brain areas as the centers of the seeds. Subsequently, the functional connectivity (FC) between these abnormal seeds and other voxels across the whole brain was calculated. Finally, the sex hormone levels, neuroimaging indices and neuropsychological data were combined to detect potential correlations. Results: Compared with the premenopausal controls, the early postmenopausal women exhibited significantly higher serum follicle-stimulating hormone (FSH) levels, more severe climacteric and depressive symptoms, worse sleep quality and more extensive cognitive impairments. Concurrently, the neuroimaging results showed elevated DC values in the left amygdala (AMYG.L), reduced DC values in the left middle occipital gyrus (MOG.L) and right middle occipital gyrus (MOG.R). When we used the AMYG.L as the seed point, FC with the left insula (INS.L), bilateral prefrontal cortex (PFC) and right superior frontal gyrus (SFG.R) was increased; these regions are related to depressive states, poor sleep quality and decreased executive function. When bilateral MOG were used as the seed points, FC with left inferior parietal gyrus (IPG.L), this area closely associated with impaired memory, was decreased. Conclusion: These results illuminated the regional and network-level brain dysfunction in early postmenopausal women, which might provide information on the underlying mechanisms of the different cognitive impairments and emotional alterations observed in this group.

Sex Differences and the Influence of Sex Hormones on Cognition through Adulthood and the Aging Process

Hormones of the hypothalamic-pituitary-gonadal (HPG) axis that regulate reproductive function have multiple effects on the development, maintenance and function of the brain. Sex differences in cognitive functioning have been reported in both health and disease, which may be partly attributed to sex hormones. The aim of the current paper was to provide a theoretical review of how sex hormones influence cognitive functioning across the lifespan as well as provide an overview of the literature on sex differences and the role of sex hormones in cognitive decline, specifically in relation to Alzheimer’s disease (AD). A summary of current hormone and sex-based interventions for enhancing cognitive functioning and/or reducing the risk of Alzheimer’s disease is also provided.

Age at menopause and lifetime cognition: Findings from a British birth cohort study

OBJECTIVE

We investigated whether cognitive performance between ages 43 and 69 years was associated with timing of menopause, controlling for hormone replacement therapy, childhood cognitive ability, and sociobehavioral factors.

METHODS

We used data from 1,315 women participating in the Medical Research Council National Survey of Health and Development (a British birth cohort study) with known age at period cessation and up to 4 assessments of verbal memory (word-learning task) and processing speed (letter-cancellation task) at ages 43, 53, 60-64, and 69. We fitted multilevel models with linear and quadratic age terms, stratified by natural or surgical menopause, and adjusted for hormone replacement therapy, body mass index, smoking, occupational class, education, and childhood cognitive ability.

RESULTS

Verbal memory increased with later age at natural menopause (0.17 words per year, 95% confidence interval [CI]: 0.07-0.27, p = 0.001); an association remained, albeit attenuated, after full adjustment (0.09, 95% CI: 0.02-0.17, p = 0.013). Verbal memory also increased with later age at surgical menopause (0.16, 95% CI: 0.06-0.27, p = 0.002), but this association was fully attenuated after adjustment. Search speed was not associated with age at menopause.

CONCLUSION

Our findings suggest lifelong hormonal processes, not just short-term fluctuations during the menopause transition, may be associated with verbal memory, consistent with evidence from a variety of neurobiological studies; mechanisms are likely to involve estrogen receptor β function. Further follow-up is required to assess fully the clinical significance of these associations.

Cognitive status in the oldest old and centenarians: a condition crucial for quality of life methodologically difficult to assess

Human life expectancy and the number of the oldest old are rapidly increasing worldwide. Advanced age is the main risk factor for dementia, representing one of the major causes of disability/dependency among older people with a strong impact on their families/caregivers. Centenarians have reached the extreme limits of human life escaping or delaying the major age-related diseases. Thus, these extraordinary individuals embody the best model to answer the crucial question if cognitive decline and dementia are progressive and unavoidable occurrences of increasing age. Despite a growing amount of data underlines the importance of cognitive function for quality of life and survival in old age, studies on centenarians have paid more attention to their physical condition rather than the assessment of their actual cognitive abilities. Accordingly, this work aims to summarize available data on the prevalence of dementia in centenarians and to critically address topics which can have a relevant impact on the cognitive assessment/status of the oldest old: (i) lack of standardized tools for cognitive assessment; (ii) criteria and threshold to establish the presence of dementia; (iii) influence of birth cohort and education; (iv) role of depression or positive attitude towards life; (v) gender differences.