Effect of postmenopausal hormone therapy on cognitive function: the Heart and Estrogen/progestin Replacement Study

Estrogen and the brain: does estrogen treatment improve cognitive function?

In this paper we describe potential reasons for the discrepancies between data from basic sciences and observational studies and those of large treatment studies investigating the association between brain function and sex steroids. Observational studies which often showed positive associations between hormone use and cognition can be affected by 'recall bias' and 'healthy user bias', while outcomes of treatment studies were hypothesized to be modified by age at treatment, age at or type of menopause, health status, addition of a progestogen or type of estrogen treatment. However, meta-analyses of data from treatment studies negate many of these hypotheses showing at best mainly short-term (up to 6 months) positive effects of estrogen treatment on cognition regardless of age. This positive effect may reverse, particularly in older women with prolonged hormone treatment, which was predominantly seen after addition of progestogen. Medroxyprogesterone acetate seemed to have worse effects on cognition than other types of progestogen in these long-term studies. Estradiol with or without a progestogen was three times more likely to have positive effects on cognition than conjugated equine estrogens. However, two-thirds of studies showed no associations at all which may be an underestimate given the possibility of publication bias. We briefly review alternative treatments, such as testosterone and soy-derived supplements, but currently insufficient data are available for conclusive comments. Women who have undergone surgical menopause or who undergo natural menopause before age 47 may benefit most from hormone treatment and a special case may need to be made for this group. Long-term safety studies for this group are urgently needed.

Object recognition memory and temporal lobe activation after delayed estrogen replacement therapy

The critical window hypothesis predicts that estrogen replacement therapy (ERT) must be administered early on the menopause or ovariectomy (OVX) to positively affect cognition. However, the neural substrates, underling the time dependent efficacy of ERT, are still not completely known. In order to address this issue, we submitted female mice to 12 weeks of OVX followed by 5 weeks of chronic ERT (OVX(E2)). Within the first 12 weeks, the OVX animals showed a progressive compromised performance in the object recognition memory (ORM) task. After ERT, OVXE2 mice, but not the control group (OVXoil), were able to recognize the new object in the test session. Further, we evaluated the c-Fos expression in hippocampus, perirhinal cortex (PC) and central amygdala (CeA) of OVXoil and OVX(E2) mice, after context exposure (CTX) or object exploration (OBJ). We observed that ERT increased c-Fos expression unspecifically for CTX and OBJ. In addition, only the OVX(E2) group showed significantly higher c-Fos expression in the PC and CeA after object exploration. Thus, our results showed that delayed chronic ERT improves ORM (compromised by OVX) and increases constitutive c-Fos expression in temporal lobe regions. Furthermore, we showed for the first time that PC and CeA, but not the hippocampus, present a distinct pattern of activation in response to object exploration in ovariectomized females that underwent delayed-ERT.

Brain endogenous estrogen levels determine responses to estrogen replacement therapy via regulation of BACE1 and NEP in female Alzheimer's transgenic mice

Estrogens have been found to improve memory and reduce risk of dementia, although conflicting results such as failure of estrogen replacement therapy for treatment of Alzheimer's disease (AD) also has been reported. Only recently, our published human brain studies showed a depletion of brain estrogen in women with AD, while other studies have demonstrated cognitive impairment believed to be caused by inhibition of endogenous estrogen synthesis in females. To investigate whether the shortage of brain estrogen alters the sensitivity of response to estrogen replacement therapy, we have used genetic and surgical animal models to examine the response of estrogen treatment in AD neuropathology. Our studies have shown that early treatment with 17β-estradiol (E2) or genistein could reduce brain amyloid levels by increasing Aβ clearance in both APP23 mice with genetic deficiency of aromatase (APP/Ar(+/-)), in which the brains contain nondetectable levels of estrogen, and in APP23 mice with an ovariectomy (APP/OVX), in which the brains still contain certain levels of estrogen. However, only APP/Ar(+/-) mice showed a great reduction in brain amyloid plaque formation after E2 or genistein treatment along with downregulation of β-secretase (BACE1) mRNA and protein expression. Our results suggest that early and long-term usage of E2 and/or genistein may prevent AD pathologies in a dependent manner on endogenous brain estrogen levels in aged females.

Sex and gonadal hormones in mouse models of Alzheimer's disease: what is relevant to the human condition?

Biologic sex and gonadal hormones matter in human aging and diseases of aging such as Alzheimer's - and the importance of studying their influences relates directly to human health. The goal of this article is to review the literature to date on sex and hormones in mouse models of Alzheimer's disease (AD) with an exclusive focus on interpreting the relevance of findings to the human condition. To this end, we highlight advances in AD and in sex and hormone biology, discuss what these advances mean for merging the two fields, review the current mouse model literature, raise major unresolved questions, and offer a research framework that incorporates human reproductive aging for future studies aimed at translational discoveries in this important area. Unraveling human relevant pathways in sex and hormone-based biology may ultimately pave the way to novel and urgently needed treatments for AD and other neurodegenerative diseases.

Hormone-replacement therapy, dementia and stroke

Hormone-replacement therapy (HRT) has been used for more than 40 years to reduce perimenopausal symptoms. Estrogens may protect brain structures and functional systems affected by Alzheimer's disease, which suggests that maintaining high levels of hormones with HRT can protect against Alzheimer's disease. Moreover, high premenopausal estrogen concentrations are thought to be protective against stroke and, consequently, in the past, HRT was considered to be a potential protective agent against stroke. However, large clinical trials have failed to demonstrate a benefit from HRT on either cognitive performance or risk of dementia. In addition, although HRT has been associated with a reduction in the risk of heart disease in observational studies, results regarding stroke have been less clear. Recently, evidence has shown that HRT does not reduce but actually increases vascular risk. Here, the data from the most important studies are examined, concluding that HRT has no beneficial effect on dementia or stroke risk reduction in postmenopausal women.

Hormone therapy, dementia, and cognition: the Women's Health Initiative 10 years on

Principal findings on dementia from the Women's Health Initiative Memory Study (WHIMS) showed that conjugated equine estrogens plus medroxyprogesterone acetate (CEE/MPA) increase dementia risk in women aged 65 years and above, but not risk of mild cognitive impairment. The dementia finding was unexpected, given consistent observational evidence that associates use of estrogen-containing hormone therapy with reduced risk of Alzheimer's disease. It remains controversial whether hormone use by younger postmenopausal women near the time of menopause reduces dementia risk or whether WHIMS findings should be generalized to younger women. Given the challenges of conducting a primary prevention trial to address that question, it is helpful to consider the impact of hormone therapy on cognitive test performance, particularly verbal memory, for its own sake and as a proxy for dementia risk. The WHI Study of Cognitive Aging (WHISCA) showed that CEE/MPA worsened verbal memory, whereas CEE alone had no influence on cognition. These findings have been replicated in several randomized, clinical trials. The apparent negative effect of CEE/MPA on verbal memory does not appear to be age-dependent. Additional investigations are needed to understand the impact of other hormonally active compounds on dementia and cognitive outcomes.

Hormonal environment affects cognition independent of age during the menopause transition

CONTEXT

Cognitive decline is prevalent in aging populations, and cognitive complaints are common during menopause. However, the extent of hormonal influence is unclear, particularly when considered independent of the aging process.

OBJECTIVE

We sought to determine differences in cognitive function attributable to menopause, hypothesizing that differences would be associated with reproductive rather than chronological age.

DESIGN AND SETTING

In this cross-sectional study at a university hospital, we combined neuropsychological measures with functional magnetic resonance imaging to comprehensively assess cognitive function.

PARTICIPANTS

Sixty-seven menopausal women, aged 42-61 yr, recruited from a population-based menopause study, grouped into menopause stages based on hormonal and cycle criteria (premenopause, perimenopause, and postmenopause), participated in the study.

MAIN OUTCOME MEASURES

Neuropsychological and functional magnetic resonance imaging measures of verbal, visual, and executive cognitive function.

RESULTS

We found age-independent menopause effects on verbal function. Menopause groups differed in phonemic verbal fluency (F = 3.58, P < 0.019) and regional brain activation (inferior frontal cortex: corrected P < 0.000 right, P < 0.036 left; left prefrontal cortex: P < 0.012); left temporal pole: P < 0.001). Verbal measures correlated with estradiol and FSH (phonemic fluency: R = 0.249, P < 0.047 estradiol, R = -0.275, P < 0.029 FSH; semantic fluency: R = 0.318, P < 0.011 estradiol, R = -0.321, P < 0.010 FSH; right inferior frontal cortex: R = 0.364, P < 0.008 FSH; left inferior frontal cortex: R = -0.431, P < 0.001 estradiol, left prefrontal cortex: R = 0.279, P < 0.045 FSH; left temporal pole: R = -0.310, P < 0.024 estradiol, R = 0.451, P < 0.001 FSH; left parahippocampal gyrus: R = -0.278, P < 0.044 estradiol; left parietal cortex: R = -0.326, P < 0.017 estradiol).

CONCLUSIONS

Results suggest that verbal fluency mechanisms are vulnerable during the menopausal transition. Targeted intervention may preserve function of this critical cognitive domain.

The 2012 hormone therapy position statement of: The North American Menopause Society

OBJECTIVE

This position statement aimed to update the evidence-based position statement published by The North American Menopause Society (NAMS) in 2010 regarding recommendations for hormone therapy (HT) for postmenopausal women. This updated position statement further distinguishes the emerging differences in the therapeutic benefit-risk ratio between estrogen therapy (ET) and combined estrogen-progestogen therapy (EPT) at various ages and time intervals since menopause onset.

METHODS

An Advisory Panel of expert clinicians and researchers in the field of women's health was enlisted to review the 2010 NAMS position statement, evaluate new evidence, and reach consensus on recommendations. The Panel's recommendations were reviewed and approved by the NAMS Board of Trustees as an official NAMS position statement.

RESULTS

Current evidence supports the use of HT for perimenopausal and postmenopausal women when the balance of potential benefits and risks is favorable for the individual woman. This position statement reviews the effects of ET and EPT on many aspects of women's health and recognizes the greater safety profile associated with ET.

CONCLUSIONS

Recent data support the initiation of HT around the time of menopause to treat menopause-related symptoms and to prevent osteoporosis in women at high risk of fracture. The more favorable benefit-risk ratio for ET allows more flexibility in extending the duration of use compared with EPT, where the earlier appearance of increased breast cancer risk precludes a recommendation for use beyond 3 to 5 years.

Long term hormone therapy for perimenopausal and postmenopausal women

BACKGROUND

Hormone therapy (HT) is widely used for controlling menopausal symptoms and has also been used for the management and prevention of cardiovascular disease, osteoporosis and dementia in older women. This is an updated version of a Cochrane review first published in 2005.

OBJECTIVES

To assess the effects of long term HT on mortality, cardiovascular outcomes, cancer, gallbladder disease, fractures, cognition and quality of life in perimenopausal and postmenopausal women, both during HT use and after cessation of HT use.

SEARCH METHODS

We searched the following databases to February 2012: Cochrane Menstrual Disorders and Subfertility Group Trials Register, Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, PsycINFO.

SELECTION CRITERIA

We included randomised double-blind studies of HT versus placebo, taken for at least one year by perimenopausal or postmenopausal women. HT included oestrogens, with or without progestogens, via oral, transdermal, subcutaneous or intranasal routes.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed study quality and extracted data. We calculated risk ratios (RRS) for dichotomous data and mean differences (MDs) for continuous data, with 95% confidence intervals (CIs). Where findings were statistically significant, we calculated the absolute risk (AR) in the intervention group (the overall risk of an event in women taking HT).

MAIN RESULTS

Twenty-three studies involving 42,830 women were included. Seventy per cent of the data were derived from two studies (WHI 1998 and HERS 1998). Most participants were postmenopausal American women with at least some degree of co-morbidity, and the mean participant age in most studies was over 60 years. None of the studies focused on perimenopausal women. In relatively healthy postmenopausal women (that is generally fit, without overt disease) combined continuous HT significantly increased the risk of a coronary event (after one year's use: AR 4 per 1000, 95% CI 3 to 7), venous thrombo-embolism (after one year's use: AR 7 per 1000, 95% CI 4 to 11), stroke (after three years' use: AR 18 per 1000, 95% CI 14 to 23), breast cancer (after 5.6 years' use: AR 23 per 1000, 95% CI 19 to 29), gallbladder disease (after 5.6 years' use: AR 27 per 1000, 95% CI 21 to 34) and death from lung cancer (after 5.6 years' use plus 2.4 years' additional follow-up: AR 9 per 1000, 95% CI 6 to 13). Oestrogen-only HT significantly increased the risk of venous thrombo-embolism (after one to two years' use: AR 5 per 1000, 95% CI 2 to 10; after 7 years' use: AR 21 per 1000, 95% CI 16 to 28), stroke (after 7 years' use: AR 32 per 1000, 95% CI 25 to 40) and gallbladder disease (after seven years' use: AR 45 per 1000, 95% CI 36 to 57) but did not significantly increase the risk of breast cancer. Among women aged over 65 years who were relatively healthy and taking continuous combined HT, there was a statistically significant increase in the incidence of dementia (after 4 years' use: AR 18 per 1000, 95% CI 11 to 30). Among women with cardiovascular disease, long term use of combined continuous HT significantly increased the risk of venous thrombo-embolism (at one year: AR 9 per 1000, 95% CI 3 to 29). Women taking HT had a significantly decreased incidence of fractures with long term use (after 5.6 years of combined HT: AR 86 per 1000, 95% CI 79 to 84; after 7.1 years' use of oestrogen-only HT: AR 102 per 1000, 95% CI 91 to 112). Risk of fracture was the only outcome for which there was strong evidence of clinical benefit from HT. There was no strong evidence that HT has a clinically meaningful impact on the incidence of colorectal cancer.One trial analysed subgroups of 2839 relatively healthy 50 to 59 year old women taking combined continuous HT and 1637 taking oestrogen-only HT versus similar-sized placebo groups. The only significantly increased risk reported was for venous thrombo-embolism in women taking combined continuous HT: their absolute risk remained low, at less than 1/500. However, other differences in risk cannot be excluded as this study was not designed to have the power to detect differences between groups of women within 10 years of the menopause.

AUTHORS' CONCLUSIONS

HT is not indicated for primary or secondary prevention of cardiovascular disease or dementia, nor for preventing deterioration of cognitive function in postmenopausal women. Although HT is considered effective for the prevention of postmenopausal osteoporosis, it is generally recommended as an option only for women at significant risk, for whom non-oestrogen therapies are unsuitable. There are insufficient data to assess the risk of long term HT use in perimenopausal women or postmenopausal women younger than 50 years of age.

Estrogen neuroprotection and the critical period hypothesis

17β-Estradiol (estradiol or E2) is implicated as a neuroprotective factor in a variety of neurodegenerative disorders. This review focuses on the mechanisms underlying E2 neuroprotection in cerebral ischemia, as well as emerging evidence from basic science and clinical studies, which suggests that there is a "critical period" for estradiol's beneficial effect in the brain. Potential mechanisms underlying the critical period are discussed, as are the neurological consequences of long-term E2 deprivation (LTED) in animals and in humans after natural menopause or surgical menopause. We also summarize the major clinical trials concerning postmenopausal hormone therapy (HT), comparing their outcomes with respect to cardiovascular and neurological disease and discussing their relevance to the critical period hypothesis. Finally, potential caveats, controversies and future directions for the field are highlighted and discussed throughout the review.

Progestogens influence cognitive processes in aging

Steroid hormones may alter mnemonic processes. The majority of investigations have focused on the effects of 17β-estradiol (E(2)) to mediate learning. However, progesterone (P(4)), which varies across endogenous hormonal milieu with E(2), may also have effects on cognitive processes. P(4) may have effects in the hippocampus, prefrontal cortex (PFC) and/or striatum to enhance cognitive performance. Cognitive performance/learning has been assessed using tasks that are mediated by the hippocampus (water maze), PFC (object recognition) and striatum (conditioning). Our findings suggest that progestogens can have pervasive effects to enhance cognitive performance and learning in tasks mediated by the hippocampus, PFC and striatum and that these effects may be in part independent of actions at intracellular progestin receptors. Progestogens may therefore influence cognitive processes.

Anti-aβ therapeutics in Alzheimer's disease: the need for a paradigm shift

Most current Alzheimer's disease (AD) therapies in advanced phases of development target amyloid β-peptide (Aβ) production, aggregation, or accumulation. Translational models suggest that anti-Aβ therapies may be highly effective if tested as agents to prevent or delay development of the disease or as therapies for asymptomatic patients with very early signs of AD pathology. However, anti-Aβ therapeutics are currently being tested in symptomatic patients where they are likely to be much less effective or ineffective. The lack of alignment between human clinical studies and preclinical studies, together with predictions about optimal trial design based on our understanding of the initiating role of Aβ aggregates in AD, has created a treatment versus prevention dilemma. In this perspective, we discuss why it is imperative to resolve this dilemma and suggest ways for moving forward in the hopes of enhancing the development of truly effective AD therapeutics.

The impact of age-related ovarian hormone loss on cognitive and neural function

On average, women now live one-third of their lives after menopause. Because menopause has been associated with an elevated risk of dementia, an increasing body of research has studied the effects of reproductive senescence on cognitive function. Compelling evidence from humans, nonhuman primates, and rodents suggests that ovarian sex-steroid hormones can have rapid and profound effects on memory, attention, and executive function, and on regions of the brain that mediate these processes, such as the hippocampus and prefrontal cortex. This chapter will provide an overview of studies in humans, nonhuman primates, and rodents that examine the effects of ovarian hormone loss and hormone replacement on cognitive functions mediated by the hippocampus and prefrontal cortex. For humans and each animal model, we outline the effects of aging on reproductive function, describe how ovarian hormones (primarily estrogens) modulate hippocampal and prefrontal physiology, and discuss the effects of both reproductive aging and hormone treatment on cognitive function. Although this review will show that much has been learned about the effects of reproductive senescence on cognition, many critical questions remain for future investigation.

Timing of hormone therapy and dementia: the critical window theory revisited

OBJECTIVE

Although previous research has shown that initiation of postmenopausal estrogen hormone therapy (HT) in late life increases risk of dementia, animal studies and some observational studies have suggested that midlife use of HT may be beneficial; however, this has not been rigorously investigated in large population-based studies. Our objective was to compare HT use in midlife with that in late life on risk of dementia among 5,504 postmenopausal female members of an integrated healthcare delivery system.

METHODS

HT use was determined at midlife (mean age, 48.7 years) from a survey in 1964 and in late life (mean age, 76 years) using pharmacy databases from 1994 to 1998. Risk of dementia diagnosis was evaluated with inpatient and outpatient diagnoses made in Neurology, Neuropsychology, and Internal Medicine from 1999 to 2008. Cox proportional hazard models were used to examine effects of HT use at different times on dementia risk with adjustment for age, education, race, body mass index, number of children, and comorbidities.

RESULTS

A total of 1,524 women (27%) were diagnosed with dementia during the follow-up period. Compared to women never on HT, those taking HT only at midlife had a 26% decreased risk (multivariate adjusted hazards ratio [aHR], 0.74; 95% confidence interval [CI], 0.58-0.94 ), whereas those taking HT only in late life had a 48% increased risk (aHR, 1.48; 95% CI, 1.10-1.98), and women taking HT at both mid and late life had a similar risk of dementia (aHR, 1.02; 95% CI, 0.78-1.34 ).

INTERPRETATION

These findings suggest that use of HT in midlife only may protect against cognitive impairment, whereas HT initiation in late life could have deleterious effects.

Estrogen + progestin therapy and cognition: a randomized placebo-controlled double-blind study

AIMS

The use of hormone therapy (HT) is a relevant and topical issue in the treatment of menopausal symptoms in women. Information regarding the effects of combination treatment with estrogen and progesterone as well as treatment timing on cognitive function is lacking and was evaluated in healthy pre- and postmenopausal women.

METHODS

Sixteen premenopausal (45-51 years) and 16 postmenopausal (58-70 years) women were randomly assigned to receive either estrogen + progestin therapy (HT) or placebo (PL) for six months. The study was double-blind. Cognitive performance was measured at baseline and follow up with tests of verbal and visuomotor functions, verbal and visual memory, and attention.

RESULTS

In premenopausal women, cognitive attention, when compared to baseline, improved with HT but declined slightly with PL in the two-choice reaction time task (P = 0.049), while PL was associated with better performance in tests of shared attention (P = 0.024) and auditory attention (P < 0.05). In postmenopausal women, HT was associated with improved performance in verbal episodic memory (P = 0.024) and a minor decline in auditory attention (P = 0.025).

CONCLUSIONS

HT, with estradiol valerate and norethisterone, in healthy women showed only minor effects on attention around the menopausal transition and on memory in postmenopause.

Estrogen therapy and Alzheimer's dementia

Previous studies in postmenopausal women have reported that estrogen treatment (ET) modulates the risk for developing Alzheimer's disease (AD). It has recently been hypothesized that there may be a "critical period" around the time of menopause during which the prescription of ET may reduce the risk of developing AD in later life. This effect may be most significant in women under 49 years old. Furthermore, prescription of ET after this point may have a neutral or negative effect, particularly when initiated in women over 60-65 years old. In this paper, we review recent studies that use in vivo techniques to analyze the neurobiological mechanisms that might underpin estrogen's effects on the brain postmenopause. Consistent with the "critical period" hypothesis, these studies suggest that the positive effects of estrogen are most robust in young women and in older women who had initiated ET around the time of menopause.

Hormonal influences on cognition and risk for Alzheimer's disease

Research increasingly suggests that changes in estrogen levels during aging may increase the risk of Alzheimer's disease, the most common type of dementia. This update reviews the newest information about estrogen and cognitive aging, including information regarding the role of bioavailable estrogen in older women and men, use of selective estrogen receptor modulators to improve cognition, and studies of genetic risk factors to elucidate the effects of endogenous estrogen on aging and cognition. Future trials are needed to determine whether alternate timing, dosage, formulation, or method of administration of hormone replacement can reduce the risk of dementia.

Postmenopausal hormone therapy and cognition: effects of timing and treatment type

SETTING

Hormone therapy used for the management of postmenopausal symptoms in older women appears to result in variable effects on cognitive function, depending on study design, subjects, tests used, and types of therapy.

OBJECTIVE

To determine the effects of estrogen-only and estrogen plus progestogen preparations on cognitive performance (cognitive status, general and working memory) when taken 'early' and 'late' from the onset of menopause.

METHOD

The study consisted of 410 women who were participants in a longitudinal study, first recruited at age 40-80 years. They were tested for change over 5 years as an observational cohort by the Mini-Mental State Examination, National Adult Reading Test and the Wechsler Memory Scale Version 3. Cognitive decline, measured by age-adjusted scores, was defined as >or=10% negative change in each individual woman.

RESULTS

Controlling for age and lifestyle factors, and using the criterion of decrease in score >or=10% over 5 years for 'cognitive decline', 'early start' of hormone therapy (<3 years from menopause) was strongly associated with reduction in risk by the Mini-Mental State Examination (estrogen-only preparation, p = 0.005) but with increase in risk for general memory (with estrogen plus progestogen preparation, p = 0.02). Overall, there were no major effects on subgroups with type/timing of hormone therapy in relation to testing for a negative change in cognitive function.

CONCLUSION

'Early start' of estrogen-only hormone therapy was associated with reduced risk of global cognitive decline, and 'early start' estrogen-only and estrogen/progestogen hormone therapies showed increased risks of general memory decline. Even though this study did not have the power to discriminate between minor and mixed effects, it suggests that cognitive effects of hormone therapies may be mixed, depending on cognitive domain and timing of use/type of preparation.

[Alzheimer disease, memory and estrogen]

Epidemiological studies of Alzheimer disease have shown a higher prevalence of women. Some data argue for a link between Alzheimer disease and the decrease of estrogen in post-menopausal women. Animal studies have shown a beneficial effect of estrogen on memory with a decrease of amyloid deposition in models of AD, whereas estrogen has a positive effect on BDNF. Six studies have shown a positive effect of estrogen therapy on memory and studies on structural and functional imaging have shown a beneficial effect of estrogens but the largest study on prevention of dementia with estrogens (WHI) showed a deleterious effect. To better understand this paradoxical situation, we reviewed the literature on estrogens, memory and Alzheimer disease. We first discuss the promnesic effect of estrogen on mice and rats, second the neuroprotector effect of estrogen on animal models of Alzheimer disease, and third the available human studies. We hypothesize a link with the time of instauration of the estrogen treatment. Nevertheless this hypothesis remains to be demonstrated.

Estrogen therapy and cognition: a review of the cholinergic hypothesis

The pros and cons of estrogen therapy for use in postmenopausal women continue to be a major topic of debate in women's health. Much of this debate focuses on the potential benefits vs. harm of estrogen therapy on the brain and the risks for cognitive impairment associated with aging and Alzheimer's disease. Many animal and human studies suggest that estrogens can have significant beneficial effects on brain aging and cognition and reduce the risk of Alzheimer's-related dementia; however, others disagree. Important discoveries have been made, and hypotheses have emerged that may explain some of the inconsistencies. This review focuses on the cholinergic hypothesis, specifically on evidence that beneficial effects of estrogens on brain aging and cognition are related to interactions with cholinergic projections emanating from the basal forebrain. These cholinergic projections play an important role in learning and attentional processes, and their function is known to decline with advanced age and in association with Alzheimer's disease. Evidence suggests that many of the effects of estrogens on neuronal plasticity and function and cognitive performance are related to or rely upon interactions with these cholinergic projections; however, studies also suggest that the effectiveness of estrogen therapy decreases with age and time after loss of ovarian function. We propose a model in which deficits in basal forebrain cholinergic function contribute to age-related changes in the response to estrogen therapy. Based on this model, we propose that cholinergic-enhancing drugs, used in combination with an appropriate estrogen-containing drug regimen, may be a viable therapeutic strategy for use in older postmenopausal women with early evidence of mild cognitive decline.

Safety and efficacy of black cohosh and red clover for the management of vasomotor symptoms: a randomized controlled trial

OBJECTIVE

The aim of this study was to evaluate the safety and efficacy of black cohosh and red clover compared with placebo for the relief of menopausal vasomotor symptoms.

METHODS

This study was a randomized, four-arm, double-blind clinical trial of standardized black cohosh, red clover, placebo, and 0.625 mg conjugated equine estrogens plus 2.5 mg medroxyprogesterone acetate (CEE/MPA; n = 89). Primary outcome measures were reduction in vasomotor symptoms (hot flashes and night sweats) by black cohosh and red clover compared with placebo; secondary outcomes included safety evaluation, reduction of somatic symptoms, relief of sexual dysfunction, and overall improvement in quality of life.

RESULTS

Reductions in number of vasomotor symptoms after a 12-month intervention were as follows: black cohosh (34%), red clover (57%), placebo (63%), and CEE/MPA (94%), with only CEE/MPA differing significantly from placebo. Black cohosh and red clover did not significantly reduce the frequency of vasomotor symptoms as compared with placebo. Secondary measures indicated that both botanicals were safe as administered. In general, there were no improvements in other menopausal symptoms.

CONCLUSIONS

Compared with placebo, black cohosh and red clover did not reduce the number of vasomotor symptoms. Safety monitoring indicated that chemically and biologically standardized extracts of black cohosh and red clover were safe during daily administration for 12 months.

Menopause and mitochondria: windows into estrogen effects on Alzheimer's disease risk and therapy

Metabolic derangements and oxidative stress are early events in Alzheimer's disease pathogenesis. Multi-faceted effects of estrogens include improved cerebral metabolic profile and reduced oxidative stress through actions on mitochondria, suggesting that a woman's endogenous and exogenous estrogen exposures during midlife and in the late post-menopause might favourably influence Alzheimer risk and symptoms. This prediction finds partial support in the clinical literature. As expected, early menopause induced by oophorectomy may increase cognitive vulnerability; however, there is no clear link between age at menopause and Alzheimer risk in other settings, or between natural menopause and memory loss. Further, among older post-menopausal women, initiating estrogen-containing hormone therapy increases dementia risk and probably does not improve Alzheimer's disease symptoms. As suggested by the 'critical window' or 'healthy cell' hypothesis, better outcomes might be expected from earlier estrogen exposures. Some observational results imply that effects of hormone therapy on Alzheimer risk are indeed modified by age at initiation, temporal proximity to menopause, or a woman's health. However, potential methodological biases warrant caution in interpreting observational findings. Anticipated results from large, ongoing clinical trials [Early Versus Late Intervention Trial with Estradiol (ELITE), Kronos Early Estrogen Prevention Study (KEEPS)] will help settle whether midlife estrogen therapy improves midlife cognitive skills but not whether midlife estrogen exposures modify late-life Alzheimer risk. Estrogen effects on mitochondria adumbrate the potential relevance of estrogens to Alzheimer's disease. However, laboratory models are inexact embodiments of Alzheimer pathogenesis and progression, making it difficult to surmise net effects of estrogen exposures. Research needs include better predictors of adverse cognitive outcomes, biomarkers for risks associated with hormone therapy, and tools for monitoring brain function and disease progression.

Endogenous oestrogens predict 4-year decline in verbal fluency in postmenopausal women: the Rancho Bernardo Study

OBJECTIVE

Despite overwhelming biological plausibility, evidence for a protective effect of oestrogen on cognitive function in postmenopausal women is inconsistent. This study examines the association between endogenous oestrogen levels and subsequent 4-year decline in cognitive function test performance in community-dwelling older women.

DESIGN

Longitudinal cohort study.

PARTICIPANTS

Three hundred and forty-three postmenopausal women (median age 70 years).

MEASUREMENTS

Between 1984 and 1987, serum for measurement of sex hormones was obtained along with relevant covariates. Cognitive function was assessed in 1988-1991 and again in 1992-1996 using the Category Fluency test, the Mini-Mental Status Exam (MMSE) and Trail Making Test B (Trails B).

RESULTS

Women in the highest tertile of oestrone and bioavailable oestradiol had respectively 1.75 (95% CI 1.02, 3.07) and 1.79 (95% CI 1.04, 3.10) higher odds of 4 year decline in Category Fluency, a test of frontal lobe function, compared to those in the lowest tertile, independent of age and education. The 20% of women with highest tertile levels of both oestrone and bioavailable oestradiol had a twofold higher odds of verbal fluency loss (OR = 2.17; 95% CI 1.21, 3.89). Adjustment for testosterone levels or for obesity-related factors associated with high endogenous oestrogens (higher body mass index, waist girth, and triglycerides and lower high-density lipoprotein cholesterol) did not alter results. Neither oestrogen was associated with change in MMSE or Trails B scores.

CONCLUSIONS

Higher endogenous oestrogen levels were associated with a greater decline in verbal fluency in postmenopausal women. This association was not explained by elevated androgens or by obesity or obesity-related factors.

Aging, estrogens, and episodic memory in women

OBJECTIVE

To review the relation in midlife and beyond between estrogen exposures and episodic memory in women.

BACKGROUND

Episodic memory performance declines with usual aging, and impairments in episodic memory often portend the development of Alzheimer disease. In the laboratory, estradiol influences hippocampal function and animal learning. However, it is controversial whether estrogens affect memory after a woman's reproductive years.

METHOD

Focused literature review, including a summary of a systematic search of clinical trials of estrogens in which outcomes included an objective measure of episodic memory.

RESULTS

The natural menopause transition is not associated with the objective changes in episodic memory. Strong clinical trial evidence indicates that initiating estrogen-containing hormone therapy after the age of about 60 years does not benefit episodic memory. Clinical trial findings in middle-aged women before the age of 60 years are limited by smaller sample sizes and shorter treatment durations, but these also do not indicate substantial memory effects. Limited short-term evidence, however, suggests that estrogens may improve verbal memory after surgical menopause. Although hormone therapy initiation in old age increases dementia risk, observational studies raise the question of an early critical window during which midlife estrogen therapy reduces late-life Alzheimer disease. However, almost no data address whether midlife estrogen therapy affects episodic memory in old age.

CONCLUSIONS

Episodic memory is not substantially impacted by the natural menopause transition or improved by the use of estrogen-containing hormone therapy after the age of 60 years. Further research is needed to determine whether outcomes differ after surgical menopause or whether episodic memory later in life is modified by midlife estrogenic exposures.

Effects of botanicals and combined hormone therapy on cognition in postmenopausal women

OBJECTIVE

The aim of this study was to characterize the effects of red clover, black cohosh, and combined hormone therapy on cognitive function in comparison to placebo in women with moderate to severe vasomotor symptoms.

METHODS

In a phase II randomized, double-blind, placebo-controlled study, 66 midlife women (of 89 from a parent study; mean age, 53 y) with 35 or more weekly hot flashes were randomized to receive red clover (120 mg), black cohosh (128 mg), 0.625 mg conjugated equine estrogens plus 2.5 mg medroxyprogesterone acetate (CEE/MPA), or placebo. Participants completed measures of verbal memory (primary outcome) and other cognitive measures (secondary outcomes) before and during the 12th treatment month. A subset of 19 women completed objective, physiological measures of hot flashes using ambulatory skin conductance monitors.

RESULTS

Neither of the botanical treatments had an impact on any cognitive measure. Compared with placebo, CEE/MPA led to a greater decline in verbal learning (one of five verbal memory measures). This effect just missed statistical significance (P = 0.057) in unadjusted analyses but reached significance (P = 0.02) after adjusting for vasomotor symptoms. Neither of the botanical treatment groups showed a change in verbal memory that differed from the placebo group (Ps > 0.28), even after controlling for improvements in hot flashes. In secondary outcomes, CEE/MPA led to a decrease in immediate digit recall and an improvement in letter fluency. Only CEE/MPA significantly reduced objective hot flashes.

CONCLUSIONS

Results indicate that a red clover (phytoestrogen) supplement or black cohosh has no effects on cognitive function. CEE/MPA reduces objective hot flashes but worsens some aspects of verbal memory.

Estrogen therapy: is time of initiation critical for neuroprotection?

According to the 'critical period' hypothesis, which attempts to explain the observed discrepancies in the studies on estrogen and cognition, estrogen therapy effectively decreases cognitive decline in aging women when it is initiated around the time of menopause but not when it is started decades later. Here, I review studies in which the timing of the initiation of estrogen therapy was provided, to determine whether their findings support the 'critical period' hypothesis. The vast majority of the reviewed studies support the idea that early but not late initiation of estrogen therapy might prevent or delay cognitive decline in aging women. Nevertheless, numerous design issues, such as the specific drugs and doses that were used, the possible effects of progestins on cognition, and the failure to administer neuropsychological tests of specific cognitive domains that are sensitive to estrogen therapy confound the extant literature. In view of the reanalyzes of the Women's Health Initiative's data that show a beneficial effect of estrogen therapy on cardiac and breast diseases in women aged 50-59 years, more definitive evidence is needed to confirm that the early initiation of estrogen therapy that is continued for a few years provides enduring protection against cognitive aging 15-20 years later.

Frontiers proposal. National Institute on Aging "bench to bedside: estrogen as a case study"

On 28-29 September 2004, the National Institute on Aging (NIA) convened scientists for a workshop on the aging female brain focused on translating into clinical practice discoveries concerning estrogens and progestogens. Workshop objectives were to examine effects of estrogen and progestogen on brain and cognitive function in relation to aging, to examine consistencies and apparent discrepancies between Women's Health Initiative Memory Study findings and other research on cognitive function, to determine whether additional hormone interventions could be developed in this area, and to offer advice on design of clinical trials for other interventions that might ameliorate cognitive aging. Following the workshop, participants joined by other interested scientists organized into regional work groups to continue the dialogue begun in Bethesda and to propose recommendations for NIA. The resulting recommendations, referred to as the "Frontiers Proposal for Estrogen and Cognitive Aging", acknowledge the persistence of critical gaps in our understanding of how decline in ovarian steroid secretion during reproductive aging and use of ovarian steroid hormone therapy affect normal brain function and risk for late-life neurodegenerative disorders such as Alzheimer's disease. There is a pressing need for preclinical, human, and integrated studies on the relationship between the menopausal transition and midlife exposures to estrogens, progestogens and related compounds, and risks for age-associated cognitive disorders. Research is also needed on better predictors of adverse cognitive outcomes, valid biomarkers for risks associated with hormone therapy use, enhanced tools for monitoring brain function and disease progression, and novel forms of therapy for improving long-term cognitive outcomes.

Homocysteine lowering and cognition in CKD: the Veterans Affairs homocysteine study

BACKGROUND

Individuals with advanced chronic kidney disease (CKD) and end-stage renal disease (ESRD) have high plasma total homocysteine (tHcy) levels, which may be a risk factor for cognitive impairment. Whether treatment with high-dose B vitamins to decrease high tHcy levels improves cognition in persons with kidney disease is unknown.

STUDY DESIGN

Randomized controlled trial.

SETTING & PARTICIPANTS

A substudy of 659 patients (mean age, 67.3 +/- 11.7 years) who participated in a randomized double-blind clinical trial 5 years in duration conducted in 36 US Department of Veterans Affairs medical centers of the effect on all-cause mortality of vitamin-induced lowering of plasma tHcy level. 236 (35.8%) were treated by using dialysis (ESRD) and 423 (64.2%) had a Cockcroft-Gault estimated creatinine clearance of 30 mL/min or less (advanced CKD). All had high tHcy levels (> or =15 micromol/L) at baseline. Cognitive assessments began during the follow-up period of the main trial 3 years after treatment began; participants subsequently were retested 1 year later to assess cognitive change.

INTERVENTION

Daily high-dose B vitamin capsule (40 mg of folic acid, 100 mg of vitamin B(6), and 2 mg of vitamin B(12)) or placebo.

OUTCOMES

Cognitive function at initial assessment and 1 year later.

MEASUREMENTS

Telephone Interview of Cognitive Status-modified, supplemented with attention, working memory, and executive function tests.

RESULTS

Initial cognitive function was impaired in approximately 19% of patients regardless of treatment assignment (vitamin or placebo) or kidney disease status (advanced CKD or ESRD). Treatment decreased tHcy levels by 26.7%. Unadjusted and adjusted analyses showed that treatment did not improve initial cognitive outcomes or affect subsequent cognitive status 1 year later.

LIMITATIONS

Cognitive assessments began after treatment was initiated; cognitive assessment was limited.

CONCLUSION

Treatment with high daily doses of B vitamins, which decreased tHcy levels, did not affect cognitive outcomes in patients with advanced CKD and ESRD.

Hormone therapy and cognitive function

BACKGROUND

Clinical trials yield discrepant information about the impact of hormone therapy on verbal memory and executive function. This issue is clinically relevant because declines in verbal memory are the earliest predictor of Alzheimer's disease and declines in executive function are central to some theories of normal, age-related changes in cognition.

METHODS

We conducted a systematic review of randomized clinical trials of hormone therapy (i.e. oral, transdermal, i.m.) and verbal memory, distinguishing studies in younger (i.e. <or=65 years of age; n = 9) versus older (i.e. >65 years; n = 7) women and studies involving estrogen alone versus estrogen plus progestogen. Out of 32 placebo-controlled trials, 17 were included (13 had no verbal memory measures and 2 involved cholinergic manipulations). We also provide a narrative review of 25 studies of executive function (two trials), since there are insufficient clinical trial data for systematic review.

RESULTS

There is some evidence for a beneficial effect of estrogen alone on verbal memory in younger naturally post-menopausal women and more consistent evidence from small-n studies of surgically post-menopausal women. There is stronger evidence of a detrimental effect of conjugated equine estrogen plus medroxyprogesterone acetate on verbal memory in younger and older post-menopausal women. Observational studies and pharmacological models of menopause provide initial evidence of improvements in executive function with hormone therapy.

CONCLUSIONS

Future studies should include measures of executive function and should address pressing clinical questions; including what formulation of combination hormone therapy is cognitively neutral/beneficial, yet effective in treating hot flashes in the early post-menopause.

Endogenous and exogenous estrogen, cognitive function, and dementia in postmenopausal women: evidence from epidemiologic studies and clinical trials

There are more than 200 published scientific papers showing that estrogen has favorable effects on brain tissue and physiology in cell culture and animal models including non-human primates. The biological plausibility for a neuroprotective estrogen effect is overwhelming. However, most studies of endogenous estrogen and cognitive decline or dementia in women fail to show protection, and some suggest harm. Failure to find any consistent association might reflect the limitations of a single time of estrogen assay or poor assay sensitivity. More than half of the observational studies of hormone therapy suggest benefit. Nearly all long-term clinical trials fail to show benefit, and the longer trials tend to show harm. Failure to adequately adjust for self-selection of healthier and wealthier women and publication bias could account for some, or all, of the protective effect attributed to estrogen in observational studies. Overall, the evidence does not convincingly support the prescription of early or late postmenopausal estrogen therapy to preserve cognitive function or prevent dementia.

Estrogens, episodic memory, and Alzheimer's disease: a critical update

Estrogen-containing hormone therapy initiated during late postmenopause does not improve episodic memory (an important early symptom of Alzheimer's disease), and it increases dementia risk. Cognitive consequences of exogenous estrogen exposures during midlife are less certain. Observational evidence implies that use of hormone therapy at a younger age close to the time of menopause may reduce risk of Alzheimer's disease later in life. However, there are concerns that observational findings may be systematically biased. Partial insight on this critical issue may be gleaned from results of ongoing clinical trials involving midlife postmenopausal women (Early versus Late Intervention Trial with Estrogen; Kronos Early Estrogen Prevention Study). The effects of exogenous midlife estrogen exposures and Alzheimer risk can also be approached through better animal models, through carefully designed cohort studies, and through use of surrogate outcomes in randomized controlled trials in midlife women. Selective estrogen receptor modulators have the potential to affect cognitive outcomes and also merit additional study.

Mechanisms of action of estrogen in the brain: insights from human neuroimaging and psychopharmacologic studies

Use of estrogen therapy in the perimenopausal and postmenopausal periods has been shown in several clinical trials to help women maintain a premenopausal level of cognitive function. What is not yet fully understood is how the neurobiological effects of estrogen contribute to these cognitive effects. This review explores data from two related bodies of human literature that provide compelling evidence in support of the biological plausibility that estrogen treatment can benefit cognition. The first half of the literature review focuses on studies from the estrogen neuroimaging literature, and the second half focuses on pharmacologic challenge studies assessing estrogen-neurotransmitter interactions. We integrate these two bodies of literature by focusing on the neurophysiologic underpinnings of estrogen effects on cognition and linking these clinical studies to preclinical studies. The focus on verbal memory is important because it is a cognitive function that has been shown to change with estrogen treatment and predict Alzheimer's disease risk but is not addressed by preclinical studies. Overall, we conclude that estrogen interacts with cholinergic and serotonergic systems to affect hippocampal and frontal cortical brain areas and thereby enhance memory, particularly at the retrieval stage.

Long term hormone therapy for perimenopausal and postmenopausal women

BACKGROUND

Hormone therapy (HT) is widely used for controlling menopausal symptoms and has also been used for the management and prevention of cardiovascular disease, osteoporosis and dementia in older women. This is an updated version of the original Cochrane review first published in 2005.

OBJECTIVES

To assess the effect of long-term HT on mortality, cardiovascular outcomes, cancer, gallbladder disease, cognition, fractures and quality of life.

SEARCH STRATEGY

We searched the following databases to November 2007: Trials Register of the Cochrane Menstrual Disorders and Subfertility Group, Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, Biological Abstracts. Also relevant non-indexed journals and conference abstracts.

SELECTION CRITERIA

Randomised double-blind trials of HT versus placebo, taken for at least one year by perimenopausal or postmenopausal women. HT included oestrogens, with or without progestogens, via oral, transdermal, subcutaneous or transnasal routes.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data.

MAIN RESULTS

Nineteen trials involving 41,904 women were included. In relatively healthy women, combined continuous HT significantly increased the risk of venous thrombo-embolism or coronary event (after one year's use), stroke (after three years), breast cancer and gallbladder disease. Long-term oestrogen-only HT significantly increased the risk of venous thrombo-embolism, stroke and gallbladder disease (after one to two years, three years and seven years' use respectively), but did not significantly increase the risk of breast cancer. The only statistically significant benefits of HT were a decreased incidence of fractures and (for combined HT) colon cancer, with long-term use. Among women aged over 65 who were relatively healthy (i.e. generally fit, without overt disease) and taking continuous combined HT, there was a statistically significant increase in the incidence of dementia. Among women with cardiovascular disease, long-term use of combined continuous HT significantly increased the risk of venous thrombo-embolism.One trial analysed subgroups of 2839 relatively healthy 50 to 59 year old women taking combined continuous HT and 1637 taking oestrogen-only HT, versus similar-sized placebo groups. The only significantly increased risk reported was for venous thrombo-embolism in women taking combined continuous HT: their absolute risk remained low, at less than 1/500. However, this study was not powered to detect differences between groups of younger women.

AUTHORS' CONCLUSIONS

HT is not indicated for the routine management of chronic disease. We need more evidence on the safety of HT for menopausal symptom control, though short-term use appears to be relatively safe for healthy younger women.

Life-time estrogen exposure and cognitive functioning in later life

CONTEXT

While recent studies suggest that exogenous estrogen treatment could help reduce age-related cognitive decline and delay the onset of dementia, this has not been found consistently. Few studies have considered the influence of life-time estrogen exposure which may have an independent effect on cognition and/or modulate treatment response.

OBJECTIVE

The aim of this study was to examine whether factors related to estrogen exposure across the life-time were associated with cognitive function in postmenopausal women.

DESIGN

A battery of cognitive tests were administered at baseline and at 2 and 4 years of follow-up to evaluate cognitive performance among a population-based cohort of 996 French women aged 65 years or older, who were recruited as part of the ESPRIT study. Detailed reproductive histories were also obtained. Logistic regression models, controlling for an extensive range of potential confounding factors, were generated to determine whether hormone-related factors across a woman's lifetime were associated with poor cognitive performance in later life.

RESULTS

Age at first menses was negatively associated with performance on the tasks of visual memory and psychomotor speed, while a longer reproductive period was associated with better verbal fluency. Likewise, women who had their first child at a young age performed significantly worse on each of these tasks, as well as on a measure of global cognitive function. The results also suggest that current hormone therapy may be beneficial for a number of cognitive domains, however, in multivariate analysis, women performed significantly better on the task of visual memory only. In contrast, in analysis adjusted for baseline cognitive performance and a range of other factors, none of the reproductive variables were associated with a decline in cognitive performance or the incidence of dementia during the 4-year follow-up period.

CONCLUSIONS

In addition to hormone therapy, certain hormone-related events across the lifetime are also associated with cognitive functioning in later life. They were not observed in this study to modulate dementia risk; however, this should be verified over a longer follow-up period. Further studies will also be required to determine whether lifetime hormonal exposure may modify women's response to hormone therapy after the menopause.

Cognitive changes after menopause: influence of estrogen

The natural menopause is not associated with substantial cognitive change. Limited clinical trial evidence suggests that estrogen-containing hormone therapy has little effect on cognition during midlife, but prompt initiation after surgical menopause may improve aspects of memory. Among older postmenopausal women, strong clinical trial evidence demonstrates that hormone initiation does not improve cognition. More limited clinical trial evidence indicates no improvement in Alzheimer symptoms, and the Women's Health Initiative Memory Study found an increase in dementia risk among older women. Observational findings of reduced Alzheimer risk may reflect early hormone use in younger women, or findings may be biased. Cognitive effects of selective estrogen receptor modulators are not yet well studied.

Estrogen replacement therapy induces functional asymmetry on an odor memory/discrimination test

The secondary afferents of the olfactory system largely project to the ipsilateral cortex without synapsing in the thalamus, making unilateral olfactory testing a useful probe of ipsilateral hemispheric activity. In light of evidence that lateralized performance on some perceptual tasks may be influenced by estrogen, we assessed left:right nostril differences in two measures of olfactory function in 14 post-menopausal women receiving estrogen replacement therapy (ERT) and 48 post-menopausal women receiving no such therapy. Relative to women not taking ERT, those receiving ERT exhibited better performance in the left nostril and poorer performance in the right nostril on an odor memory/discrimination test. Similar laterality effects were not observed for an odor detection threshold test employing phenyl ethyl alcohol. These results suggest that estrogen influences the lateralization of an odor memory/discrimination task and that hormone replacement therapy in the menopause may be an excellent paradigm for understanding lateralizing effects of hormones on some sensory processes.

Estrogen and progestogen use in postmenopausal women: July 2008 position statement of The North American Menopause Society

OBJECTIVE

: To update for both clinicians and the lay public the evidence-based position statement published by The North American Menopause Society (NAMS) in March 2007 regarding its recommendations for menopausal hormone therapy (HT) for postmenopausal women, with consideration for the therapeutic benefit-risk ratio at various times through menopause and beyond.

DESIGN

: An Advisory Panel of clinicians and researchers expert in the field of women's health was enlisted to review the March 2007 NAMS position statement, evaluate new evidence through an evidence-based analysis, and reach consensus on recommendations. The Panel's recommendations were reviewed and approved by the NAMS Board of Trustees as an official NAMS position statement. The document was provided to other interested organizations to seek their endorsement.

RESULTS

: Current evidence supports a consensus regarding the role of HT in postmenopausal women, when potential therapeutic benefits and risks around the time of menopause are considered. This paper lists all these areas along with explanatory comments. Conclusions that vary from the 2007 position statement are highlighted. Addenda include a discussion of risk concepts, a new component not included in the 2007 paper, and a recommended list of areas for future HT research. A suggested reading list of key references is also provided.

CONCLUSIONS

: Recent data support the initiation of HT around the time of menopause to treat menopause-related symptoms; to treat or reduce the risk of certain disorders, such as osteoporosis or fractures in select postmenopausal women; or both. The benefit-risk ratio for menopausal HT is favorable close to menopause but decreases with aging and with time since menopause in previously untreated women.

Hormone replacement therapy for cognitive function in postmenopausal women

BACKGROUND

As estrogens have been found in animal models to be associated with the maintenance and protection of brain structures, it is biologically plausible that maintaining high levels of estrogens in postmenopausal women by medication could be protective against cognitive decline.

OBJECTIVES

To investigate the effect of ERT (estrogens only) or HRT (estrogens combined with a progestagen) in comparison with placebo in RCTs on cognitive function in postmenopausal women.

SEARCH STRATEGY

The CDCIG Specialized Register was searched 7 March 2006. Additional searches were made of MEDLINE (1966-2006/02); EMBASE (1985-2006/02); PsycINFO (1967-2006/02) and CINAHL (1982-2006/01).

SELECTION CRITERIA

All double-blind RCTs trials of the effect of ERT or HRT on cognitive function over a treatment period of at least two weeks in postmenopausal women.

DATA COLLECTION AND ANALYSIS

Selection of studies, assessment of quality and extraction of data were undertaken independently by three reviewers with disagreements resolved by discussion.

MAIN RESULTS

In total, 24 trials were included, but only 16 (10,114 women) had analysable data. Meta-analyses showed no effects of either ERT or HRT on prevention of cognitive impairment after five and four years of treatment, respectively (odds ratio 1.34, 95% CI 0.95 to 1.9; odds ratio 1.05, 95% CI 0.72 to 1.54 respectively) (trend favouring control in both instances). Analyses assessing the effects of treatment over time found that both ERT and HRT did not maintain or improve cognitive function and may even adversely affect this outcome (WMD = -0.45, 95% CI -0.99 to 0.09; WMD = -0.16, 95% CI -0.58 to 0.26, respectively at maximum follow up). Negative effects were found for ERT after one year and HRT after three and four years of therapy. Results from smaller trials assessing effects on individual cognitive domains mostly reported no evidence of benefit.

AUTHORS' CONCLUSIONS

There is good evidence that both ERT and HRT do not prevent cognitive decline in older postmenopausal women when given as short term or longer term (up to five years) therapy. It is not known whether either specific types of ERT or HRT have specific effects in subgroups of women, although there was evidence that combined hormone therapy in similarly aged women was associated with a decrement in a number of verbal memory tests and a small improvement in a test of figural memory. There is insufficient evidence to determine whether subgroups of women using specific types of hormone therapy could benefit from treatment. It remains to be determined whether factors such as younger age (< 60 years of age), type of menopause (surgical or natural) and type of treatment (type of estrogen with or without a progestagen), mode of delivery (transdermal, oral or intramuscular) and dosage have positive effects at a clinically relevant level. In addition, whether the absence or presence of menopausal symptoms can modify treatment effects should be investigated in more detail. Large RCTs currently underway in the USA may be able to provide answers to these uncertainties by the year 2010. In the meantime, based on the available evidence, ERT or HRT cannot be recommended for overall cognitive improvement or maintenance in older postmenopausal women without cognitive impairment.

Cognition and cognitive aging

Cognitive effects of estrogen have been considered in a number of large, randomized, double-blind, placebo-controlled trials. Most have involved older, postmenopausal women, and results of these provide little support for the view that estrogen-containing hormone therapy initiated after age 60 substantially affects mean cognitive performance over periods of time ranging up to 5 years. This conclusion appears particularly true for episodic memory, a cognitive domain in which impairments are associated with increased risk of Alzheimer's disease. Other domains have been less thoroughly assessed. For women undergoing surgical menopause, limited clinical trial evidence suggests that prompt initiation of estrogen therapy may benefit verbal episodic memory, at least over a period of several months. Among middle-aged women, observational studies indicate no important deleterious effect of the natural menopause transition on cognitive performance. Similarly, limited clinical trial evidence from middle-aged postmenopausal women implies no substantial effect of hormone therapy on episodic memory, at least over the short term. Unfortunately, no randomized clinical trials have addressed long-term cognitive outcomes of hormone therapy started during the menopausal transition or early postmenopause, a time hypothesized to represent a 'critical window' of opportunity. There is urgent need for research in this area, and at least two clinical trials now underway may eventually provide partial answers.

Estradiol interacts with the cholinergic system to affect verbal memory in postmenopausal women: evidence for the critical period hypothesis

Estradiol has been shown to interact with the cholinergic system to affect cognition in postmenopausal women. This study further investigated the interaction of estradiol and cholinergic system functioning on verbal memory and attention in two groups of healthy younger (ages 50-62) and older (ages 70-81) postmenopausal women. Twenty-two postmenopausal women were randomly and blindly placed on 1 mg of 17-beta estradiol orally for 1 month then 2 mg for 2 months or matching placebo pills after which they participated in three anticholinergic challenge sessions when verbal memory and attention were assessed. Subjects were administered either the antimuscarinic drug scopolamine (SCOP), the antinicotinic drug mecamylamine (MECA), or placebo. After the first challenge phase, they were crossed over to the other hormone treatment for another 3 months and repeated the challenges. Results showed that estradiol pretreatment significantly attenuated the anticholinergic drug-induced impairments on a test of episodic memory (the Buschke Selective Reminding Task) for the younger group only, while estradiol treatment impaired performance of the older group. The results suggest that younger subjects may experience more cholinergic benefit from estradiol treatment than older subjects, supporting the concept of a critical period for postmenopausal estrogen use.

Prevention therapeutics of dementia

In the absence of effective drugs for Alzheimer's disease (AD) and a validated roadmap or guideline for drug development, it is important to consider some of the limitations currently hampering AD drug development and some general principles for moving forward. This paper will address current barriers to developing drugs for AD, and offer new considerations for accelerating drug discovery, development, and clinical trials.

Estrogen receptor alpha and beta differentially regulate intracellular Ca(2+) dynamics leading to ERK phosphorylation and estrogen neuroprotection in hippocampal neurons

Our previous analyses indicated that both estrogen receptor (ER) subtypes, ERalpha and ERbeta, contribute to estrogen neuroprotection [Zhao, L., Wu, T.-W., Brinton, R.D., 2004. Estrogen receptor subtypes alpha and beta contribute to neuroprotection and increased Bcl-2 expression in primary hippocampal neurons. Brain Res. 1010, 22-34]. In the present study, we sought to determine the underlying mechanisms by which ERalpha and ERbeta promote neuronal function, with a focus on neuroprotection, and whether these mechanisms are consistent with a classical nuclear or membrane ER-mediated response. Results of these analyses demonstrated that both the ERalpha-selective agonist, PPT (100 pM), and the ERbeta-selective agonist, DPN (100 pM), were effective in dynamically but differentially regulating intracellular calcium (Ca(2+)) signaling in hippocampal neurons. Consistent with the direct measurement of neuroprotective outcomes [Zhao, L., Wu, T.-W., Brinton, R.D., 2004. Estrogen receptor subtypes alpha and beta contribute to neuroprotection and increased Bcl-2 expression in primary hippocampal neurons. Brain Res. 1010, 22-34], PPT and DPN exerted comparable efficacy in attenuating excitotoxic glutamate (200 microM)-induced intracellular Ca(2+) rise. In contrast, DPN was more efficacious than PPT in potentiating a physiological concentration of glutamate (25 microM)-induced intracellular Ca(2+) rise in these neurons. Further analyses revealed that both PPT and DPN increased ERK phosphorylation, however, the temporal profile and magnitude of response were unique to each molecule. The presence of the L-type Ca(2+) channel inhibitor, nifedipine (10 microM), partially inhibited 17beta-estradiol- and PPT-induced increase in phosphorylated ERK expression, whereas it induced a complete inhibition of DPN-induced increase in ERK phosphorylation. Additional neuroprotective experiments demonstrated that the MAPK inhibitor, PD 98059 (5 microM), partially blocked 17beta-estradiol-induced promotion of neuronal survival against excitotoxic glutamate (200 microM)-induced neurotoxicity, whereas it completely blocked both PPT- and DPN-induced neuroprotection. The presence of the nuclear ER antagonist, ICI 182,780 (1 microM), not only failed to block all 3 molecule-induced neuroprotection, but coadministration of ICI 182,780 and each single molecule exerted a comparable or even greater neuroprotection. Taken together, as an expansion of our previous analyses, these data indicate that both ERalpha and ERbeta contribute to neuronal mechanisms leading to estrogen promotion of neuronal function but with unique signaling profiles. Activation of ERbeta and induction of intracellular Ca(2+) influx via the L-type channels appears to be more closely associated with estrogen promotion of memory mechanisms. However, ERalpha and ERbeta play an equivalently important role in mediating estrogen neuroprotection, and, which is dependent upon the activation of the MAPK signaling. Further, the present analyses suggest that separate from a classical nuclear ER-mediated response, estrogen promotes neuronal survival likely through a non-nuclear cytoplasm or membrane-associated ER-mediated rapid signaling cascade.