Impact of estrogen use on decline in cognitive function in a representative sample of older community-resident women

Reading activity prevents long-term decline in cognitive function in older people: evidence from a 14-year longitudinal study

OBJECTIVE

This study examined the effect of daily life reading activity on the risk of cognitive decline and whether the effect differs regarding education levels.

DESIGN

A longitudinal study with 6-, 10-, and 14-year follow-up.

SETTING

Face-to-face interviews with structured questionnaires at home.

PARTICIPANTS

A representative sample of 1,962 Taiwanese community-dwelling older persons aged 64 and above, followed up in four waves of surveys over 14 years.

MEASUREMENTS

Baseline reading frequencies were measured based on a scale of leisure activity. The Short Portable Mental Status Questionnaire was used to measure cognitive performance. We performed logistic regression to assess associations between baseline reading and later cognitive decline. Interaction terms between reading and education were to compare the reading effects on cognitive decline at different education levels.

RESULTS

After adjusting for covariates, those with higher reading frequencies (≥1 time a week) were less likely to have cognitive decline at 6-year (adjusted odds ratio [AOR]: 0.54; 95% confidence interval [CI]: 0.34-0.86), 10-year (AOR: 0.58, 95% CI: 0.37-0.92), and 14-year (AOR: 0.54, 95% CI: 0.34-0.86); in a 14-year follow-up, a reduced risk of cognitive decline was observed among older people with higher reading frequencies versus lower ones at all educational levels.

CONCLUSIONS

Reading was protective of cognitive function in later life. Frequent reading activities were associated with a reduced risk of cognitive decline for older adults at all levels of education in the long term.

Comparative analysis of cognitive impairment prevalence and its etiological subtypes in a rural area of northern China between 2010 and 2015

The purpose of this study was to evaluate changes in the prevalence and risk factors of cognitive impairment (CI) by analyzing and comparing two cross-sectional epidemiological surveys of CI and its subtypes were performed in a rural area of northern China between 2010 and 2015. Residents aged ≥60 years were drawn in northern China. The Mini Mental State Examination (MMSE) is recommended to test for CI. Dementia was further categorised into Alzheimer’s disease (AD), vascular dementia (VaD), and dementia caused by other diseases (ODs). Mild cognitive impairment (MCI) was classified into MCI caused by AD (MCI-A), MCI caused by VaD (MCI-VD), and MCI caused by ODs (MCI-O). The prevalence of CI increased in China. The prevalence of all-cause CI was 30·5% (22.9% MCI and 7.6% dementia) in 2010. The prevalence of all-cause CI was 38.3% (27.8% MCI and 10.5% dementia) in 2015. Similar increases were observed for the prevalence of subtypes of dementia and MCI. These findings suggest an increasing prevalence of CI and its subtypes in China, which may be related to alterations in sociodemographic factors, vascular risk factors and lifestyle changes over time in these cohorts.

17β-estradiol replacement therapy protects myelin sheaths in the white matter of middle-aged female ovariectomized rats: a stereological study

Many studies have shown that estrogen replacement therapy (ERT) can improve cognitive function and affect the structure of the brain, including the white matter, in postmenopausal women. However, it is unclear whether ERT plays an important role in white matter remodeling in postmenopausal women. In the present study, middle-aged (9-12-month-old) female Sprague-Dawley rats were bilaterally ovariectomized (OVX) and randomly allocated to the vehicle treatment (OVX+Veh) group or the 17β-estradiol replacement (OVX+E) group. After 1 month of treatment, spatial learning and memory capacities were assessed using the Morris water maze task. Then, stereological methods were used to quantitatively evaluate white matter volume and myelinated fiber parameters of the white matter in the 2 groups of rats. The results revealed that the mean escape latency of the OVX+E rats in the Morris water maze task was significantly shorter than that of the OVX+Veh rats. The volume density of the myelinated fibers and the volume density and total volume of the myelin sheaths were significantly greater in the OVX+E rats than in the OVX+Veh rats. However, there were no significant differences in white matter volume or in the total length or volume of myelinated fibers in white matter between the 2 groups of rats. Our results showed that 1 month of ERT had significant beneficial effects on spatial learning capacity and on the myelin sheaths and myelinated fibers in the white matter of middle-aged OVX rats.

Sex-specific risk of cardiovascular disease and cognitive decline: pregnancy and menopause

Understanding the biology of sex differences is integral to personalized medicine. Cardiovascular disease and cognitive decline are two related conditions, with distinct sex differences in morbidity and clinical manifestations, response to treatments, and mortality. Although mortality from all-cause cardiovascular diseases has declined in women over the past five years, due in part to increased educational campaigns regarding the recognition of symptoms and application of treatment guidelines, the mortality in women still exceeds that of men. The physiological basis for these differences requires further research, with particular attention to two physiological conditions which are unique to women and associated with hormonal changes: pregnancy and menopause. Both conditions have the potential to impact life-long cardiovascular risk, including cerebrovascular function and cognition in women. This review draws on epidemiological, translational, clinical, and basic science studies to assess the impact of hypertensive pregnancy disorders on cardiovascular disease and cognitive function later in life, and examines the effects of post-menopausal hormone treatments on cardiovascular risk and cognition in midlife women. We suggest that hypertensive pregnancy disorders and menopause activate vascular components, i.e., vascular endothelium and blood elements, including platelets and leukocytes, to release cell-membrane derived microvesicles that are potential mediators of changes in cerebral blood flow, and may ultimately affect cognition in women as they age. Research into specific sex differences for these disease processes with attention to an individual's sex chromosomal complement and hormonal status is important and timely.

Therapeutic approaches to age-associated neurocognitive disorders

The United Nations projects that the number of individuals with dementia in developed countries alone will be approximately 36,7 million by the year 2050. International recognition of the significant emotional and economic burden of Alzheimer's disease has been matched by a dramatic increase in the development of pharmacological and nonpharmacological approaches to this illness in the past decade. Changing demographics have underscored the necessity to develop similar approaches for the remediation of the cognitive impairment associated with more benign syndromes, such as mild cognitive impairment (MCI) and age-associated cognitive decline (AACD). The present article aims to provide an overview of the most current therapeutic approaches to age-associated neurocognitive disorders. Additionally, it discusses the conceptual and methodological issues that surround the design, implementation, and interpretation of such approaches.

Individualizing hormone therapy to minimize risk: accurate assessment of risks and benefits

Contrary to the exaggerated risks associated with HRT that developed after the initial press reports held by the Women's Health Initiative (WHI) writing group, the recent approach to hormone therapy is more balanced and evidence based. A review of over 40 years of scientific studies demonstrates that estrogen is a medication that can decrease mortality, cardiovascular disease, osteoporosis fracture, urogenital atrophy and dementia. When timing of administration, dose of therapy and route of administration are considered, estrogen is associated with low risks and substantial benefits. The decision of whether or not to take HRT for either short symptom relief or for long-term therapy, should be based on an accurate risk-benefit analysis. Adjusting the dose of therapy and considering a transdermal approach, particularly in high-risk patients, are important considerations.

Postmenopausal hormone therapy, timing of initiation, APOE and cognitive decline

Associations between postmenopausal hormone therapy (HT) and cognitive decline may depend on apolipoprotein E (APOE) status or timing of initiation. We included 16,514 Nurses' Health Study participants aged 70-81 years who were followed since 1976 and completed up to 3 telephone cognitive assessments (2 years apart), between 1995 and 2006. The tests assessed general cognition (Telephone Interview of Cognitive Status; TICS), verbal memory, and category fluency. We used longitudinal analyses to estimate differences in cognitive decline across hormone groups. APOE genotype was available in 3697 participants. Compared with never users, past or current HT users showed modest but statistically significant worse rates of decline in the TICS: the multivariable-adjusted difference in annual rate of decline in the TICS among current estrogen only users versus never users was -0.04 (95% confidence interval, -0.07 to -0.004); for current estrogen + progestin users, the mean difference was -0.05 (95% confidence interval, -0.10 to -0.002). These differences were equivalent to those observed in women who are 1-2 years apart in age. We observed no protective associations with early timing of hormone initiation. We found suggestive interactions with APOE e4 status (e.g., on TICS, p interaction, 0.10), where the fastest rate of decline was observed among APOE e4 carriers who were current HT users. Regardless of timing of initiation, HT may be associated with worse rates of decline in general cognition, especially among those with an APOE e4 allele.

Evaluation of prefrontal-hippocampal effective connectivity following 24 hours of estrogen infusion: an FDG-PET study

Although several functional neuroimaging studies have addressed the relevance of hormones to cerebral function, none have evaluated the effects of hormones on network effective connectivity. Since estrogen enhances synaptic connectivity and has been shown to drive activity across neural systems, and because the hippocampus and prefrontal cortex (PFC) are putative targets for the effects of estrogen, we hypothesized that effective connectivity between these regions would be enhanced by an estrogen challenge. In order to test this hypothesis, FDG-PET scans were collected in eleven postmenopausal women at baseline and 24h after a graded estrogen infusion. Subtraction analysis (SA) was conducted to identify sites of increased cerebral glucose uptake (CMRglc) during estrogen infusion. The lateral PFC and hippocampus were a priori sites for activation; SA identified the right superior frontal gyrus (RSFG; MNI coordinates 18, 60, 28) (SPM2, Wellcome Dept. of Cognitive Neurology, London, UK) as a site of increased CMRglc during estrogen infusion relative to baseline. Omnibus covariate analysis conducted relative to the RSFG identified the right hippocampus (MNI coordinates: 32, -32, -6) and right middle frontal gyrus (RMFG; MNI coordinates: 40, 22, 52) as sites of covariance. Path analysis (Amos 5.0 software) revealed that the path coefficient for the RSFG to RHIP path differed from zero only during E2 infusion (p<0.05); moreover, the magnitude of the path coefficient for the RHIP to RMFG path showed a significant further increase during the estrogen infusion condition relative to baseline [Deltachi(2)=4.05, Deltad.f.=1, p=0.044]. These findings are consistent with E2 imparting a stimulatory effect on effective connectivity within prefrontal-hippocampal circuitry. This holds mechanistic significance for resting state network interactions and may hold implications for mood and cognition.

Brain aging modulates the neuroprotective effects of estrogen on selective aspects of cognition in women: a critical review

Although there is now a substantial literature on the putative neuroprotective effects of estrogen on cognitive functioning in postmenopausal women, it is replete with inconsistencies. The critical period hypothesis, posited several years ago, attempts to account for the discrepancies in this literature by positing that estrogen treatment (ET) will protect aspects of cognition in older women only when treatment is initiated soon after the menopause. Indeed, evidence from basic neuroscience and from the animal and human literature reviewed herein provides compelling support for the critical period hypothesis. Although it is not known with certainty why estrogen does not protect cognition and may even cause harm when administered to women over the age of 65years, it is likely that the events that characterize brain aging, such as a reduction in brain volume and in neuronal size, alterations in neurotransmitter systems, and a decrease in dendritic spine numbers, form an unfavorable background that precludes a neuroprotective effects of exogenous estrogen on the brain. Other factors that have likely contributed to the discrepancies in the estrogen-cognition literature include differences in the estrogen compounds used, their route of administration, cyclic versus continuous regimens, and the concomitant use of progestins. This critical analysis attempts to define conditions under which ET may protect aspects of cognition in aging women while also considering the cost/benefit ratio for the treatment of women aged 50-59years. Suggestions for specific future research questions are also addressed.

The clinical relevance of the relationship between estrogen and cognition in women

Randomized controlled trials (RCTs) and observational and longitudinal studies provide positive, albeit, inconsistent evidence that estrogen might protect against cognitive decline in postmenopausal women. The fact that the Women's Health Initiative Memory Study (WHIMS), the largest RCT to date, failed to find that estrogen therapy (ET) had a protective effect against cognitive aging led to the formulation of the critical period hypothesis which holds that ET will effectively protect against memory decline when it is initiated around the time of menopause but not when considerable time has elapsed since the menopause. Evidence from basic neuroscience, and from rodent, nonhuman primate, and human studies that supports this theory is presented. Although much work remains to be done on the timing of initiation of treatment, on the most effective hormonal compounds and on their routes of administration, the hope is that, eventually, hormonal treatments may be able to attenuate or prevent the decline in aspects of cognition that occur with normal aging.

Hot flashes and estrogen therapy do not influence cognition in early menopausal women

OBJECTIVE

To examine how menopausal symptoms and estrogen therapy (ET)-induced symptom relief affect cognition in early menopause.

DESIGN

There were two components. Part 1 was a cross-sectional study of 37 healthy, recently postmenopausal women with diverse menopausal symptoms. Women were categorized as having low (n=20) or high symptoms (n=17) based on a validated symptom questionnaire. Women completed mood and sleep questionnaires and underwent cognitive testing, which included verbal memory, visual memory, emotional memory, and verbal fluency. Thirty-two of these women went on to part 2 of the study. Fourteen were randomly assigned to receive ET and 18 to receive placebo for 8 weeks. Before treatment and at 4 and 8 weeks, women completed the same measures as in part 1 of the study.

RESULTS

High symptom women had more negative mood (P=0.01) and lower quality sleep (P<0.001) than low symptom women. Despite suffering from more menopausal symptoms, worse mood, and poorer sleep, women in the high symptom group performed the same on cognitive testing as women in the low symptom group. Women receiving ET had greater improvements in menopausal symptoms and sleep compared with those receiving the placebo (P<or=0.05). ET did not improve mood compared with placebo. Women receiving ET did not have any improvement in cognitive performance compared with those receiving the placebo.

CONCLUSIONS

Menopausal symptoms do not impair cognition. ET does not improve cognition despite alleviating symptoms and improving sleep in recently naturally menopausal women with diverse menopausal symptoms.

Hormone replacement therapy and cognitive performance in postmenopausal women—a review by cognitive domain

Laboratory, animal and neuroimaging evidences suggest that hormone replacement therapy (HRT) may be beneficial to human cognition. This systematic review includes 26 studies on the association between HRT and cognition and 17 studies on HRT and risk of dementia. It was hypothesised that HRT would have a positive association with cognitive speed and verbal memory and possibly visual memory but not with executive functioning, and would be associated with a decreased risk of dementia. Evidence for HRT's neuroenhancing and neuroprotective properties was also evaluated. There was significant statistical and clinical heterogeneity among studies precluding meta-analysis. Results showed no consistent relationship between HRT and performance in any cognitive domain. Cross-sectional studies tended to report more positive results than longitudinal studies and randomised-controlled trials, particularly in the areas of verbal memory and executive functioning. HRT was associated with decreased risk of dementia in observational studies, but with increased risk in one randomised-controlled trial. Cognitive improvement or maintenance are not secondary benefits of HRT.

Estrogen and cognitive aging in women

Although several randomized controlled trials of surgically menopausal women have provided evidence that estrogen protects aspects of memory, many cross-sectional and longitudinal studies, including those from the Women's Health Initiative Memory Study, have failed to confirm these findings. One critical difference between studies that found a protective effect of estrogen on memory and those that did not is that, in the former studies, treatment with estrogen began at the time of menopause and in the latter studies, it was first administered many years after the menopause had occurred. Recent evidence from rodent, nonhuman primate, and human studies consistently suggests that the timing of the initiation of estrogen treatment with regard to the menopause may be critical to our understanding of the estrogenic effect on memory. Results of these animal and human studies indicate that the initiation of estrogen treatment at the time of menopause, or soon after ovariectomy, provides a window of opportunity for the protection of memory in females whereas the administration of the hormone following a considerable delay in time after ovariectomy or following a natural menopause has little or no beneficial effect on cognition.

Age, hormones, and cognitive functioning among middle-aged and elderly men: cross-sectional evidence from the Massachusetts Male Aging Study

BACKGROUND

This study examines interrelationships among age, hormones, and cognition for middle-aged and elderly men, and tests whether hormones predict lower cognitive functioning and mediate the age-cognition relationship.

METHODS

We analyzed Time 2 data from the Massachusetts Male Aging Study, a population-based cohort study. Selection criteria included complete information on cognition and hormones (n = 981). Cognitive measures included working memory (Backward Digit Span test), speed/attention (Digit Symbol Substitution test), and spatial ability (Figural Relations test). Hormones included free testosterone, total testosterone, dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulfate (DHEAS), androstanediol glucuronide (3 alpha-A-diol-gluc), luteinizing hormone (LH), follicle-stimulating hormone (FSH), sex hormone-binding globulin (alternatively known as a "binding protein") (SHBG), prolactin (PRL), estrone (E1), and cortisol (CRT). Age was measured in years. Adjusted analyses added educational attainment, health conditions and behaviors, body mass index, and depression.

RESULTS

Older age was associated with lower cognitive functioning. In unadjusted models, logged free and total testosterone, DHEA, and DHEAS related to higher functioning in at least one cognitive domain; logged FSH, SHBG, and LH related to lower functioning in at least one cognitive domain; and logged E1, CRT, and PRL were not significant. In adjusted models, logged hormones did not relate to cognitive function except for logged E1 and CRT, which had negative effects. Logged hormones did not mediate the age-cognition relationship.

CONCLUSIONS

The direct effects of hormones on cognition are not significant when salient factors are considered. Further, hormones do not mediate the age-cognition relationship; it is necessary to look to other explanatory pathways.

Benefits and risks of sex hormone replacement in postmenopausal women

Because cardiovascular disease (CVD), which is far less common in young women than in men, but increases in prevalence in the postmenopausal years to that of men, estrogen repletion therapy (ERT) or combined hormone replacement therapy (HRT), has been widely used to protect against development of both CVD and osteoporosis, and possibly to delay or prevent cognitive loss or Alzheimer's disease (AD). To test the validity of favorable findings in many small-scale studies, and in clinical practice, a large-scale trial: the Women's Health Initiative (WHI) was undertaken by the National Institutes of Health (NIH), a trial that was prematurely ended because of increased CVD complications, despite some lessening of hip fractures. This paper suggests that the customary high intake of calcium (Ca)-advised to protect against osteoporosis, and the marginal magnesium (Mg) intake in the USA, might well be contributory to the adverse CV effects, that were all thromboembolic in nature. The procoagulant effect of estrogen is intensified by Ca; Mg-which counteracts many steps in the coagulation cascade and inhibits platelet aggregation and adhesion-is commonly consumed in sub-optimal amounts. The high American dietary Ca/Mg ratio might also be contributory to the WHI failure to confirm ERT's favorable mental effects. Discussed are mechanisms by which Mg enhances estrogen's central nervous system protective effects. Mg's improvement of cerebral blood flow, which improves brain metabolism, can also enhance removal of the beta amyloid peptide, accumulation of which is implicated in AD.

Histamine2 receptor antagonist use and decline in cognitive function among community dwelling elderly

PURPOSE

Previous studies have reported mixed results regarding the use of histamine(2) receptor antagonist use and cognitive function. This study evaluated the relationship between the use of histamine(2) receptor antagonists and cognitive decline among community dwelling elderly.

METHODS

This cohort study included 2082 subjects from the Duke Established Populations for Epidemiologic Studies of the Elderly who were not cognitively impaired at baseline (1989/90). Histamine(2) receptor antagonist use was determined during in-home interviews. Cognitive function was assessed at 3 and 7 years after baseline by two measures: (1) incident cognitive impairment defined by the short portable mental status questionnaire (SPMSQ); and (2) cognitive decline (increase in two or more SPMSQ errors). Analyzes used multivariable discrete-time hazard models with weighted data adjusted for sampling design and controlled for demographic, health behavior characteristics and health status.

RESULTS

At baseline, nearly 5% of participants used a histamine(2) receptor antagonist. During follow-up, incident cognitive impairment occurred in 24.0%, whereas 34.5% increased by two or more errors on the SPMSQ. In multivariable models, current histamine(2) receptor antagonist users compared to never users had a higher risk for cognitive impairment (Adj. RR 1.51; 95%CI 0.93-2.47) and for decline in performance (increase of two or more errors) on the SPMSQ (Adj. RR 1.24; 95%CI 0.74-2.08). A nonsignificant increased risk of cognitive impairment and decline with either higher dose or short-term use was found whereas a nonsignificant protective effect on cognitive decline with current long-term use was seen.

CONCLUSIONS

These results suggest no beneficial effects, and perhaps a detrimental effect, of histamine(2) receptor antagonist use on cognitive function in community dwelling elderly.

Cognitive Decline in High-Functioning Older Persons Is Associated with an Increased Risk of Hospitalization

OBJECTIVES

To examine hospital use for patients with evidence of cognitive decline indicative of early cognitive impairment.

DESIGN

Medicare Part A hospital utilization data were linked to data from the MacArthur Research Network on Successful Aging Community Study to examine the association between baseline cognition and decline in cognitive function over a 3-year period and any hospitalization over that same period.

SETTING

New Haven, Connecticut, and East Boston, Massachusetts.

PARTICIPANTS

Subjects (N=598) were from two sites of the MacArthur Research Network on Successful Aging Community Study, a 7-year cohort study of community-dwelling older persons with high physical and cognitive functioning.

MEASUREMENTS

Multivariate logistic regression was used to determine the association between any hospitalization over 3 years (1988-91) as the outcome variable and baseline cognitive function and decline in cognition over 3 years as primary predictor variables. Decline was based upon repeated (1988 and 1991) measures of delayed verbal recall and the Short Portable Mental Status Questionnaire (SPMSQ).

RESULTS

Of 598 subjects, 48 died between 1988 and 1991. No baseline (1988) delayed recall scores or change in recall scores (1988-91) were associated with hospitalization. Although 48.2% declined on verbal memory scores, decline was not associated with risk of hospitalization. Of 494 subjects with complete 3-year data, 31.2% declined at least one point on the SPMSQ, and 4.7% declined more than two points. Among individuals aged 75 and older at baseline, the adjusted odds ratio for hospitalization for those who declined more than 2 points compared with those who declined less was 7.8 (95% confidence interval=2.0-30.8).

CONCLUSION

Although specific memory tests were not associated with hospitalization, high-functioning older persons who experienced decline in overall cognitive function were more likely to be hospitalized. Variation in baseline cognitive function in this high-functioning cohort did not affect hospitalization, but additional research is needed to evaluate associations with other healthcare costs.

Dementia / Alzheimer's Disease

Health Issues

Dementia, including Alzheimer's disease (AD) increases exponentially with age from the age of 65. The number of people with dementia will increase significantly over the next three decades as the population ages. While prevalence and incidence rates do not differ markedly in women, compared to men, women live longer on average, so the number of women with dementia is greater than for men. Also, women are more frequently caregivers for people with dementia. Thus, dementia is an important health problem for women.

Key Findings

The Canadian Study of Health and Aging showed an increase in prevalence of dementia with age for both sexes, approximately doubling every five years of age. Rates of AD were higher in women whereas rates of vascular dementia were higher in men. The risk of AD increased with increasing age, lower education, and apolipoprotein E ε4. Regular physical activity was clearly protective in women; this was less clear for men. Use of non-steroidal anti-inflammatory drugs, wine consumption, and past exposure to vaccines decreased the risk of AD. Estrogen replacement therapy did not reduce the risk of AD. About three quarters of caregivers for dementia patients were women.

Data Gaps and Recommendations

The protective effect of regular physical activity for AD provides an additional reason to promote regular physical activity at all ages. Ongoing surveillance of the incidence, prevalence and risks for dementia is needed to monitor the impact of treatments as well as the aging of the population on the burden of dementia.

Estrogen treatment improves spatial learning in APP + PS1 mice but does not affect beta amyloid accumulation and plaque formation

We investigated the effects of ovariectomy (OVX) and 17 beta-estradiol (0.18 mg per pellet) treatment on spatial learning and memory, hippocampal beta amyloid (A beta) levels, and amyloid plaque counts in double transgenic mice (A/P) carrying mutated amyloid precursor protein (APPswe) and presenilin-1 (PS1-A246E). After OVX at 3 months of age, the mice received estrogen treatment for the last 3 months of their lifetime before they were killed at 6, 9, or 12 months of age. Estrogen treatment in A/P OVX mice increased the number of correct choices in a position discrimination task in the T-maze, and slightly improved their performance in a win-stay task (1/8 arms baited) in the radial arm maze (RAM). However, estrogen treatment did not reverse the A beta-dependent cognitive deficits of A/P mice in the water maze (WM) spatial navigation task. Furthermore, ovariectomy or estrogen treatment in OVX and sham-operated A/P mice had no effect on hippocampal amyloid accumulation. These results show that the estrogen treatment in a transgenic mouse model of Alzheimer's disease (AD) improves performance in the same learning and memory tasks as in the normal C57BL/6J mice. However, the estrogen effects in these mice appeared to be unrelated to A beta-induced cognitive deficits. Our results do not support the idea that estrogen treatment decreases the risk or alleviates the symptoms of Alzheimer's disease by inhibiting the accumulation of A beta or formation of amyloid plaques.

Elevated sex-hormone binding globulin in elderly women with Alzheimer’s disease

BACKGROUND

Hormone levels change significantly with increasing age. These changes may be related to, or be associated with, the emergence of age-related diseases, such as Alzheimer's disease (AD).

METHODS

Five hundred and seventy-six women over the age of 65 were studied from the Washington Heights-Inwood Columbia Aging Project (WHICAP). These women were selected from a group of healthy Medicare beneficiaries that were aged 65 and older living in the geographically defined area of northern Manhattan in New York City. Serum levels of estrone (E1), estradiol (E2), total testosterone (TT), dehydroepiandosterone (DHEA), luteinizing hormone (LH), follicle stimulating hormone (FSH), and sex-hormone binding globulin (SHBG) were measured.

RESULTS

Significant differences were found between patients with AD and controls only in the level of SHBG, which was 20% higher in patients compared to controls (68.5nmol/l versus 54.7nmol/l, P<0.001). We also estimated levels of total E2 because after menopause, E2 is largely derived from E1. AD patients had significantly lower levels of estimated E2 (AD 0.46 versus controls 0.49, P<0.01). Differences remained significant after adjusting for age, ethnic group, education, and body mass index (BMI).

CONCLUSIONS

A marked increase in SHBG levels was found in AD patients. SHBG normally responds to circulating testosterone and estrogen, therefore, elevated SHBG suggests an abnormal increase in its production and regulation. Further work is needed to clarify the cause and consequences of this observation.

Steroid hormones and neurosteroids in normal and pathological aging of the nervous system

Without medical progress, dementing diseases such as Alzheimer's disease will become one of the main causes of disability. Preventing or delaying them has thus become a real challenge for biomedical research. Steroids offer interesting therapeutical opportunities for promoting successful aging because of their pleiotropic effects in the nervous system: they regulate main neurotransmitter systems, promote the viability of neurons, play an important role in myelination and influence cognitive processes, in particular learning and memory. Preclinical research has provided evidence that the normally aging nervous system maintains some capacity for regeneration and that age-dependent changes in the nervous system and cognitive dysfunctions can be reversed to some extent by the administration of steroids. The aging nervous system also remains sensitive to the neuroprotective effects of steroids. In contrast to the large number of studies documenting beneficial effects of steroids on the nervous system in young and aged animals, the results from hormone replacement studies in the elderly are so far not conclusive. There is also little information concerning changes of steroid levels in the aging human brain. As steroids present in nervous tissues originate from the endocrine glands (steroid hormones) and from local synthesis (neurosteroids), changes in blood levels of steroids with age do not necessarily reflect changes in their brain levels. There is indeed strong evidence that neurosteroids are also synthesized in human brain and peripheral nerves. The development of a very sensitive and precise method for the analysis of steroids by gas chromatography/mass spectrometry (GC/MS) offers new possibilities for the study of neurosteroids. The concentrations of a range of neurosteroids have recently been measured in various brain regions of aged Alzheimer's disease patients and aged non-demented controls by GC/MS, providing reference values. In Alzheimer's patients, there was a general trend toward lower levels of neurosteroids in different brain regions, and neurosteroid levels were negatively correlated with two biochemical markers of Alzheimer's disease, the phosphorylated tau protein and the beta-amyloid peptides. The metabolism of dehydroepiandrosterone has also been analyzed for the first time in the aging brain from Alzheimer patients and non-demented controls. The conversion of dehydroepiandrosterone to Delta5-androstene-3beta,17beta-diol and to 7alpha-OH-dehydroepiandrosterone occurred in frontal cortex, hippocampus, amygdala, cerebellum and striatum of both Alzheimer's patients and controls. The formation of these metabolites within distinct brain regions negatively correlated with the density of beta-amyloid deposits.

Estrogen and cognitive functioning in women

Research in basic neuroscience has provided biological plausibility for the hypothesis that estrogen replacement therapy (ERT) would protect against cognitive aging in healthy women. The weight of the evidence from randomized controlled trials of estrogen and cognition in women shows that this hormone preferentially protects verbal memory in postmenopausal women, whereas findings from observational studies are less consistent and show a more diffuse effect of estrogen on a range of cognitive functions. There is fairly consistent evidence from epidemiological studies that ERT significantly reduces the risk of Alzheimer's disease (AD) in women. On the other hand, findings from controlled treatment trials of women diagnosed with probable AD failed to show that physiological doses of ERT ameliorate existing deficits in cognitive functioning and/or prevent further deterioration in memory that inevitably occurs in these women over time. Finally, an accumulating body of evidence is beginning to suggest that the immediate postmenopausal period may constitute a critical window for treatment with ERT that maximizes its potential to protect against cognitive decline with aging and/or to reduce the risk of AD.

The menopause and HRT. HRT and cognitive decline

It is biologically plausible that hormone replacement therapy (HRT) would be protective against cognitive decline and Alzheimer's disease (AD). We review observational and randomized trials to determine whether HRT might protect against cognitive decline in cognitively unimpaired and demented women. We also address issues of clinical relevance, including duration and type of treatment and patient characteristics, including type of menopause (surgical versus natural), age, education and menopausal symptoms. Differences in participant characteristics and testing methods limit the ability to draw conclusions across randomized studies of HRT in non-demented women. The available evidence suggests no detrimental effect of HRT on cognitive function and inconsistent benefits on verbal memory and reasoning, frontal functions and speeded attention. Meta-analyses of observational trials suggest that HRT protects against the development of AD, but randomized trials indicate no long-lasting benefit in patients with AD. Evidence is insufficient to recommend HRT to maintain cognitive function.

Cognitive and functional decline in adults aged 75 and older

OBJECTIVES

To simultaneously examine the influence of functional disability on the development of cognitive impairment and the influence of cognitive status on the development of functional disability over time and compare findings across ethnic groups.

DESIGN

A population-based longitudinal study.

SETTING

Galveston County, Texas.

PARTICIPANTS

Three hundred sixty-five community-dwelling Hispanic Americans, African Americans, and non-Hispanic whites, aged 75 and older.

MEASUREMENTS

Baseline measures included demographics, self-reported chronic medical conditions, functional disability, and cognitive status. Longitudinal measures included functional decline and cognitive decline.

RESULTS

Substantial functional decline was associated with each additional error on the mental status measure; substantial cognitive decline was associated with each additional antecedent disability. These findings were evident across all three ethnic groups, even when taking into account the effects of demographic factors and chronic health conditions, although the specific chronic health conditions that influenced cognitive and functional decline were found to vary across the three ethnic groups.

CONCLUSION

Our findings suggest that, rather than simply being correlated markers of increasing frailty, cognitive and functional decline appear to influence the development of one another. Clinicians need to be aware of these associations, which may affect the direction of preventive care and rehabilitation in the oldest old. Appropriate intervention may result in the prevention or delay of functional disability and cognitive decline. Awareness of the specific chronic health conditions that increase the risk for cognitive or functional decline in various ethnic groups, and the effect of comorbid disease, may also help efforts to prevent decline in older adults.

Is there a relationship between fat-free soft tissue mass and low cognitive function? Results from a study of 7,105 women

OBJECTIVES

To test the hypothesis that low fat-free soft tissue mass and cognitive impairment are independently associated.

DESIGN

Cross-sectional study.

SETTING

Five geographic areas of France.

PARTICIPANTS

Seven thousand one hundred five community-dwelling women aged 75 and older recruited from electoral rolls between 1992 and 1994.

MEASUREMENTS

Fat-free soft tissue mass, body fat mass, and bone mineral density were measured using dual-energy x-ray absorptiometry. Study participants were assessed for cognitive impairment using the Short Portable Mental Status Questionnaire and divided into two groups according to their scores. Logistic regression models were used to calculate multivariate-adjusted differences in body composition between two groups of subjects according to their cognitive function.

RESULTS

After adjustment for confounders, compared with women in the highest quartile of fat-free soft tissue mass, women in the lowest quartile had an odds ratio of 1.43 (95% confidence interval (CI) = 1.07-1.91) for cognitive impairment. Low fat mass was also associated with lower cognitive function, with an odds ratio of 1.35 (95% CI = 1.01-1.79) for the lower quartile of fat mass compared with the highest quartile. There was no association between cognitive impairment and bone mineral density.

CONCLUSIONS

This finding supports the hypothesis that low muscle mass is associated with cognitive impairment in older women. These two components represent major causes of frailty and functional decline in older people and could have some common mechanisms. Nevertheless, these results do not predict the causal variable.

Estrogen and cognitive aging in women

The steady increase in female life expectancy has attracted attention to the importance of preventing cognitive aging and Alzheimer's disease (AD) in women. Evidence from randomized, controlled trials and from cross-sectional and longitudinal studies shows that estrogen-replacement therapy preferentially protects against a decline in verbal memory in healthy postmenopausal women and decreases the risk of AD. Although results are not consistent across studies, they indicate that treatment with estrogen during the postmenopausal years might protect against cognitive aging in women during the latter part of their life.

Predicting cognitive impairment in high-functioning community-dwelling older persons: MacArthur Studies of Successful Aging

OBJECTIVES

To examine whether simple cognitive tests, when applied to cognitively intact older persons, are useful predictors of cognitive impairment 7 years later.

DESIGN

Cohort study.

SETTING

Durham, North Carolina; East Boston, Massachusetts; and New Haven, Connecticut, areas that are part of the National Institute on Aging Established Populations for Epidemiological Studies of the Elderly.

PARTICIPANTS

Participants, aged 70 to 79, from three community-based studies, who were in the top third of this age group, based on physical and cognitive functional status.

MEASUREMENTS

New onset of cognitive impairment as defined by a score of less than 7 on the Short Portable Mental Status Questionnaire (SPMSQ) in 1995.

RESULTS

At 7 years, 21.8% (149 of 684 subjects) scored lower than 7 on the SPMSQ. Using multivariate logistic regression, three baseline (1988) cognitive tests predicted impairment in 1995. These included two simple tests of delayed recall-the ability to remember up to six items from a short story and up to 18 words from recall of Boston Naming Test items. For each story item missed, the adjusted odds ratio (AOR) for cognitive impairment was 1.44 (95% confidence interval (CI) = 1.16-1.78, P <.001). For each missed item from the word list, the AOR was 1.20 (95% CI = 1.09-1.31, P <.001). The Delayed Recognition Span, which assesses nonverbal memory, also predicted cognitive impairment, albeit less strongly (odds ratio = 1.06 per each missed answer, 95% CI = 1.003-1.13, P =.04).

CONCLUSIONS

This study identifies measures of delayed recall and recognition as significant early predictors of subsequent cognitive decline in high-functioning older persons. Future efforts to identify those at greatest risk of cognitive impairment may benefit by including these measures.

The effects of estrogen replacement therapy on neuropsychological functioning in postmenopausal women with and without dementia: a critical and theoretical review

We review 42 studies examining the effects of estrogen replacement therapy (ERT) on memory and cognition in nondemented postmenopausal women. Although there are an appreciable number of nonsignificant findings, the number of significant findings favoring ERT users considerably outnumbers the rare findings of better performance in controls. Experimental studies demonstrate a consistent beneficial effect on verbal memory, but these are short-term studies of the more acute effects of ERT. The observational studies suggest that there may be a long-lasting effect of continued ERT on cognitive functioning, but these studies need to be interpreted with caution because of the lack of random assignment and a possible "healthy user bias." We also summarize findings from studies on the effects of ERT on Alzheimer's disease (AD). ERT is associated with a decreased risk for dementia, but there is little evidence for a positive effect on cognition in women with AD. Definitive answers to questions about the long-term effects of ERT on cognitive aging and risk of developing AD should be provided by 3 ongoing clinical trials.