Selective decline in memory function among healthy elderly

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.

Patient experience with a new teriparatide delivery device

OBJECTIVE

To determine functionality and acceptability of a new teriparatide (Forteo, Eli Lilly and Company, Indianapolis, IN, USA) delivery device by patients with osteoporosis.

RESEARCH DESIGN AND METHODS

This was an eight week, single-arm, multicenter, open-label clinical trial. Patients received teriparatide 20 microg/day by subcutaneous injection using a new delivery device. Men and postmenopausal women with osteoporosis at high risk for fracture were stratified to Current User (n = 92) or Not Current User (n = 107) groups. Current Users had used the original delivery device for > or =8 weeks, including uninterrupted use for four weeks before enrollment.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, NCT00577863.

MAIN OUTCOME MEASURES

The primary objective was to detect common complaints (> or =3% for all patients) regarding the functionality and acceptability of the new device. Complaints were categorized as functional (e.g., malfunction), nonfunctional (e.g., size), or user manual. Secondary objectives included questionnaire assessment of preference of the new versus original device, features of the new delivery device, and analysis of adverse events.

RESULTS

A total of 31 patients (16%) reported 47 complaints (four functional, 27 nonfunctional, and 16 user manual). There were two common complaints: device size (4.0%) and lack of information on alcohol swabs (3.5%). Overall, patients agreed that the new device was easy to use (99.5%), easy to learn to use (99%), easy to attach a needle (97%), easy to hold while injecting (95%), and that it reduced their reluctance to take injections (90%). Most Current Users (92%) preferred the new delivery device over the original device. Adverse events reported by > or =2% of patients were upper respiratory infection (3.5%), urinary tract infection (2%), influenza (2%), and headache (2%). Limitations include the one-arm study design and the short (eight week) duration of the study.

CONCLUSIONS

Patients found the new teriparatide delivery device easy to use and Current Users preferred the new delivery device over the original device.

Longitudinal modeling of age-related memory decline and the APOE epsilon4 effect

BACKGROUND

The APOE epsilon4 allele is associated with the risk of late-onset Alzheimer's disease. The age at which memory decline diverges among persons who are homozygous for the APOE epsilon4 allele, those who are heterozygous for the allele, and noncarriers is unknown.

METHODS

Using local advertisements, we recruited cognitively normal subjects between the ages of 21 and 97 years, who were grouped according to their APOE epsilon4 status. We then followed the subjects with longitudinal neuropsychological testing. Anyone in whom mild cognitive impairment or dementia developed during follow-up was excluded. We compared the rates of decline in predetermined cognitive measures between carriers and noncarriers of the APOE epsilon4 allele, using a mixed model for longitudinal change with age.

RESULTS

We analyzed 815 subjects: 317 APOE epsilon4 carriers (79 who were homozygous for the APOE epsilon4 allele and 238 who were heterozygous) and 498 noncarriers. Carriers, as compared with noncarriers, were generally younger (mean age, 58.0 vs. 61.4 years; P<0.001) and were followed for a longer period (5.3 vs. 4.7 years, P=0.01), with an equivalent duration of formal education (15.4 years) and proportion of women (69%). Longitudinal decline in memory in carriers began before the age of 60 years and showed greater acceleration than in noncarriers (P=0.03), with a possible allele-dose effect (P=0.008). We observed similar although weaker effects on measures of visuospatial awareness and general mental status.

CONCLUSIONS

Age-related memory decline in APOE epsilon4 carriers diverges from that of noncarriers before the age of 60 years, despite ongoing normal clinical status.

Hypertension and cognitive decline in rural elderly Chinese

OBJECTIVES

To examine the association between hypertension and cognitive decline in older adults.

DESIGN

Prospective observational study.

SETTING

Four rural counties in China.

PARTICIPANTS

Two thousand rural Chinese aged 65 and older (median age 70, range 65-92) participated in a baseline evaluation. A follow-up evaluation of 1,737 subjects was conducted 2.5 years after baseline.

MEASUREMENTS

Cognitive function was assessed using the Community Screening Instrument for Dementia (CSID), Consortium to Establish a Registry for Alzheimer's Disease (CERAD) Word List Learning and Recall Tests, Indiana University (IU) Story Recall Test, Animal Fluency Test, and IU Token Test. Hypertension was defined as the mean of two readings of systolic blood pressure (BP) of 140 mmHg or greater, diastolic BP of 90 mmHg or greater, or according to self-report. Cognitive decline was derived as the difference between baseline and follow-up scores. Analysis of covariance models were used to estimate the association between hypertension, BP, and cognitive decline, adjusting for other covariates.

RESULTS

Greater decline was found on the CERAD 10-Word List Learning (P<.001) and Recall (P=.01) scores for subjects with hypertension than for those without. In particular, significantly greater decline was seen in the group with hypertension that was not taking medication than in the group without hypertension. No significant difference on cognitive decline was found between subjects with hypertension who were taking medication and those without hypertension.

CONCLUSION

Untreated hypertension was associated with greater cognitive decline in this Chinese cohort. Better hypertension detection and treatment in elderly people, especially in developing countries, may offer protection against cognitive decline.

Episodic memory loss is related to hippocampal-mediated beta-amyloid deposition in elderly subjects

Although beta-amyloid (Abeta) plaques are a primary diagnostic criterion for Alzheimer's disease, this pathology is commonly observed in the brains of non-demented older individuals. To explore the importance of this pathology in the absence of dementia, we compared levels of amyloid deposition (via 'Pittsburgh Compound-B' (PIB) positron emission tomography (PET) imaging) to hippocampus volume (HV) and episodic memory (EM) in three groups: (i) normal controls (NC) from the Berkeley Aging Cohort (BAC NC, n = 20); (ii) normal controls (NC) from the Alzheimer's disease neuroimaging initiative (ADNI NC, n = 17); and (iii) PIB+ mild cognitive impairment subjects from the ADNI (ADNI PIB+ MCI, n = 39). Age, gender and education were controlled for in each statistical model, and HV was adjusted for intracranial volume (aHV). In BAC NC, elevated PIB uptake was significantly associated with smaller aHV (P = 0.0016) and worse EM (P = 0.0086). Within ADNI NC, elevated PIB uptake was significantly associated with smaller aHV (P = 0.047) but not EM (P = 0.60); within ADNI PIB+ MCI, elevated PIB uptake was significantly associated with both smaller aHV (P = 0.00070) and worse EM (P = 0.046). To further understand these relationships, a recursive regression procedure was conducted within all ADNI NC and PIB+ MCI subjects (n = 56) to test the hypothesis that HV mediates the relationship between Abeta and EM. Significant correlations were found between PIB index and EM (P = 0.0044), PIB index and aHV (P < 0.0001), as well as between aHV and EM (P < 0.0001). When both aHV and PIB were included in the same model to predict EM, aHV remained significant (P = 0.0015) whereas PIB index was no longer significantly associated with EM (P = 0.50). These results are consistent with a model in which Abeta deposition, hippocampal atrophy, and EM occur sequentially in elderly subjects, with Abeta deposition as the primary event in this cascade. This pattern suggests that declining EM in older individuals may be caused by Abeta-induced hippocampus atrophy.

Estrous cycle, pregnancy, and parity enhance performance of rats in object recognition or object placement tasks

Ovarian hormone elevations are associated with enhanced learning/memory. During behavioral estrus or pregnancy, progestins, such as progesterone (P(4)) and its metabolite 5 alpha-pregnan-3 alpha-ol-20-one (3 alpha,5 alpha-THP), are elevated due, in part, to corpora luteal and placental secretion. During 'pseudopregnancy', the induction of corpora luteal functioning results in a hormonal milieu analogous to pregnancy, which ceases after about 12 days, due to the lack of placental formation. Multiparity is also associated with enhanced learning/memory, perhaps due to prior steroid exposure during pregnancy. Given evidence that progestins and/or parity may influence cognition, we investigated how natural alterations in the progestin milieu influence cognitive performance. In Experiment 1, virgin rats (nulliparous) or rats with two prior pregnancies (multiparous) were assessed on the object placement and recognition tasks, when in high-estrogen/P(4) (behavioral estrus) or low-estrogen/P(4) (diestrus) phases of the estrous cycle. In Experiment 2, primiparous or multiparous rats were tested in the object placement and recognition tasks when not pregnant, pseudopregnant, or pregnant (between gestational days (GDs) 6 and 12). In Experiment 3, pregnant primiparous or multiparous rats were assessed daily in the object placement or recognition tasks. Females in natural states associated with higher endogenous progestins (behavioral estrus, pregnancy, multiparity) outperformed rats in low progestin states (diestrus, non-pregnancy, nulliparity) on the object placement and recognition tasks. In earlier pregnancy, multiparous, compared with primiparous, rats had a lower corticosterone, but higher estrogen levels, concomitant with better object placement performance. From GD 13 until post partum, primiparous rats had higher 3 alpha,5 alpha-THP levels and improved object placement performance compared with multiparous rats.

Memory complaints in healthy young and elderly adults: reliability of memory reporting

The relationship between memory complaints and objective memory performance remains poorly understood, particularly in young and middle aged people. We studied the relationship between reports of memory complaints and objective memory performance, and the possibility of differentiating good and poor reporters across the lifespan based on concordance between reported abilities and objectively assessed performance. This cross-sectional study enrolled 292 healthy individuals, aged 18 to 87 years, able to perform common activities of daily living and without neurological or psychiatric conditions or systemic diseases likely to interfere with cognition. No correlation between memory complaints, as assessed by the Subjective Memory Complaints scale (SMC) score and the objective memory performance, evaluated by the long-delay free recall (LDFR) score of the California Verbal Learning Test (CVLT), was found, even when grouping the participants by decade. The SMC score was influenced by the presence of depressive symptoms. Participants who were more educated, female and younger tended to have a higher CVLT-LDFR score. Younger subjects were more likely to have good memory performance and report few memory complaints than older subjects. In conclusion, there are differences in the reliability of memory reporting across the lifespan, younger subjects being more likely to correctly report good memory than older subjects.

A survey of attitudes of clinicians towards the diagnosis and treatment of mild cognitive impairment in Australia and New Zealand

OBJECTIVES

The aim of the study was to assess the attitudes of clinicians to the diagnostic construct of mild cognitive impairment (MCI), their approach to relaying the diagnosis to patients and families, and recommended treatment and follow-up.

METHOD

An anonymous questionnaire was sent out to 503 members of the Australian Society for Geriatric Medicine (ASGM) and New Zealand Geriatrics Society (NZGS), of whom 163 replied.

RESULTS

Most responders (83%) had diagnosed MCI. About 70% rated the importance of separating MCI from dementia, or MCI from normal cognition, as 4 or 5 on a scale from 1 (not very important) to 5 (very important). Most responders reported that they would inform their patients and families of a diagnosis of MCI, and used that term. A minority used the term "early Alzheimer's disease," but 44% of NZGS members used other terms to relay the diagnosis compared to 13% of ASGM members. Follow-up was most often recommended at 6-12 months. Non-pharmacological treatment (such as mental stimulation strategies) was recommended most often, followed by no treatment.

CONCLUSIONS

The diagnostic entity of MCI appears to have a general acceptance among those who responded to the survey, and the term has gained use in clinical practice. Most clinicians are recommending follow-up, recognizing the high risk for progression. Treatment recommendations do not favor pharmaceuticals, reflecting the current evidence for lack of effect.

A randomized, two-year study of the efficacy of cognitive intervention on elderly people: the Donostia Longitudinal Study

BACKGROUND

Research on non-pharmacological therapies (cognitive rehabilitation) in old age has been very limited, and most has not considered the effect of interventions of this type over extended periods of time.

OBJECTIVE

To investigate a new cognitive therapy in a randomized study with elderly people who did not suffer cognitive impairment.

METHODS

The efficacy of this therapy was evaluated by means of post-hoc analysis of 238 people using biomedical, cognitive, behavioural, quality of life (QoL), subjective memory, and affective assessments.

RESULTS

Scores for learning potential and different types of memory (working memory, immediate memory, logic memory) for the treatment group improved significantly relative to the untreated controls.

CONCLUSIONS

The most significant finding in this study was that learning potential continued at enhanced levels in trained subjects over an intervention period lasting two years, thereby increasing rehabilitation potential and contributing to successful ageing.

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.

Cognitive profiles of aging and aging-related conditions

This review presents some of the current research and thinking regarding the neuropsychological features associated with aging and aging-related conditions. In the context of the current longevity revolution, many older adults are increasingly concerned about their cognitive performance and the risk for cognitive decline. This makes it critically important to understand the neuropsychological profiles of normal aging and the cognitive features of conditions associated with aging, such as age-associated memory impairment, mild cognitive impairment and dementia. There are also several factors that can modify the neuropsychological abilities and outcomes associated with aging, including gender, genetic status, lifestyle issues and education. The authors point to the importance for future research to embrace a fluid or multifactorial approach to neuropsychology, to focus on those factors contributing to healthy cognition and successful aging, and to correlate neuropsychological changes with the results of neuroimaging.

What's behind the decline? The role of white matter in brain aging

The specific molecular events that underlie the age-related loss of cognitive function are poorly understood. Although not experimentally substantiated, age-dependent neuronal loss has long been considered central to age-related cognitive decline. More recently, age-related changes in brain white matter have taken precedence in explaining the steady decline in cognitive domains seen in non-diseased elderly. Characteristic alterations in the ultrastructure of myelin coupled with evidence of inflammatory processes present in the white matter of several different species suggest that specific molecular events within brain white matter may better explain observed pathological changes and cognitive deficits. This review focuses on recent evidence highlighting the importance of white matter in deciphering the course of "normal" brain aging.

An in vivo correlate of exercise-induced neurogenesis in the adult dentate gyrus

With continued debate over the functional significance of adult neurogenesis, identifying an in vivo correlate of neurogenesis has become an important goal. Here we rely on the coupling between neurogenesis and angiogenesis and test whether MRI measurements of cerebral blood volume (CBV) provide an imaging correlate of neurogenesis. First, we used an MRI approach to generate CBV maps over time in the hippocampal formation of exercising mice. Among all hippocampal subregions, exercise was found to have a primary effect on dentate gyrus CBV, the only subregion that supports adult neurogenesis. Moreover, exercise-induced increases in dentate gyrus CBV were found to correlate with postmortem measurements of neurogenesis. Second, using similar MRI technologies, we generated CBV maps over time in the hippocampal formation of exercising humans. As in mice, exercise was found to have a primary effect on dentate gyrus CBV, and the CBV changes were found to selectively correlate with cardiopulmonary and cognitive function. Taken together, these findings show that dentate gyrus CBV provides an imaging correlate of exercise-induced neurogenesis and that exercise differentially targets the dentate gyrus, a hippocampal subregion important for memory and implicated in cognitive aging.

Relation between vascular risk factors and neuropsychological test performance among elderly persons with Alzheimer's disease

BACKGROUND

Vascular risk factors increase the risk of Alzheimer's disease (AD). The mechanisms for these associations are unclear, and may be due to misdiagnosis of a vascular dementia syndrome as AD.

OBJECTIVE

To examine differences in neuropsychological profile among persons diagnosed clinically with AD with and without vascular risk factors or stroke.

METHODS

Community based cohort study. Individual and composite scores of neuropsychological tests at the time of clinical diagnosis of incident AD were compared among 243 persons with and without vascular risk factors or stroke.

RESULTS

Among subjects with incident AD, diabetes was associated with lower performance in Delayed Recall of the Selective Reminding Test (SRT), while persons diagnosed with hypertension scored lower in consistent long term recall (CLTR) of the SRT and current smokers scored lower in Category Fluency. None of the risk factors was associated with differences in composite scores in memory, abstract/visuospatial or language domain, nor was the number of risk factors per person. Persons with stroke had a higher delayed recall score at the time of AD diagnosis.

CONCLUSION

The presence of vascular risk factors among persons with clinically diagnosed AD was associated with subtle differences in neuropsychological profile at the time of diagnosis. This study needs to be replicated in samples with brain imaging, a comprehensive executive abilities battery, and pathological diagnosis of AD.

The critical period hypothesis: can it explain discrepancies in the oestrogen-cognition literature?

Although there is compelling evidence from small randomised controlled trials and cross-sectional studies indicating that oestrogen helps to protect against cognitive ageing in women, the findings of the large, Women's Health Initiative Memory Study failed to support the earlier findings. The attempt to resolve these discrepancies led to the formulation of the Critical Period Hypothesis which holds that oestrogen has maximal protective benefits on cognition in women when it is initiated closely in time to a natural or surgical menopause but not when treatment is begun decades after the menopause. This article reviews the evidence from basic neuroendocrinology, from animal behavioural studies and from human studies that supports the critical period hypothesis. In view of the promise of this hypothesis and its considerable clinical implications, a direct test of its validity is warranted.

Alzheimer's Quick Test cognitive screening criteria for West African speakers of Krio

OBJECTIVES

To obtain normative data for Alzheimer's Quick Test (AQT) measures of perceptual and cognitive speed from West African speakers of Krio.

SUBJECTS

Normal adults, who were functionally independent, from Sierra Leone (n = 164) aged 25-79 years.

METHODS

Perceptual and cognitive speed were measured with AQT single- and dual-dimension colour-number (C-N) and colour-animal (C-A) naming tasks. Tests were administered individually in the participants' communities.

RESULTS

Men and women performed similarly (P>0.05), whereas literate speakers used significantly less time than preliterate peers (P<0.01). Correlations between age and colour naming were low (P<0.01) and speed decreased by <0.1 s per year. Dual-dimension naming remained stable across ages. Correlations with years of education were low for dual-dimension naming (P<0.01) and speed increased approximately 0.4 s per added year. Correlations between age and education and AQT naming were non-significant for literate participants. Criterion time cut-offs (seconds) for screening were developed for preliterate and literate speakers of Krio for typical (<+1 SD), slower-than-typical (between +1 and +2 SD) and atypical (>+2 SD) performance.

CONCLUSION

AQT C-N and C-A naming are time efficient (3-5 min each), objective and reliable and can be administered in Krio to West African adults in Africa, Europe or North America to screen for cognitive impairments and facilitate referral for medical workup.

Functions of the mirror neuron system: implications for neurorehabilitation

Mirror neurons discharge during the execution of hand object-directed actions and during the observation of the same actions performed by other individuals. These neurons were first identified in the ventral premotor cortex (area F5) and later on in the inferior parietal lobule of monkey brain, thus constituting the mirror neuron system. More recently, mirror neurons for mouth object-directed actions have also been found in the monkey. Several pieces of experimental data demonstrate that a mirror neuron system devoted to hand, mouth, and foot actions is also present in humans. In the present paper we review the experimental evidence on the role of the mirror neuron system in action understanding, imitation learning of novel complex actions, and internal rehearsal (motor imagery) of actions. On the basis of features of the mirror neuron system and its role in action understanding and imitation, we discuss the possible use of action observation and imitation as an approach for systematic training in the rehabilitation of patients with motor impairment of the upper limb after stroke.

Biological markers of age-related memory deficits: treatment of senescent physiology

In humans, age-related memory impairments begin in mid-life and cognitive weakening continues with advancing age. An important aspect of defining memory decline is the distinction between dementia as a result of neurological diseases, such as Alzheimer's disease, and memory loss not specifically associated with disease. Within the population of elderly without dementia, there is considerable variability in memory. This variability is likely to be a result of the interaction of genetic make-up and environment, which influences several processes for cell maintenance and repair including oxidative damage and cholesterol metabolism, leading to disruption of Ca(2+) homeostasis, and ultimately Ca(2+)-dependent processes that underlie memory. In humans, several methods have been employed to distinguish biological markers of aging that may predict cognitive decline. Memory deficits associated with normal aging and Alzheimer's disease have been linked to a decrease in the volume of brain structures, such as the hippocampus and to genetic markers, such as apolipoprotein E. In this regard, examination of CSF for biomarkers of disease can help in differentiating normal aging from Alzheimer's disease. Measures of oxidative stress and cholesterol in plasma correlate with memory deficits; research suggests that treatments that reduce oxidative stress or cholesterol through exercise, diet or the use of antioxidant vitamins may delay cognitive decline.Nevertheless, to date, very little treatment is available to reverse memory deficits in later life. In this regard it is important to identify individuals at risk for memory deficits in order to discriminate different mechanisms of brain aging and develop treatments. Considerable effort is driving research to develop accurate biological markers of brain aging. In turn, these markers will provide information on mechanisms of aging and cognitive decline and point to potential treatments. Accordingly, the effectiveness of treatment needs to be verified for both cognitive changes and biological markers that are specific for age-related memory deficits.

Traumatic brain injury in the elderly: diagnostic and treatment challenges

The purpose of this review is to introduce geriatric practitioners to issues and challenges presented in the elderly after onset of traumatic brain injury (TBI). Issues discussed include the magnitude of TBI in the elderly, mechanisms of onset, issues specific to both acute and rehabilitation care for the elderly with TBI, and specific physical and behavioral manifestations of TBI that may need to be addressed on an inpatient or outpatient basis. General guidelines are provided for the diagnosis and treatment of older individuals who have TBI, with specific clinical scenarios illustrating key points.

Frontopolar cortex mediates abstract integration in analogy

Integration of abstractly similar relations during analogical reasoning was investigated using functional magnetic resonance imaging. Activation elicited by an analogical reasoning task that required both complex working memory and integration of abstractly similar relations was compared to activation elicited by a non-analogical task that required complex working memory in the absence of abstract relational integration. A left-sided region of the frontal pole of the brain (BA 9/10) was selectively active for the abstract relational integration component of analogical reasoning. Analogical reasoning also engaged a left-sided network of parieto-frontal regions. Activity in this network during analogical reasoning is hypothesized to reflect categorical alignment of individual component terms that make up analogies. This parieto-frontal network was also engaged by the complex control task, which involved explicit categorization, but not by a simpler control task, which did not involve categorization. We hypothesize that frontopolar cortex mediates abstract relational integration in complex reasoning while parieto-frontal regions mediate working memory processes, including manipulation of terms for the purpose of categorical alignment, that facilitate this integration.

Stroke and memory performance in elderly persons without dementia

BACKGROUND

There are conflicting data showing that stroke is associated with a higher risk of dementia and a more severe decline in persons with cognitive impairment. However, it remains unclear if cerebrovascular disease is directly related to cognitive decline in the absence of cognitive impairment or dementia.

OBJECTIVE

To examine the association between stroke and changes in cognitive function over time in elderly persons without dementia at baseline.

DESIGN

The results of neuropsychological tests from several intervals over a 5-year period were clustered into domains of memory, abstract/visuospatial, and language in 1271 elderly persons without dementia or cognitive decline. Stroke was related to the slope of performance in each cognitive domain using generalized estimating equations.

RESULTS

Memory performance declined over time, while abstract/visuospatial and language performance remained stable during the study period. Stroke was associated with a more rapid decline in memory performance, while there was no association between stroke and decline in abstract/visuospatial or language performance. The association between stroke and decline in memory performance was strongest for men and for persons without an APOEepsilon4 allele. A significant association between stroke and decline in abstract/visuospatial performance was also observed for persons without the APOEepsilon4 allele.

CONCLUSION

A history of stroke is related to a progressive decline in memory and abstract/visuospatial performance, especially among men and those without an APOEepsilon4 allele.

Longitudinal changes during aging using proton magnetic resonance spectroscopy

OBJECTIVE

We aimed to examine the longitudinal change in proton magnetic resonance spectroscopy ((1)H-MRS) visible metabolites (N-acetyl aspartate [NAA], creatine [Cr], choline [Cho], and myo-Inositol [mI]) in brains of elderly individuals over 3 years and relate them to cognitive function.

METHODS

Neurologically and psychiatrically normal volunteers (n = 40) were examined at baseline and 3 years later with (1)H-MRS in two voxels (frontal white matter n = 29, and occipitoparietal gray matter n = 36) and with detailed neuropsychological assessments. Longitudinal analyses were performed with age, educational level, sex, and white matter hyperintensities (WMH) in voxels as covariates.

RESULTS

Frontal mI was significantly increased over time in male participants, but all other metabolites were stable over time. Neuropsychological performance was not significantly changed over 3 years, and there was no relationship between change in metabolite levels and change in neuropsychological function.

CONCLUSIONS

MRS-visible metabolites are stable in elderly persons over 3 years, with the exception of mI which shows an increase. Increasing mI may be a marker of aging or a preclinical neurodegenerative process. MRS changes do not correlate with change in neurocognitive function during aging.

Effect of smoking and time on cognitive function in the elderly without dementia

OBJECTIVE

To examine the association between smoking and changes in cognitive function over time in elderly persons without dementia.

METHODS

The results of neuropsychological tests grouped into domains of memory, abstract-visuospatial, and language, from several intervals over a 5-year period in 791 elderly patients without dementia or cognitive impairment. Smoking history was categorized as never, current, or past smokers and related to the slope of performance in each cognitive domain using generalized estimating equations.

RESULTS

Performance in all cognitive domains declined over time. Memory performance declined more rapidly among current smokers aged >75 years than in nonsmokers similar in age, including those who never smoked or had quit smoking. The effect was stronger among those without an APOE-epsilon4 allele. There was no association between smoking and performance in any cognitive domain in persons aged <75 years, and there was no association between past smoking and performance on any of the three cognitive factors at any time interval in either age group.

CONCLUSION

Current smokers aged >75 years perform more poorly on cognitive tests and appear to decline in memory more rapidly than their peers who do not smoke, especially if they lack the APOE-epsilon4 allele. Smoking does not affect cognitive performance in those persons aged <75 years.

Demographic Factors Influence Cognitive Recovery After Shunt for Normal-Pressure Hydrocephalus

BACKGROUND

Several studies have reported that ventriculoperitoneal shunt insertion for treatment of normal-pressure hydrocephalus results in improvement of gait and, less frequently, improvement of cognition. We sought to identify the demographic factors associated with cognitive improvement after shunt insertion to improve assessment of prognosis for cognitive gains with treatment.

REVIEW SUMMARY

We report cognitive testing before and after ventriculoperitoneal shunt insertion in 36 patients with normal pressure hydrocephalus, who previously had improvement of any clinical symptom--gait, urinary incontinence, cognition--after a diagnostic trial of continuous cerebrospinal fluid drainage.

CONCLUSIONS

One third of patients met our definition of good cognitive improvement: improvement by at least 25% on at least half of the cognitive tests administered. There was a significant negative linear relationship between age and probability of good cognitive improvement. Additionally, the degree of cognitive improvement was found to be greater in women than men (P = 0.002). Age was found to be a better predictor of improvement on memory tests, while sex was a better predictor of improvement on non-memory tests after shunt insertion.

Neuropsychology in Alzheimer's disease and other dementia research

PURPOSE OF REVIEW

This review describes a variety of neuropsychological dementia studies published between January 2004 and June 2005. In selecting articles for description in the present paper, our goal was not a comprehensive review of what is an enormous and growing literature, but rather to select and describe individual interesting studies from a sufficient range of dementia-related topics to permit illustration of some of the important questions for which a neuropsychological perspective aids in the understanding of dementias.

RECENT FINDINGS

Findings in the studies reviewed include a variety of different topics. Some of the themes include the following: (a) Alzheimer's disease is the most common cause of dementia, but a large body of research documents that there are important cognitive differences among various types of dementia, (b) the emerging research is also important in demonstrating the need for more sensitive clinical screening measures, (c) cognitive data are strongly predictive of functional decline, and (d) subtle declines in verbal learning appear to precede clinical Alzheimer's disease.

SUMMARY

Neuropsychological data are key to progress in understanding and developing more effective treatments for Alzheimer's disease and other dementia. For instance, efforts to identify early markers of dementia will be a key component to development of early intervention strategies.

Cognitive aging and Alzheimer's disease

Cognitive aging and clinically probable Alzheimer's disease can be discriminated by means of clinical and neuropsychological testing, and structural and functional imaging techniques. Research at the level of cognitive brain systems and at the molecular level provides exciting new insights into the relation between aging and neurodegeneration. The advances at the clinical and at the basic research levels are necessary if we wish to meet the formidable challenge that the increasing prevalence of Alzheimer's disease poses to the medical community.

A longitudinal study of implicit and explicit memory in old persons

Decline in explicit memory with advancing age is a common finding, but it is unclear whether implicit memory (repetition priming) declines or remains stable. Meta-analyses of studies that examined differences between extreme groups (young-old), typically at a single point in time and on a single test, suggest that a mild reduction in priming occurs with advancing age. The authors examined explicit memory and priming, on multiple tests over 4 annual data-collection waves, in a large group of older persons without dementia at baseline. Explicit memory declined significantly, but priming remained stable. Findings indicate that explicit memory and priming are dissociable on the basis of age-related change and that mildly reduced priming is not an inevitable consequence of growing older.

Age-related functional changes of prefrontal cortex in long-term memory: a repetitive transcranial magnetic stimulation study

Neuroimaging findings suggest that the lateralization of prefrontal cortex activation associated with episodic memory performance is reduced by aging. It is still a matter of debate whether this loss of asymmetry during encoding and retrieval reflects compensatory mechanisms or de-differentiation processes. We addressed this issue by the transient interference produced by repetitive transcranial magnetic stimulation (rTMS), which directly assesses causal relationships between performance and stimulated regions. We compared the effects of rTMS (a rapid-rate train occurring simultaneously to the presentation of memoranda) applied to the left or right dorsolateral prefrontal cortex (DLPFC) on visuospatial recognition memory in 66 healthy subjects divided in two classes of age (<45 and >50 years). In young subjects, rTMS of the right DLPFC interfered with retrieval more than left DLPFC stimulation. The asymmetry of the effect progressively vanished with aging, as indicated by bilateral interference effects on recognition performance. Conversely, the predominance of left DLPFC effect during encoding was not abolished in elders, thus probing its causal role for encoding along the life span. Findings confirm that the neural correlates of retrieval modify along aging, suggesting that the bilateral engagement of the DLPFC has a compensatory role on the elders' episodic memory performance.

Hippocampal and neocortical activation during repetitive encoding in older persons

Episodic memory function is known to decline in the course of normal aging; however, compensatory techniques can improve performance significantly in older persons. We investigated the effects of the memory enhancing technique of repetition encoding on brain activation using event-related functional magnetic resonance imaging (fMRI). Twelve healthy older adults without cognitive impairment were studied with fMRI during repetitive encoding of face-name pairs. During the first encoding trials of face-name pairs that were subsequently remembered correctly, activation of the hippocampus and multiple neocortical regions, including prefrontal, parietal and fusiform cortices, was observed. The second and third encoding trials resulted in continued activation in neocortical regions, but no task-related response within the hippocampus. Functional imaging of successful memory processes thus permits us to detect regionally specific responses in the aging brain. Our findings suggest that hippocampal function is preserved in normal aging and that repetition-based memory enhancing techniques may engage primarily neocortical attentional networks.

Education modifies the effect of apolipoprotein epsilon 4 on cognitive decline

OBJECTIVES

To assess the influence of education on the association between apolipoprotein E and cognitive change.

DESIGN

Prospective cohort.

PARTICIPANTS

HMO-based sample of 2168 non-demented community-dwelling elderly followed over 6 years.

MEASUREMENTS

Generalized estimating equations were used with the difference between baseline and follow-up cognitive abilities screening instrument (CASI) as the outcome variable.

RESULTS

At follow-up, 6% of the sample had a decline of 1.5 S.D. or greater on the CASI. Compared to individuals without an APOE4 allele, individuals with a single APOE4 allele did not have greater CASI decline. By contrast, individuals with two APOE4 alleles experienced greater decline in cognitive performance and the magnitude of that decline decreased as years of educational attainment increased. These relationships held after adjusting for age, gender, ethnicity, depression, diabetes, and history of vascular disease.

CONCLUSION

Lower education was associated with steep 4-year cognitive decline for APOE4 homozygotes but not for APOE4 heterozygotes. Potentially modifiable host factors such as education could influence the association of high-risk genotypes and cognitive decline.

Age-associated cognitive deficits in humans and dogs: a comparative neuropsychological approach

We compared performance of younger and older human participants to that of younger and older dogs on tasks that evaluate object discrimination, egocentric spatial ability, object recognition, spatial memory, and cognitive flexibility. Our goal was to determine whether (i) tasks sensitive to advanced age in dogs are also age-sensitive in humans; (ii) the pattern of task difficulty observed in dogs mirrors that observed in humans; (iii) dogs and humans use similar strategies to solve equivalent tasks. Dogs performed more poorly than humans on reversal tasks that evaluate cognitive flexibility. We suggest that dogs, most notably older dogs, use different strategies than healthy humans when solving these tasks. Humans appear to test a priori hypotheses to solve the task at hand. As a consequence, expectations about the complexity of the task being tested can impair human performance. By contrast, dogs appear to rely more heavily on either simpler hypotheses, or associative trial and error learning, which probably accounts for their difficulty in learning non-matching tasks. Dogs also show perseverative responding, which hinders the acquisition of reversal tasks.

Age does not increase rate of forgetting over weeks--neuroanatomical volumes and visual memory across the adult life-span

The aim of the study was to investigate whether age affects visual memory retention across extended time intervals. In addition, we wanted to study how memory capabilities across different time intervals are related to the volume of different neuroanatomical structures (right hippocampus, right cortex, right white matter). One test of recognition (CVMT) and one test of recall (Rey-Osterrieth Complex Figure Test) were administered, giving measures of immediate recognition/recall, 20-30 min recognition/recall, and recognition/recall at a mean of 75 days. Volumetric measures of right hemisphere hippocampus, cortex, and white matter were obtained through an automated labelling procedure of MRI recordings. Results did not demonstrate a steeper rate of forgetting for older participants when the retention intervals were increased, indicating that older people have spared ability to retain information in the long-term store. Differences in neuroanatomical volumes could explain up to 36% of the variance in memory performance, but were not significantly related to rates of forgetting. Cortical volume and hippocampal volume were in some cases independent as predictors of memory function. Generally, cortical volume was a better predictor of recognition memory than hippocampal volume, while the 2 structures did not differ in their predictive power of recall abilities. While neuroanatomical volumetric differences can explain some of the differences in memory functioning between younger and older persons, the hippocampus does not seem to be unique in this respect.

Quantitative Genetic Analysis of Latent Growth Curve Models of Cognitive Abilities in Adulthood

Though many cognitive abilities exhibit marked decline over the adult years, individual differences in rates of change have been observed. In the current study, biometrical latent growth models were used to examine sources of variability for ability level (intercept) and change (linear and quadratic effects) for verbal, fluid, memory, and perceptual speed abilities in the Swedish Adoption/Twin Study of Aging. Genetic influences were more important for ability level at age 65 and quadratic change than for linear slope at age 65. Expected variance components indicated decreasing genetic and increasing nonshared environmental variation over age. Exceptions included one verbal and two memory measures that showed increasing genetic and nonshared environmental variance. The present findings provide support for theories of the increasing influence of the environment with age on cognitive abilities.

The relationship between type 2 diabetes and cognitive dysfunction: longitudinal studies and their methodological limitations

Type 2 diabetes and dementia in the elderly are major public health problems. Cross-sectional studies have suggested that these two conditions may be inter-related, but the nature of this association is uncertain. Causation can only be established through studies with a longitudinal design, taking into account the many potential confounding factors in any study of cognition. A literature search has identified 10 studies (nine population-based and one of case-controlled design) that included a definable diabetic population and assessments of cognitive function at baseline and at follow-up. These 10 studies utilised a combination of domain-specific cognitive assessments and a clinical diagnosis of dementia in the assessment of cognitive function. Diabetes was associated with either an accelerated cognitive decline or an increased incidence of dementia in eight of nine of the population-based studies. One study demonstrated a relationship between diabetes and vascular cognitive impairment, but not with other types of dementia. No association between type 2 diabetes and cognitive decline was demonstrated in the case-controlled study. These studies provide compelling evidence to support the view that people with type 2 diabetes are at increased risk of developing cognitive impairment in comparison with the general population.

Prospects of genetic research of mild cognitive impairment

Mild cognitive impairment (MCI) is a common problem in the elderly. Genetic research may yield valuable clues to improve the diagnostic and prognostic tools for MCI. As the majority of patients progress into Alzheimer's disease (AD) and other forms of dementia, the genetics of MCI cannot be separated from the genetics of AD and dementia in general. Follow-up studies of carriers of mutations underlying AD may yield valuable clues for the development of new diagnostic tools for MCI. In particular, large-scale studies of carriers of the apolipoprotein E 4 allele may still be of interest. Our knowledge of the genes involved in MCI is still very limited. In addition, we need powerful and carefully designed candidate gene studies aiming to discover new genes involved in the risk and progression of MCI. Although the genetics of MCI will be difficult to disentangle, there is ample opportunity to improve research of the genes involved.

Mild cognitive impairment: focus on diagnosis

Great interest is now devoted to elderly people with memory or other cognitive complaints who are not demented. The determination of this impairment from normality is difficult, because memory performance may decline slowly along the lifetime of the individual. On the other hand, the identification of dementia depends on the criteria used for dementia (DSM-IV or ICD-10). Furthermore, cognitive deterioration of the elderly appears to be heterogenous and may forerun not only Alzheimer's disease but also other forms of dementia. By applying a set of criteria for frontotemporal mild cognitive impairment, it was possible to identify, retrospectively, a series of patients with behavioral, affective, or speech symptoms suggestive of frontotemporal dysfunction and deficits in frontal lobe-dependent neuropsychological tests, but who have maintained activities of daily living and are not demented. These patients appear to have a high probability of progressing subsequently to dementia of the frontotemporal type. Several potential neuroprotective compounds are now being subjected to clinical trials. Should they be effective in delaying the progression to dementia, the need to detect and treat elderly people with cognitive impairment will become very important.

Combining brain imaging with microarray: isolating molecules underlying the physiologic disorders of the brain

Many diseases of the nervous system cause dysfunction by impairing neuronal physiology more than by altering brain anatomy--including age-related cognitive decline, most psychiatric disorders, and even the earliest stages of Alzheimer's disease. The absence of clear anatomical markers makes it difficult to identify targeted cells, which in turn impedes attempts to isolate the pathogenic molecules that cause physiologic disruption. Here we show how brain imaging and microarray can be used as complimentary techniques that together can characterize the cellular and molecular aspects of this class of diseases.

Imaging correlates of brain function in monkeys and rats isolates a hippocampal subregion differentially vulnerable to aging

The hippocampal formation contains a distinct population of neurons organized into separate anatomical subregions. Each hippocampal subregion expresses a unique molecular profile accounting for their differential vulnerability to mechanisms of memory dysfunction. Nevertheless, it remains unclear which hippocampal subregion is most sensitive to the effects of advancing age. Here we investigate this question by using separate imaging techniques, each assessing different correlates of neuronal function. First, we used MRI to map cerebral blood volume, an established correlate of basal metabolism, in the hippocampal subregions of young and old rhesus monkeys. Second, we used in situ hybridization to map Arc expression in the hippocampal subregions of young and old rats. Arc is an immediate early gene that is activated in a behavior-dependent manner and is correlated with spike activity. Results show that the dentate gyrus is the hippocampal subregion most sensitive to the effects of advancing age, which together with prior studies establishes a cross-species consensus. This pattern isolates the locus of age-related hippocampal dysfunction and differentiates normal aging from Alzheimer's disease.

Subjective memory complaints and objective memory impairment in the Vienna-Transdanube aging community

OBJECTIVES

To help answer the question of whether subjective memory complaints are a useful feature in classification systems addressing early stages of Alzheimer's disease.

DESIGN

A cross-sectional investigation in the context of a community-based cohort study.

SETTING

Vienna, Transdanube-a geographically defined, urban, working-class area.

PARTICIPANTS

Three hundred two nondemented 75-year-olds were examined with regard to subjective memory complaints and objective memory performance. The patients were divided into two groups with respect to subjective memory complaints and into two groups with respect to memory performance on the Fuld Object Memory Evaluation.

MEASUREMENTS

The percentage of individuals with memory complaints who also had objective memory impairment and the percentage of individuals with objective memory impairment who also complained about their memory were measured.

RESULTS

One-tenth (10.6%) (95% confidence interval (CI)=7.7-14.7) of community based sample of 75-year-old subjects complained about their memory. There was no difference between complainers and noncomplainers with regard to actual memory performance. Only 6.3% (95% CI=0.16-30.2) of memory-impaired subjects complained about their proven memory impairment.

CONCLUSION

About 94% (95% CI=69.8-99.8) of memory-impaired individuals do not complain about memory problems. Subjective memory complaints may not be a useful feature in current diagnostic criteria of mild cognitive impairment.

Use of IQ-adjusted norms to predict progressive cognitive decline in highly intelligent older individuals

Identifying high-functioning older individuals in preclinical phases of Alzheimer's disease (AD) may require more sensitive methods than the standard approach. The authors explored the utility of adjusting for premorbid intelligence to predict progressive cognitive decline or Mild Cognitive Impairment (MCI) in 42 highly intelligent older individuals. When scores were adjusted for baseline IQ, 9 participants had executive impairments, 11 had memory impairments, and 22 scored in the normal range. None were impaired according to standard age norms. Three and a half years later, 9 participants with IQ-adjusted memory impairment declined in naming, visuospatial functioning, and memory; 6 convened to MCI. Three participants with normal memory declined. Implications for using IQ-adjusted norms to predict preclinical AD are discussed.

The cognitive-enhancing properties of modafinil are limited in non-sleep-deprived middle-aged volunteers

Modafinil is a selective wakefulness-promoting agent that has been shown to enhance cognitive performance under conditions of sleep deprivation but which has equivocal effects in normal young volunteers. In a double-blind parallel group design study, 45 non-sleep-deprived middle-aged volunteers (20 men and 25 women, aged 50-67 years) were randomly allocated to receive two capsules containing placebo, 100 or 200 mg modafinil, and 3 h later they completed 100 mm visual analogue scales of mood and bodily symptoms, before and after an extensive battery of cognitive tests [pen and paper and the Cambridge Neuropsychological Test Automated Battery (CANTAB)]. There were no significant treatment-associated changes in ratings of mood or bodily symptoms and no significant effects on most of the cognitive tests used in this study. The group treated with modafinil (200 mg) was significantly faster in a simple colour naming of dots and also significantly better in a test of constructional ability (Clock Drawing Test) compared with the placebo group. However, subjects in the 200-mg group also made significantly more total errors in the Intra/Extradimensional Set Shift (ID/ED) task than both the other groups. Thus, this study found limited evidence of cognitive-enhancing properties of modafinil in healthy middle-aged volunteers.

Differential associations between entorhinal and hippocampal volumes and memory performance in older adults

Magnetic resonance imaging-derived entorhinal and hippocampal volumes were measured in 14 nondemented, community-dwelling older adults. Participants were selected so that memory scores from 2 years prior to scanning varied widely but were not deficient relative to age-appropriate norms. A median split of these memory scores defined high-memory and low-memory groups. Verbal memory scores at the time of imaging were lower, and entorhinal and hippocampal volumes were smaller, in the low-memory group than in the high-memory group. Left entorhinal cortex volume showed the strongest correlation (r= .79) with immediate recall of word lists. Left hippocampal volume showed the strongest correlation (r= .57) with delayed paragraph recall. These results suggest that entorhinal and hippocampal volumes are related to individual differences in dissociable kinds of memory performance among healthy older adults.

Later developments: molecular keys to age-related memory impairment

Age-related memory impairment, a cognitive decline not clearly related to any gross pathology, is progressive and widespread in the population, although not universal. While the mechanisms of learning and memory remain incompletely understood, the study of their molecular mechanisms is already yielding promising approaches toward therapy for such "normal" declines in the efficiency of learning. This review presents the rationale and results for two such approaches. One approach, partial inhibition of the type IV cAMP specific phosphodiesterase, appears to act indirectly. Although little evidence supports an age-related decline in this system, considerable evidence indicates that this approach can facilitate the transition from short-term to long-term memory and thus counterbalance defects in long-term memory, which may be due to other causes. A second approach, inhibition of l-type voltage gated calcium channels (LVGCCs) may be a specific corrective for a molecular pathology of aging, as substantial evidence indicates that an ongoing increase occurs throughout the lifespan in the density of these channels in hippocampal pyramidal cells, with a concomitant reduction in cellular excitability. Because LVGCCs are also crucial to extinction, a paradigm of inhibitory learning, age-related memory impairment may be an unfortunate side effect of a developmental process necessary to the maturation of the ability to suppress inappropriate behavior, an interpretation consistent with the antagonistic pleiotropy theory of aging.

Latent growth curve analyses of accelerating decline in cognitive abilities in late adulthood

Latent growth models were applied to data from the Swedish Adoption/Twin Study of Aging to discover if the rate of change in cognitive performance increased from middle age to later adulthood. The sample included 590 participants aged 44 to 88 years at first measurement. Data were gathered at 2 follow-up occasions at intervals of 3 years. Cognitive ability was assessed through 11 tests that tapped crystallized, fluid, memory, and spatial abilities and perceptual speed. Results indicated stability for measures of crystallized ability, linear age changes for many cognitive abilities, and a significant acceleration in linear decline after age 65 for measures with a large speed component. Gender differences were found only in mean level, not in rate of decline.

Silent brain infarcts and the risk of dementia and cognitive decline

BACKGROUND

Silent brain infarcts are frequently seen on magnetic resonance imaging (MRI) in healthy elderly people and may be associated with dementia and cognitive decline.

METHODS

We studied the association between silent brain infarcts and the risk of dementia and cognitive decline in 1015 participants of the prospective, population-based Rotterdam Scan Study, who were 60 to 90 years of age and free of dementia and stroke at base line. Participants underwent neuropsychological testing and cerebral MRI at base line in 1995 to 1996 and again in 1999 to 2000 and were monitored for dementia throughout the study period. We performed Cox proportional-hazards and multiple linear-regression analyses, adjusted for age, sex, and level of education and for the presence or absence of subcortical atrophy and white-matter lesions.

RESULTS

During 3697 person-years of follow-up (mean per person, 3.6 years), dementia developed in 30 of the 1015 participants. The presence of silent brain infarcts at base line more than doubled the risk of dementia (hazard ratio, 2.26; 95 percent confidence interval, 1.09 to 4.70). The presence of silent brain infarcts on the base-line MRI was associated with worse performance on neuropsychological tests and a steeper decline in global cognitive function. Silent thalamic infarcts were associated with a decline in memory performance, and nonthalamic infarcts with a decline in psychomotor speed. When participants with silent brain infarcts at base line were subdivided into those with and those without additional infarcts at follow-up, the decline in cognitive function was restricted to those with additional silent infarcts.

CONCLUSIONS

Elderly people with silent brain infarcts have an increased risk of dementia and a steeper decline in cognitive function than those without such lesions.