Memory decline in healthy older people: implications for identifying mild cognitive impairment

Neuropsychiatric symptoms and metamemory across the life span: psychometric properties of the German Multifactorial Memory Questionnaire (MMQ)

OBJECTIVE

We assessed the psychometric properties, established normative data for the German Multifactorial Memory Questionnaire (MMQ), and analyzed its association with neuropsychiatric factors across the life span to provide a validated metamemory assessment for a German-speaking population.

METHODS

The three MMQ scales (memory satisfaction, self-rated ability, and strategy application) were translated into German, considering cultural, linguistic, and conceptual aspects. To validate the MMQ and assess associations with neuropsychiatric factors, the Complainer Profile Identification, Geriatric Depression Scale, Beck Anxiety Inventory, Pittsburgh Sleep Quality Index, and Short-Form-Health Survey were applied in an online study in 336 healthy participants with follow-up after 8 months.

RESULTS

Psychometric evaluation of the German MMQ showed normal distribution of all scales and good to excellent validity, internal consistency, and retest reliability. We provide percentiles and normative data for z-score conversion. Importantly, even subclinically elevated scores in depressiveness and anxiety were associated with decreased memory satisfaction and self-rated ability. Furthermore, although the influence of age on the German MMQ scales was minimal, effects of neuropsychiatric factors such as sleep quality, anxiety, and depressiveness on MMQ Satisfaction and Ability varied across the life span.

CONCLUSIONS

Our study provides a validated German translation of the MMQ with normative data and reliability measures, including reliable change scores. We show the impact of neuropsychiatric factors on the MMQ scales across the life span and emphasize the relevance of a multifactorial approach to metamemory as a measure of individualized everyday functionality and the importance of including neuropsychiatric factors into both research and clinical assessments of metamemory.

Chanwuyi Lifestyle Medicine Program Improves Memory and Executive Functions of Older Adults With Mild Cognitive Impairment

The Chanwuyi Lifestyle Medicine Program (CLMP) was found to enhance the memory and executive functions of older adults with or without subjective memory complaints. The present study investigated whether similar beneficial effects can be extended to mild cognitive impairment (MCI). Twenty-four older adults with MCI were randomly assigned to receive the CLMP (the experimental group) or strategic memory training (SMT; the active control group) for 10 weeks. They were assessed by neuropsychological tests at baseline and post-intervention. Older adults showed similar visual and verbal memory improvements after receiving the CLMP and SMT. Yet, only those who received the CLMP showed distinct improvements in planning/organization, working memory, and attention in terms of accuracy, with greater cognitive gains associated with older age and lower levels of education and baseline cognitive functions. This study provides preliminary evidence for the effects of the CLMP on improving memory, attention, and executive functions in MCI.

An explainable machine learning based prediction model for Alzheimer's disease in China longitudinal aging study

Alzheimer's disease (AD) is the most common cause of dementia. Accurate prediction and diagnosis of AD and its prodromal stage, i.e., mild cognitive impairment (MCI), is essential for the possible delay and early treatment for the disease. In this paper, we adopt the data from the China Longitudinal Aging Study (CLAS), which was launched in 2011, and includes a joint effort of 15 institutions all over the country. Four thousand four hundred and eleven people who are at least 60 years old participated in the project, where 3,514 people completed the baseline survey. The survey collected data including demographic information, daily lifestyle, medical history, and routine physical examination. In particular, we employ ensemble learning and feature selection methods to develop an explainable prediction model for AD and MCI. Five feature selection methods and nine machine learning classifiers are applied for comparison to find the most dominant features on AD/MCI prediction. The resulting model achieves accuracy of 89.2%, sensitivity of 87.7%, and specificity of 90.7% for MCI prediction, and accuracy of 99.2%, sensitivity of 99.7%, and specificity of 98.7% for AD prediction. We further utilize the SHapley Additive exPlanations (SHAP) algorithm to visualize the specific contribution of each feature to AD/MCI prediction at both global and individual levels. Consequently, our model not only provides the prediction outcome, but also helps to understand the relationship between lifestyle/physical disease history and cognitive function, and enables clinicians to make appropriate recommendations for the elderly. Therefore, our approach provides a new perspective for the design of a computer-aided diagnosis system for AD and MCI, and has potential high clinical application value.

Fifteen Years of the Australian Imaging, Biomarkers and Lifestyle (AIBL) Study: Progress and Observations from 2,359 Older Adults Spanning the Spectrum from Cognitive Normality to Alzheimer's Disease

Background:

The Australian Imaging, Biomarkers and Lifestyle (AIBL) Study commenced in 2006 as a prospective study of 1,112 individuals (768 cognitively normal (CN), 133 with mild cognitive impairment (MCI), and 211 with Alzheimer’s disease dementia (AD)) as an ‘Inception cohort’ who underwent detailed ssessments every 18 months. Over the past decade, an additional 1247 subjects have been added as an ‘Enrichment cohort’ (as of 10 April 2019).

Objective:

Here we provide an overview of these Inception and Enrichment cohorts of more than 8,500 person-years of investigation.

Methods:

Participants underwent reassessment every 18 months including comprehensive cognitive testing, neuroimaging (magnetic resonance imaging, MRI; positron emission tomography, PET), biofluid biomarkers and lifestyle evaluations.

Results:

AIBL has made major contributions to the understanding of the natural history of AD, with cognitive and biological definitions of its three major stages: preclinical, prodromal and clinical. Early deployment of Aβ-amyloid and tau molecular PET imaging and the development of more sensitive and specific blood tests have facilitated the assessment of genetic and environmental factors which affect age at onset and rates of progression.

Conclusion:

This fifteen-year study provides a large database of highly characterized individuals with longitudinal cognitive, imaging and lifestyle data and biofluid collections, to aid in the development of interventions to delay onset, prevent or treat AD. Harmonization with similar large longitudinal cohort studies is underway to further these aims.

Technology Acceptance and Quality of Life among Older People Using a TUI Application

Good quality of life is important for healthy ageing. Studies have shown that although information and communication technology can improve older people’s quality of life, their technology acceptance level is rather low. Tangible user interfaces (TUIs) enable people to interact with the digital world through everyday physical objects, thus offering more intuitive digital environments for older people. In this study, we employ a TUI prototype to investigate the relationship between older people’s technology acceptance and quality of life, the changes in these outcome measures after using TUI, and the associations between them. The TUI prototype, Tangible Cup was used by 20 older participants over a period of three months. Data were collected using the technology acceptance model (TAM) questionnaire, the older people’s quality of life (OPQOL) questionnaire and semi-structured interviews. The results showed some positive changes in technology acceptance after the use of Tangible Cup. However, no change in the quality of life was found. While statistically significant correlations between the change in technology acceptance and the change in quality of life were observed, limitations such as small sample size and participants not accurately representing the target population should be noted. Thus, further research is needed to better understand the associations between the change in technology acceptance and the change in quality of life.

Understanding the relationship between cognition and death: a within cohort examination of cognitive measures and mortality

Despite several studies demonstrating an independent and inverse association between cognition and mortality, the nature of this association still remains unclear. To examine the association of cognition and mortality after accounting for sociodemographic, health and lifestyle factors and to explore both test and population characteristics influencing this relationship. In a population based cohort of 8585 men and women aged 48-92 years, who had cognitive assessments in 2006-2011 and were followed up till 2016 for mortality, we examined the relationship between individual cognitive tests as well as a global cognition score to compare their ability in predicting mortality and whether these differed by population characteristics. Risk of death was estimated using Cox proportional hazard regression models including sociodemographic, lifestyle and health variables, and self-reported comorbidities, as covariates in the models. Poor cognitive performance (bottom quartile of combined cognition score) was associated with higher risk of mortality, Hazard Ratio = 1.32 (95% Confidence Interval 1.09, 1.60); individual cognitive tests varied in their mortality associations and also performed differently in middle-age and older age groups. Poor cognitive performance is independently associated with higher mortality. This association is observed for global cognition and for specific cognitive abilities. Associations vary depending on the cognitive test (and domain) as well as population characteristics, namely age and education.

Relations between Concurrent Longitudinal Changes in Cognition, Depressive Symptoms, Self-Rated Health and Everyday Function in Normally Aging Octogenarians

Ability to predict and prevent incipient functional decline in older adults may help prolong independence. Cognition is related to everyday function and easily administered, sensitive cognitive tests may help identify at-risk individuals. Factors like depressive symptoms and self-rated health are also associated with functional ability and may be as important as cognition. The purpose of this study was to investigate the relationship between concurrent longitudinal changes in cognition, depression, self-rated health and everyday function in a well-defined cohort of healthy 85 year olds that were followed-up at the age of 90 in the Elderly in Linköping Screening Assessment 85 study. Regression analyses were used to determine if cognitive decline as assessed by global (the Mini-Mental State Examination) and domain specific (the Cognitive Assessment Battery, CAB) cognitive tests predicted functional decline in the context of changes in depressive symptoms and self-rated health. Results showed deterioration in most variables and as many as 83% of these community-dwelling elders experienced functional difficulties at the age of 90. Slowing-down of processing speed as assessed by the Symbol Digits Modality Test (included in the CAB) accounted for 14% of the variance in functional decline. Worsening self-rated health accounted for an additional 6%, but no other variables reached significance. These results are discussed with an eye to possible preventive interventions that may prolong independence for the steadily growing number of normally aging old-old citizens.

Variable selection in a flexible parametric mixture cure model with interval-censored data

In standard survival analysis, it is generally assumed that every individual will experience someday the event of interest. However, this is not always the case, as some individuals may not be susceptible to this event. Also, in medical studies, it is frequent that patients come to scheduled interviews and that the time to the event is only known to occur between two visits. That is, the data are interval‐censored with a cure fraction. Variable selection in such a setting is of outstanding interest. Covariates impacting the survival are not necessarily the same as those impacting the probability to experience the event. The objective of this paper is to develop a parametric but flexible statistical model to analyze data that are interval‐censored and include a fraction of cured individuals when the number of potential covariates may be large. We use the parametric mixture cure model with an accelerated failure time regression model for the survival, along with the extended generalized gamma for the error term. To overcome the issue of non‐stable and non‐continuous variable selection procedures, we extend the adaptive LASSO to our model. By means of simulation studies, we show good performance of our method and discuss the behavior of estimates with varying cure and censoring proportion. Lastly, our proposed method is illustrated with a real dataset studying the time until conversion to mild cognitive impairment, a possible precursor of Alzheimer's disease. © 2015 The Authors. Statistics in Medicine Published by John Wiley & Sons Ltd.

Blood pressure interacts with APOE ε4 to predict memory performance in a midlife sample

OBJECTIVE

Elevated blood pressure and the Apolipoprotein ε4 allele (APOE ε4) are independent risk factors for Alzheimer's disease. We sought to determine whether the combined presence of the APOE ε4 allele and elevated blood pressure is associated with lower cognitive performance in cognitively healthy middle-aged adults.

METHODS

A total of 975 participants aged 30-54 (mean age = 44.47) were genotyped for APOE. Cardiometabolic risk factors including blood pressure, lipids, and glucose were assessed and cognitive function was measured using the Trail Making Test and the Visual Reproduction and Logical Memory subtests from the Wechsler Memory Scale.

RESULTS

Multivariable regression analysis showed that the association between APOE ε4 and episodic memory performance varied as a function of systolic blood pressure (SBP), such that elevated SBP was predictive of poorer episodic memory performance only in APOE ε4 carriers (β = -.092; t = -2.614; p = .009). Notably, this association was apparent at prehypertensive levels (≥130 mmHg), even after adjusting for physical activity, depression, smoking, and other cardiometabolic risk factors.

CONCLUSIONS

The joint presence of APOE ε4 and elevated SBP, even at prehypertensive levels, is associated with lower cognitive performance in healthy, middle-aged adults. Results of this study suggest that the combination of APOE ε4 and elevated SBP may synergistically compromise memory function well before the appearance of clinically significant impairments. Interventions targeting blood pressure control in APOE ε4 carriers during midlife should be studied as a possible means to reduce the risk of cognitive decline in genetically susceptible samples.

Cognitive function in a general population of men and women: a cross sectional study in the European Investigation of Cancer-Norfolk cohort (EPIC-Norfolk)

Background

Although ageing is strongly associated with cognitive decline, a wide range of cognitive ability is observed in older populations with varying rates of change across different cognitive domains.

Methods

Cognitive function was measured as part of the third health examination of the European Prospective Investigation of Cancer in Norfolk (EPIC-Norfolk 3) between 2006 and 2011 (including measures from the pilot phase from 2004 to 2006). This was done using a battery consisting of seven previously validated cognitive function tests assessing both global function and specific domains. The battery included a shortened version of the Extended Mental State Exam (SF-EMSE); letter cancellation task; Hopkins Verbal Learning Test (HVLT); Cambridge Neuropsychological Test Automated Battery Paired Associates Learning Test (CANTAB-PAL); Visual Sensitivity Test (VST); Shortened version of the National Adult Reading Test (Short-NART) and a task to test for prospective memory. We report the distribution of cognitive function in different cognitive domains by age and sex and compare the utility of a number of assessment tests in a general population of older men and women.

Results

Cognitive test data were available for 8585 men and women taking part in EPIC-Norfolk 3. Increasing age was generally associated with declining mean cognitive function, but there was a wide range observed within each age group as well as variability across different cognitive domains. Some sex differences were also observed.

Conclusion

Descriptive data are presented for this general population sample of older men and women. There is a wide range of cognitive performance seen in this population. Though average performance declines with age, there is large individual variability across different cognitive domains. These variations may provide insights into the determinants of cognitive function in later life.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2318-14-142) contains supplementary material, which is available to authorized users.

Efficacy and safety of Ginkgo biloba extract EGb 761 in mild cognitive impairment with neuropsychiatric symptoms: a randomized, placebo-controlled, double-blind, multi-center trial

OBJECTIVE

The study was conducted to explore the effects of EGb 761 (Dr. Willmar Schwabe GmbH & Co. KG, Karlsruhe, Germany) on neuropsychiatric symptoms (NPS) and cognition in patients with mild cognitive impairment (MCI).

METHODS

One hundred and sixty patients with MCI who scored at least 6 on the 12-item Neuropsychiatric Inventory (NPI) were enrolled in this double-blind, multi-center trial and randomized to receive 240 mg EGb 761 daily or placebo for a period of 24 weeks. Effects on NPS were assessed using the NPI, the state sub-score of the State-Trait Anxiety Inventory and the Geriatric Depression Scale. Further outcome measures were the Trail-Making Test (A/B) for cognition and global ratings of change. Statistical analyses followed the intention-to-treat principle.

RESULTS

The NPI composite score decreased by 7.0 ± 4.5 (mean, standard deviation) points in the EGb 761-treated group and by 5.5 ± 5.2 in the placebo group (p = 0.001). Improvement by at least 4 points was found in 78.8% of patients treated with EGb 761 and in 55.7% of those receiving placebo (p = 0.002). Superiority of EGb 761 over placebo (p < 0.05) was also found for the State-Trait Anxiety Inventory score, the informants' global impression of change, and both Trail-Making Test scores. There were statistical trends favoring EGb 761 in the Geriatric Depression Scale and the patients' global impression of change. Adverse events (all non-serious) were reported by 37 patients taking EGb 761 and 36 patients receiving placebo.

CONCLUSIONS

EGb 761 improved NPS and cognitive performance in patients with MCI. The drug was safe and well tolerated.

Predictors of cognitive decline in 85-year-old patients without cognitive impairment at baseline: 2-year follow-up of the octabaix study

BACKGROUND/RATIONALE

To determine how many 85-year-old community-dwelling patients with good cognitive performance at baseline maintain this level at 2-year follow-up.

METHODS

We realized a longitudinal community-based study including 169 inhabitants. Patients who maintained scores >23 on the Spanish version of the Mini-Mental State Examination (MEC) were compared with the rest.

RESULTS

A total of 144 individuals (85.2%) were found maintaining a MEC score >23. Under the combined criteria 110 (65%) presented no new cognitive decline. Multiple logistic regression analysis showed that maintaining a MEC score >23 was significantly associated with having a higher MEC score at baseline (P < .001, odds ratio 1.280, 95% confidence interval 1.104-1.484).

CONCLUSION

Most oldest-old patients with good cognitive function at baseline maintain this level at 2-year follow-up.

Cognitive decline in older adults with a history of traumatic brain injury

Traumatic brain injury (TBI) is an important public health problem with potentially serious long-term neurobehavioural sequelae. There is evidence to suggest that a history of TBI can increase a person's risk of developing Alzheimer's disease. However, individuals with dementia do not usually have a history of TBI, and survivors of TBI do not invariably acquire dementia later in life. Instead, a history of traumatic brain injury, combined with brain changes associated with normal ageing, might lead to exacerbated cognitive decline in older adults. Strategies to increase or maintain cognitive reserve might help to prevent exacerbated decline after TBI. Systematic clinical assessment could help to differentiate between exacerbated cognitive decline and mild cognitive impairment, a precursor of Alzheimer's disease, with important implications for patients and their families.

Aβ amyloid, cognition, and APOE genotype in healthy older adults

BACKGROUND

Only one study has investigated the relationship between cerebral β-amyloid (Aβ), apolipoprotein E (APOE) ε4 genotype, and cognition. Although significant relationships between cerebral Aβ and cognition were observed in ε4 carriers but not noncarriers, the magnitude of this relationship was not reported. Further, when demographic variables were controlled, the influence of APOE ε4 on the relationship between cerebral Aβ and cognition dissipated.

METHODS

In 144 healthy older adults who had undergone amyloid scanning and APOE ε4 genotyping in the Australian Imaging, Biomarkers, and Lifestyle (AIBL) Flagship Study of Ageing, correlations were conducted to determine the magnitude of relationship between cerebral Aβ and cognition in ε4 carriers and noncarriers. Fisher's Z was used to compare these correlations and Cohen's q determined the magnitude of difference between correlations.

RESULTS

Cerebral Aβ was significantly associated with tasks of visual and verbal episodic memory in APOE ε4 carriers. This association was not observed in ε4 noncarriers. The relationship between cerebral Aβ and episodic memory in ε4 carriers was significantly different from that in ε4 noncarriers, and the magnitude of this difference was small to moderate.

CONCLUSIONS

In APOE ε 4 carriers, there is a moderate negative relationship between cerebral Aβ and episodic memory. This suggests that increased cerebral Aβ may signify the onset of preclinical AD, especially in healthy older adults who are genetically at risk for AD.

Intraindividual cognitive decline using a brief computerized cognitive screening test

BACKGROUND

Progressive intraindividual decline in memory and cognition is characteristic of dementia and may be useful in detecting very early Alzheimer's disease pathology.

METHODS

This study evaluated the slopes of cognitive performance over a 12-month period in 263 healthy, community-dwelling, adult volunteers aged ≥50 years. Participants completed a brief computerized battery of cognitive tests (CogState) at baseline and during 3-, 6-, 9-, and 12-month follow-up assessments. Linear mixed models were used to estimate age-adjusted mean slopes and 95% confidence intervals of change for each of the cognitive measures.

RESULTS

By defining age-adjusted mean slopes, and 95% confidence intervals for a measure of episodic memory, individuals with greater than expected decline (equal to or lower than the fifth percentile level of decline) were identified. From these, four individuals completed a full medical, neurologic, and neuropsychological evaluation, with none of them fulfilling criteria for mild cognitive impairment, but three (75%) having positive amyloid-positron emission tomographic scans.

CONCLUSIONS

Intraindividual decline in cognitive performance can be detected in otherwise healthy, community-dwelling, older persons, and this may deserve further study as a potential indicator of early Alzheimer's disease pathology.

Revised criteria for mild cognitive impairment may compromise the diagnosis of Alzheimer disease dementia

OBJECTIVE

To evaluate the potential impact of revised criteria for mild cognitive impairment (MCI), developed by a work group sponsored by the National Institute on Aging and the Alzheimer's Association, on the diagnosis of very mild and mild Alzheimer disease (AD)dementia.

DESIGN

Retrospective review of ratings of functional impairment across diagnostic categories.

SETTING

Alzheimer's Disease Centers and the National Alzheimer's Coordinating Center.

PARTICIPANTS

Individuals (N=17 535) with normal cognition,MCI, or AD dementia.

MAIN OUTCOME MEASURES

The functional ratings of individuals with normal cognition, MCI, or AD dementia who were evaluated at Alzheimer's Disease Centers and submitted to the National Alzheimer's Coordinating Center were assessed in accordance with the definition of "functional independence" allowed by the revised criteria. Pairwise demographic differences between the 3 diagnostic groups were tested using t tests for continuous variables and 2 for categorical variables.

RESULTS

Almost all (99.8%) individuals currently diagnosed with very mild AD dementia and the large majority(92.7%) of those diagnosed with mild AD dementia could be reclassified as having MCI with the revised criteria,based on their level of impairment in the Clinical Dementia Rating domains for performance of instrumental activities of daily living in the community and at home.Large percentages of these individuals with AD dementia also meet the revised "functional independence" criterion for MCI as measured by the Functional Assessment Questionnaire.

CONCLUSIONS

The categorical distinction between MCI and milder stages of AD dementia has been compromised by the revised criteria. The resulting diagnostic overlap supports the premise that "MCI due to AD" represents the earliest symptomatic stage of AD.

Learning and generalization in healthy aging: implication for frontostriatal and hippocampal function

Damage to the hippocampal and frontostriatal systems can occur across the adult life span. As these 2 systems are involved in learning processes, mild impairments of learning and generalization might be observed even in healthy aging. In this study, we examined both learning and generalization performance in 3 groups of older adults: young-older (ages 45 to 60 y), middle-older (ages 61 to 75 y), and oldest-older (ages 76 to 90 y). We used a simple computerized concurrent discrimination task in which the learning phase has shown sensitivity to frontostriatal dysfunction, and the generalization phase to hippocampal damage. We found that age significantly affected initial learning performance, but generalization was spared in all but the oldest group, with some individuals still generalizing very well. This finding suggests that (a) learning abilities are affected in healthy aging (consistent with earlier reports of frontostriatal dysfunction in healthy aging) and (b) generalization deficit does not necessarily occur in early older age. We hypothesize that generalization deficits in some in the oldest group may be related to hippocampal pathology. Our data shed light on possible neural system dysfunction in healthy aging and Alzheimer disease.

Quantitative and Qualitative Impairments in Semantic Fluency, but not Phonetic Fluency, as a Potential Risk Factor for Alzheimer's Disease

Qualitative aspects of verbal fluency may be more useful in discerning the precise cause of any quantitative deficits in phonetic or category fluency, especially in the case of mild cognitive impairment (MCI), a possible intermediate stage between normal performance and Alzheimer's disease (AD). The aim of this study was to use both quantitative and qualitative (switches and clusters) methods to compare the phonetic and category verbal fluency performance of elderly adults with no cognitive impairment (n = 51), significant memory impairment (n = 16), and AD (n = 16). As expected, the AD group displayed impairments in all quantitative and qualitative measures of the two fluency tasks relative to their age- and education-matched peers. By contrast, the amnestic MCI group produced fewer animal names on the semantic fluency task than controls and showed normal performance on the phonetic fluency task. The MCI group's inferior category fluency performance was associated with a deficit in their category-switching rate rather than word cluster size. Overall, the results indicate that a semantic measure such as category fluency when used in conjunction with a test of episodic memory may increase the sensitivity for detecting preclinical AD. Future research using external cues and other measures of set shifting capacity may assist in clarifying the origin of the amnestic MCI-specific category-switching deficiency.

Use of the CogState Brief Battery in the assessment of Alzheimer's disease related cognitive impairment in the Australian Imaging, Biomarkers and Lifestyle (AIBL) study

The aim of this study was to validate the CogState Brief Battery, which assesses psychomotor, attentional, working memory, and visual learning functions, in healthy older people and in patients with mild cognitive impairment (MCI) and Alzheimer's disease (AD), enrolled in the Australian Imaging, Biomarkers and Lifestyle (AIBL) study. In healthy older adults, weak relationships between demographic variables (e.g., education, depression) and cognitive performance were observed. In AD and MCI groups, the magnitude of impairment was greatest for tasks of working memory and memory, with a negative influence of apolipoprotein E ϵ4 status on learning but not working memory. These results suggest that the CogState Brief Battery can be used to screen for AD-related cognitive changes.

Using cognitive decline in novel trial designs for primary prevention and early disease-modifying therapy trials of Alzheimer's disease

BACKGROUND

Ideally putative disease-modifying therapies for Alzheimer's disease (AD) should be tested in patients who have minimal morbidity. Current barriers to such trials in early disease include the lack of disease-specific early biomarkers, insensitivity of quantitative cognitive outcome measures, and expensive trial designs requiring large sample sizes and long duration. This paper describes principles and progress towards a novel trial design that overcomes these problems, utilizing wide-scale cognitive performance screening to define pre-trial cognitive decline trajectories which can serve as trial outcome measures to assess AD disease-modifying efficacy.

METHODS

Theoretical principles important for the detection of intra-individual cognitive decline and a practical example are described.

RESULTS

Serial evaluations of community-based volunteers demonstrate how a screening tool method to detect subtle cognitive decline can predict in vivo amyloid pathology as a trigger for etiological evaluation. Trajectories of decline appear consistent over at least two years, suggesting they could be used as a trial inclusion criterion and ameliorable outcome measure together with other AD biomarkers. Informative trial durations could be 6-12 months, or extend to incorporate staggered random withdrawal or start designs, with as few as 20 individuals per treatment arm.

CONCLUSIONS

This trial methodology offers significant advantages over current AD trial designs, including treatment at earlier stages of disease, shorter trial duration, obviation of informed consent difficulties, smaller sample sizes, reduced cost and--given adequate screening programs--sufficient subjects for multiple simultaneous trials. Importantly, it allows the rapid evaluation of putative treatments that may only be efficacious in pre-dementia states.

Is amnestic mild cognitive impairment a useful concept?

As the world’s population continues to age, the issues of age-related memory impairment become increasingly important and relevant to individual health and quality of life, as well as an increasing public health and societal concern. The concept of mild cognitive impairment (MCI) has emerged as a response to the desire and need to identify an indolent clinical condition that would reliably predict progression to dementia, particularly Alzheimer’s disease (AD). As a result of decades of research in the field of neurodegeneration, it is becoming increasingly evident that neurodegenerative diseases begin years before the onset of clinical symptoms, and that standard clinical practice may be relatively insensitive at identifying early neurodegenerative states. The MCI concept was developed to identify the clinical parameters that define the earliest stages of the neurodegenerative process. The essence of the MCI classification is that of mild but measurable cognitive changes indicating a predisposition to progression to dementia, prior to the onset of functional decline. MCI and, more specifically, amnestic MCI were initially proposed as pathological transitional states that ultimately progress to full blown AD. However, after more than a decade of observations, it has been found that MCI subjects do not uniformly progress to dementia or AD and may revert back to normal cognitive states. While the concept of MCI may represent a valid model for characterization of the earliest stages of dementia and for delineation of risk factors, the operational definition may not adequately convey the intended concepts, and as such should be viewed with caution. Additional modifications to the concept and its operationalization are suggested in order to better identify patients with incipient AD and to guide clinical and research practices.

Contemporary review 2009: cognitive aging

This article addresses key topics in cognitive aging, intending to provide the reader with a brief overview of the current state of research in this growing, multidisciplinary field. A summary of the physiological changes in the aging brain is provided as well as a review of variables that influence cognitive abilities in older age. Normal aging differentially affects various aspects of cognition, and specific changes within various domains such as attention, executive functioning, and memory are discussed. Various theories have been proposed to account for the cognitive changes that accompany normal aging, and a brief examination of these theories is presented in the context of these domain-specific changes.

The utility of placing recollection in opposition to familiarity in early discrimination of healthy aging and very mild dementia of the Alzheimer's type

This study explored the ability to control familiarity-based information in a memory exclusion paradigm in healthy young, older adults, and early stage DAT individuals. We compared the predictive power of memory exclusion performance to standard psychometric performance in discriminating between aging and the earliest stage of DAT and between APOe4-present and APOe4-absent genotype in healthy control individuals. Participants responded "yes" to words that were previously semantically encoded, and "no" to words that were previously read aloud and to new words. The number of targets and distractors on the read "distractor" list was manipulated to investigate the degree to which aging and DAT influence the ability to recollect in the face of distractor familiarity due to repetition. Memory exclusion performance was better for healthy older adults than very mild DAT individuals and better for healthy control individuals with APOe4 allele than those without APOe4 allele even after controlling for standard psychometric performance. Discussion focuses on the importance of attentional control systems in memory retrieval and the utility of the opposition paradigm for discriminating healthy versus pathological aging.

Predicting the time of conversion to MCI in the elderly: role of verbal expression and learning

BACKGROUND

Increasing awareness that minimal or mild cognitive impairment (MCI) in the elderly may be a precursor of dementia has led to an increase in the number of people attending memory clinics. We aimed to develop a way of predicting the period of time before cognitive impairment occurs in community-dwelling elderly. The method is illustrated by the use of simple tests of different cognitive domains.

METHODS

A cohort of 241 normal elderly volunteers was followed for up to 20 years with regular assessments of cognitive abilities using the Cambridge Cognitive Examination (CAMCOG); 91 participants developed MCI. We used interval-censored survival analysis statistical methods to model which baseline cognitive tests best predicted the time to convert to MCI.

RESULTS

Out of several baseline variables, only age and CAMCOG subscores for expression and learning/memory were predictors of the time to conversion. The time to conversion was 14% shorter for each 5 years of age, 17% shorter for each point lower in the expression score, and 15% shorter for each point lower in the learning score. We present in tabular form the probability of converting to MCI over intervals between 2 and 10 years for different combinations of expression and learning scores.

CONCLUSION

In apparently normal elderly people, subtle measurable cognitive deficits that occur within the normal range on standard testing protocols reliably predict the time to clinically relevant cognitive impairment long before clinical symptoms are reported.

Apolipoprotein E-dependent accumulation of Alzheimer disease-related lesions begins in middle age

OBJECTIVE

To study the prevalence and age dependency of senile plaques (SP) and neurofibrillary tangles (NFT), the brain changes characteristic of Alzheimer disease (AD), and their association with apolipoprotein E (APOE) genotypes in a community-dwelling normal population.

METHODS

This neuropathological study used both silver staining and A beta immunohistochemistry in brain tissue microarrays, including SP coverage and NFT counts from frontal cortex and hippocampus, and APOE genotyping, and was performed on a consecutive prospective series of 603 subjects (aged between 0 and 97 years) of an unselected population living outside of institutions. Cases were subjected to autopsy following sudden or unexpected out-of-hospital death, covering 22.1% of the mortality of Tampere, Finland and its surroundings. None died of AD, although 22 (3.7%) were demented and 10 (1.7%) had memory problems.

RESULTS

Of the series, 30.8% had SP, and 42.1% had NFT; these occurred more commonly among females and showed a strong relationship with age. Both changes had already appeared at around 30 years of age, reaching an occurrence of almost 100% in the oldest. SP were more frequent in APOE epsilon 4-carriers compared with noncarriers in every age group except the oldest (>90 years). The difference was most evident during the ages 50 to 59 years, where 40.7% of epsilon 4-carriers had SP, compared with 8.2% in noncarriers (odds ratio, 8.39; 95% confidence interval, 2.55-27.62). The difference in NFT prevalence between APOE genotypes was not statistically significant in any age group.

INTERPRETATION

The brain changes associated with AD may already begin developing early in middle age, especially among APOE epsilon 4 carriers.

Detection of MCI in the clinic: evaluation of the sensitivity and specificity of a computerised test battery, the Hopkins Verbal Learning Test and the MMSE

INTRODUCTION

the sensitive detection of mild cognitive impairment (MCI) in older adults is an important problem that requires objective assessment. We evaluated whether the computerised cognitive test battery, CogState, was as sensitive to MCI as two well-validated 'paper-and-pencil' tests, the Hopkins Verbal Learning Test (HVLT) and the Mini-Mental Status Examination (MMSE).

METHODS

these tests were administered with a subjective memory questionnaire and an 'Activities of Daily Living' scale to 21 individuals with MCI and 98 cognitively healthy controls matched for sex, education and IQ levels. The sensitivity and specificity of the tests and their discrimination between groups were determined.

RESULTS

the HVLT had a maximum discrimination between controls and MCI cases of 90%, compared with 86% for CogState and 65% for the MMSE. Only CogState showed correlations with subjective memory complaints (SMC) and activities of daily living for the whole cohort when controlled for age, sex and years of education. Logistic regression analyses showed that diagnosis (control:MCI) was predicted by HVLT and a CogState ratio score. Age was a significant predictor of HVLT performance, while age and SMC predicted CogState performance. The computerised test battery was well tolerated by older adults, but presentation speed was a limiting factor for some participants.

CONCLUSIONS

overall, we conclude that the HVLT has better sensitivity for the detection of MCI in older adults than the CogState, but that CogState may enable the identification of cognitive deficits above and beyond impairments in memory.

Validity of the CogState brief battery: relationship to standardized tests and sensitivity to cognitive impairment in mild traumatic brain injury, schizophrenia, and AIDS dementia complex

This study examined the validity of the four standard psychological paradigms that have been operationally defined within the CogState brief computerized cognitive assessment battery. Construct validity was determined in a large group of healthy adults. CogState measures of processing speed, attention, working memory, and learning showed strong correlations with conventional neuropsychological measures of these same constructs (r's = .49 to .83). Criterion validity was determined by examining patterns of performance on the CogState tasks in groups of individuals with mild head injury, schizophrenia, and AIDS dementia complex. Each of these groups was impaired on the CogState performance measures (Cohen's d's = -.60 to -1.80) and the magnitude and nature of this impairment was qualitatively and quantitatively similar in each group. Taken together, the results suggest that the cognitive paradigms operationally defined in the CogState brief battery have acceptable construct and criterion validity in a neuropsychological context.

The nature of cognitive complaints in healthy older adults with and without objective memory decline

Cognitive and memory complaints were assessed in 100 healthy older adults on two occasions over 2.5 years as part of a 6-year study assessing cognition, mood, and general health factors. Diminished memory for names and actions and lapses in concentration were common complaints, regardless of the individuals' actual cognitive status. No change in cognitive complaints occurred over time, even for individuals whose memory had declined over 6 years. Cognitive complaints correlated with anxiety, depression, and general mental health but not with objectively measured memory or cognition, education or age. Complaints did not differ with gender, apolipoprotein E epsilon4 genotype, cardiovascular risk factors, or intake of sedating medications. Thus, cognitive complaints could not differentiate memory-declining older adults from cognitively normal older adults and were more closely associated with mood and general mental health than actual cognitive status, age, or potential risk factors for Alzheimer's disease. Thus, the evaluation of cognitive complaints must be broad and must consider the correspondence of complaints not only to relevant measurable cognitive abilities but also to the affect of the individual.

The ART of loss: Abeta imaging in the evaluation of Alzheimer's disease and other dementias

Molecular neuroimaging based on annihilation radiation tomographic (ART) techniques such as positron emission tomography (PET), in conjunction with related biomarkers in plasma and cerebrospinal fluid (CSF), are proving valuable in the early and differential diagnosis of Alzheimer's disease (AD). With the advent of new therapeutic strategies aimed at reducing beta-amyloid (Abeta) burden in the brain to potentially prevent or delay functional and irreversible cognitive loss, there is increased interest in developing agents that allow assessment of Abeta burden in vivo. Abeta burden as assessed by molecular imaging matches histopathological reports of Abeta plaque distribution in aging and dementia and appears more accurate than FDG for the diagnosis of AD. Abeta imaging is also a very powerful tool in the differential diagnosis of AD from fronto-temporal dementia (FTD). Although Abeta burden as assessed by PET does not correlate with measures of cognitive decline in AD, it does correlate with memory impairment and rate of memory decline in mild cognitive impairment (MCI) and healthy older subjects. Approximately 30% of asymptomatic controls present cortical (11)C-PiB retention. These observations suggest that Abeta deposition is not part of normal ageing, supporting the hypothesis that Abeta deposition occurs well before the onset of symptoms and is likely to represent preclinical AD. Further longitudinal observations are required to confirm this hypothesis and to better elucidate the role of Abeta deposition in the course of Alzheimer's disease.

Decline in verbal memory in non-demented older adults

Decline in memory function was detected in 30% of healthy community-dwelling elderly over 6 years using a task assessing delayed word list recall. Individuals with memory decline over time also demonstrated relative deficits on additional tasks of memory and learning, a task of working memory and executive function, and on a verbal (category) fluency task at their most recent assessment. These relative deficits in the performance of individuals with memory decline cannot be explained by age-related changes, education, intelligence, mood, health-related factors, or the individuals' APOE epsilon 4 status. Decline in memory performance did not result in greater complaints of cognitive difficulties when compared with normal elderly, nor did it limit overall participation in life activities. Although the significance of memory decline in the current study was not determined quantitatively, memory decline is consistent with the early deterioration characteristic of mild cognitive impairment and preclinical Alzheimer's disease and confirms the need to monitor individuals with objective memory decline, even when these individuals fall within normal limits for a given neuropsychological task.

Abeta deposits in older non-demented individuals with cognitive decline are indicative of preclinical Alzheimer's disease

Approximately 30% of healthy persons aged over 75 years show Abeta deposition at autopsy. It is postulated that this represents preclinical Alzheimer's disease (AD). We evaluated the relationship between Abeta burden as assessed by PiB PET and cognitive decline in a well-characterized, non-demented, elderly cohort. PiB PET studies and cognitive tests were performed on 34 elderly participants (age 73+/-6) from the longitudinal Melbourne Healthy Aging Study (MHAS). Subjects were classified as being cognitively 'stable' or 'declining' by an independent behavioural neurologist based on clinical assessment and serial word-list recall scores from the preceding 6-10 years. Decline was calculated from the slope of the word-list recall scores. Abeta burden was quantified using Standardized Uptake Value normalized to cerebellar cortex. Ten subjects were clinically classified as declining. At the time of the PET scans, three of the declining subjects had mild cognitive impairment, one had AD, and six were declining but remained within the normal range for age on cognitive tests. Declining subjects were much more likely to show cortical PiB binding than stable subjects (70% vs. 17%, respectively). Neocortical Abeta burden correlated with word-list recall slopes (r=-0.78) and memory function (r=-0.85) in the declining group. No correlations were observed in the stable group. Abeta burden correlated with incident memory impairment and the rate of memory decline in the non-demented ageing population. These observations suggest that neither memory decline nor Abeta deposition are part of normal ageing and likely represent preclinical AD. Further longitudinal observations are required to confirm this hypothesis.

Apolipoprotein E genotype and lifetime cognitive decline

OBJECTIVE

The relationship of apolipoprotein E (APOE) genotype to lifetime cognitive decline was examined over 22 years in a large community-based population study.

METHOD

The sample for the present study was derived from follow-up of a probability sample of the adult household residents of East Baltimore. From the Baltimore cohort of the Epidemiologic Catchment Area Study, genotype data were collected on 818 participants at the study's fourth wave between 2003 and 2004. Participants were administered the Mini-mental State Examination (MMSE) at all four study waves. Three tests of verbal learning - immediate recall, delayed recall, and word recognition - were completed at waves 3 and 4. The 659 participants for whom genetic data were available had also completed cognitive testing at all time points. Test scores and changes in these scores were examined by APOE genotype group (x/x or 4/x) in younger and older subcohorts defined by age at wave 4 (< or > or = age 65).

RESULTS

Cross-sectional wave 4 scores on all four cognitive tasks were lower in APOEepsilon4 carriers when compared to non-carriers. In longitudinal univariate models epsilon4 carriers in the younger cohort demonstrated a greater annual rate of decline on a delayed recall task and MMSE. After adjusting for covariates only the decline in the delayed recall task was significant.

CONCLUSION

We report an association between APOE genotype and decline in delayed recall and possibly MMSE over this extended time period limited to younger individuals. The lack of an association between APOE and decline in older individuals is likely to be the result of survival bias. Although a clear association exists between APOE genotype and cognitive decline or dementia in late life, these findings suggest that over the lifespan the relationship between APOE and cognitive decline is more complicated.

Lack of practice effects on neuropsychological tests as early cognitive markers of Alzheimer disease?

Reliable assessment of change from previous cognitive functioning is a prerequisite for determining the possible presence of neurodegenerative diseases such as Alzheimer's disease (AD). We investigated whether standardized change scores on the German version of the Consortium to Establish a Registry for Alzheimer's Disease-Neuropsychological Assessment Battery (CERAD-NAB) could be used for early diagnosis of AD and whether change scores on the CERAD-NAB are superior in this respect to scores recorded on 1 occasion only. Three hundred seventy-four normal control subjects were assessed twice. Data from 95 patients with mostly mild probable AD were collected at their first entry to a memory clinic and an average of 1.1 +/- 0.24 years later. It is concluded that repeated testing with the CERAD-NAB does not generally add to improved diagnostic accuracy for mild and very mild AD and cannot, therefore, be recommended as a routine clinical procedure.

Intelligence quotient-adjusted memory impairment is associated with abnormal single photon emission computed tomography perfusion

Cognitive reserve among highly intelligent older individuals makes detection of early Alzheimer's disease (AD) difficult. We tested the hypothesis that mild memory impairment determined by IQ-adjusted norms is associated with single photon emission computed tomography (SPECT) perfusion abnormality at baseline and predictive of future decline. Twenty-three subjects with a Clinical Dementia Rating (CDR) score of 0, were reclassified after scores were adjusted for IQ into two groups, 10 as having mild memory impairments for ability (IQ-MI) and 13 as memory-normal (IQ-MN). Subjects underwent cognitive and functional assessments at baseline and annual follow-up for 3 years. Perfusion SPECT was acquired at baseline. At follow-up, the IQ-MI subjects demonstrated decline in memory, visuospatial processing, and phonemic fluency, and 6 of 10 had progressed to a CDR of 0.5, while the IQ-MN subjects did not show decline. The IQ-MI group had significantly lower perfusion than the IQ-MN group in parietal/precuneus, temporal, and opercular frontal regions. In contrast, higher perfusion was observed in IQ-MI compared with IQ-MN in the left medial frontal and rostral anterior cingulate regions. IQ-adjusted memory impairment in individuals with high cognitive reserve is associated with baseline SPECT abnormality in a pattern consistent with prodromal AD and predicts subsequent cognitive and functional decline.

Cases with Mild Cognitive Impairment and Alzheimer’s Disease Fail to Benefit from Repeated Exposure to Episodic Memory Tests as Compared with Controls

Memory tests may be predictive for cognitive decline. We investigated the sensitivity and change in performance over time of the Hopkins Verbal Learning Test (HVLT) and the Mini-Mental Status Examination (MMSE) for Mild Cognitive Impairment (MCI) and Alzheimer's Disease (AD) when compared to cognitively healthy controls. Participants included elderly controls (n = 54), MCI (n = 19) and AD cases (n = 28) from OPTIMA. The MMSE and the HVLT (version 1) were administered twice to all subjects with an interval of 2-3 years.MCI and AD cases had poorer performance than controls on the HVLT and MMSE at both testing episodes (p < 0.05). The HVLT profile over time showed a learning effect in the control group (P < 0.0001), a trend to decline in the AD group (p = 0.09) and no change in the MCI group (P = 0.8). A subgroup of MCI subjects had lower HVLT scores at follow-up. The MMSE profile showed no significant change over time for all three groups (P > 0.05). The HVLT had better sensitivity and specificity compared to the MMSE for detecting MCI and AD. The HVLT is not only valuable for cross-sectional designs but has also proved to be valuable in a longitudinal design. Cognitively healthy controls showed evidence of learning strategies on the HVLT after a 2-3 year interval, with improved scores at the second testing episode. By contrast, an MCI group showed no benefits of previous exposure to this test. Lack of use of learning strategies on the HVLT may be an important marker of the likelihood of cognitive decline to MCI or dementia.

Validation Study of the Three-Objects-Three-Places Test: A Screening Test for Alzheimer's Disease

The aim of the present study was to validate a short, ecological test of episodic memory for the screening of Alzheimer's disease (AD). The validation was performed by computing intrarater reliability, homogeneity, internal coherence, convergent, discriminant and known group validities in the performance of normal subjects (N = 65), mild cognitive impairment (MCI) patients (N = 114), and AD (N = 44) and non-AD demented (N = 39) patients. Intrarater reliability was 0.88, homogeneity ranged from 0.81 to 0.97, and internal coherence was 0.87. With respect to convergent and discriminant validities, the test loaded strongly on memory factor (value = 0.64) and weakly on other nonmemory factors. The known group validity showed a specificity between 87% and 91% and a sensitivity between 92% and 100% in correctly identifying AD in age classes ranging from 50 to 65 and 66 to 80 years. The test is a valid instrument for the screening of AD.

Apolipoprotein E variants and cognition in healthy individuals: A critical opinion

The epsilon4 allele of apolipoprotein E (ApoE) is a well-established risk factor for late onset Alzheimer's disease (AD). This knowledge has generated interest in the role of ApoE variants in normal cognition. Varying degrees of cognitive dysfunction have been described in non-demented individuals with one or two epsilon4 alleles leading to suggestions that the gene plays a role in normal cognition or helps calibrate the aging process. In this paper, these hypotheses are critically evaluated. It is argued that ApoE variants play no role in cognitive development. Given the differential neurocognitive sequelae of normal aging and AD, we also suggest that accelerated aging is unlikely to account for the pattern of deficits observed in non-demented epsilon4 allele carriers. We conclude that the neuropsychological dysfunction reported in non-demented epsilon4 carriers is most likely to be the result of incipient AD.

Neuropsychological markers of progression from mild cognitive impairment to Alzheimer's disease

To find early clinical markers that may predict a likely progression to Alzheimer's disease (AD), the authors performed neuropsychological tests on 82 mild cognitive impairment (MCI) subjects. After 3 years, 38 patients developed AD while 44 retained the diagnosis of MCI. The cognitive differences between the groups were studied. Patients who developed AD showed significantly lower values than did MCI subjects in some neuropsychological scores (P = .02-.001), with sensitivities and specificities higher than 84% and 64%, respectively, for detecting early-onset AD, with a 7.9-fold increased risk of converting to AD (P < .001). Regarding the logistic regression model, the CAMCOG Memory and Perception cognitive screening items were the optimum independent tools to classify the patients who will progress to AD, showing a relative risk of progression of 10.5 (P = .002), 5.5 (P = .008), and 3.9 times (P = .05), respectively, with a sensibility of of 92.1% and a specificity 72.7%.

Apolipoprotein E epsilon4 and change in cognitive functioning in community-dwelling older adults

The relationship between apolipoprotein E (APOE) epsilon4 and change in cognition was examined in older men (n = 247; age = 75.0 +/- 3.5 years) and women (n = 79; age = 70.8 +/- 4.9 years) free of history of stroke. Participants were examined again 4.0 +/- 0.5 years later. Exclusion criteria were (1) initial scores on the Mini-Mental State Examination of 23 or less or (2) the presence of the APOE 2/4 genotype. Men with epsilon4 showed greater decline in some measures of executive function and verbal memory compared to those without epsilon4; women with epsilon4 showed greater decline in Trail Making test performance relative to women without the allele. A significant gender x APOE epsilon4 interaction was seen for change in performance on short delay cued recall. These results suggest that APOE epsilon4 is associated with cognitive decline differently in older adult men and women.

Subtle memory decline over 12 months in mild cognitive impairment

OBJECTIVE

Screening of normal older persons for progressive memory decline is a worthwhile strategy in the pursuit of the earliest possible stages of pre-clinical Alzheimer's disease (AD) or mild cognitive impairment (MCI). Reliable tests are needed to both detect MCI and measure the natural history of decline over months rather than years. We aimed to detect memory decline over 1 year in a group of older individuals with well-characterised amnestic MCI.

METHODS

The continuous learning task (CLT) from the CogState test battery was administered 8 times in 12 months to 15 individuals with MCI and 35 controls matched for age, education, IQ and gender. All subjects were recruited from an ongoing aging study. The rate of change in CLT performance over the year was compared between groups and also compared to that detected with a word list learning task and a computerised paired associate learning task.

RESULTS

At baseline, memory performance in the amnestic MCI group was significantly worse than controls on all memory tests. However, at 12 months the magnitude of the difference between the groups had increased significantly on the CLT due to decline in memory accuracy in the MCI group. No decline over 12 months was detectable on the routine memory tests.

CONCLUSIONS

Subtle memory decline is detectable in amnestic MCI using reliable and sensitive tests of memory. Such measures may assist in the early identification of AD and also in trials of putative disease-modifying therapies to be conducted over as little as 12 months.

Category fluency in mild cognitive impairment: reduced effect of practice in test-retest conditions

Verbal fluency tests are commonly used in neurocognitive and mental status examinations in patients with suspected dementia. Inflation of test scores as a result of practice effects may yield false-negative results in test-retest and multidisciplinary settings, particularly among patients with mild cognitive deficits. To address this issue, animal naming was administered twice within a 1-week period to a group of individuals referred for suspected dementia who were ultimately diagnosed with mild cognitive impairment (MCI; amnestic form), probable Alzheimer disease (AD), or no dementia. A 2 x 3 repeated-measures analysis of variance revealed a statistically significant interaction between administration time and group. Post hoc analyses indicated that nondemented controls were the only group to demonstrate a significant practice effect, producing an average of approximately three more animal names at time two. Like patients with a diagnosis of AD, subjects with amnestic MCI failed to benefit from repeated exposure to the animal naming test, and only controls showed an average improvement upon retest. This underscores the cognitive similarity between individuals diagnosed with amnestic MCI and AD and suggests that improvement upon retest may be a diagnostically useful finding.

Statistical and conceptual issues in defining post-operative cognitive dysfunction

The occurrence of post-operative cognitive dysfunction is a distressing complication following surgery. In an effort to gain a more complete understanding of patients' cognitive recovery following surgical procedures common neuropsychological assessment tools have been adopted in a repeated measures design. It is widely regarded that this represents the most comprehensive method of determining cognitive status in this population but it has resulted in a number of statistical and conceptual difficulties in attempting to infer significant change. The current paper outlines these core difficulties and provides some potential methods to overcome these.

Mild cognitive impairment as a diagnostic entity

The concept of cognitive impairment intervening between normal ageing and very early dementia has been in the literature for many years. Recently, the construct of mild cognitive impairment (MCI) has been proposed to designate an early, but abnormal, state of cognitive impairment. MCI has generated a great deal of research from both clinical and research perspectives. Numerous epidemiological studies have documented the accelerated rate of progression to dementia and Alzheimer's disease (AD) in MCI subjects and certain predictor variables appear valid. However, there has been controversy regarding the precise definition of the concept and its implementation in various clinical settings. Clinical subtypes of MCI have been proposed to broaden the concept and include prodromal forms of a variety of dementias. It is suggested that the diagnosis of MCI can be made in a fashion similar to the clinical diagnoses of dementia and AD. An algorithm is presented to assist the clinician in identifying subjects and subclassifying them into the various types of MCI. By refining the criteria for MCI, clinical trials can be designed with appropriate inclusion and exclusion restrictions to allow for the investigation of therapeutics tailored for specific targets and populations.

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.