Cognitive decline in high-functioning older adults: reserve or ascertainment bias?

Detecting cognitive decline in high-functioning older adults: The relationship between subjective cognitive concerns, frequency of high neuropsychological test scores, and the frontoparietal control network

OBJECTIVE

Neuropsychologists have difficulty detecting cognitive decline in high-functioning older adults because greater neurological change must occur before cognitive performances are low enough to indicate decline or impairment. For high-functioning older adults, early neurological changes may correspond with subjective cognitive concerns and an absence of high scores. This study compared high-functioning older adults with and without subjective cognitive concerns, hypothesizing those with cognitive concerns would have fewer high scores on neuropsychological testing and lower frontoparietal network volume, thickness, and connectivity.

METHOD

Participants had high estimated premorbid functioning (e.g., estimated intelligence ≥75th percentile or college-educated) and were divided based on subjective cognitive concerns. Participants with cognitive concerns (n = 35; 74.0 ± 9.6 years old, 62.9% female, 94.3% White) and without cognitive concerns (n = 33; 71.2 ± 7.1 years old, 75.8% female, 100% White) completed a neuropsychological battery of memory and executive function tests and underwent structural and resting-state magnetic resonance imaging, calculating frontoparietal network volume, thickness, and connectivity.

RESULTS

Participants with and without cognitive concerns had comparable numbers of low test scores (≤16th percentile), p = .103, d = .40. Participants with cognitive concerns had fewer high scores (≥75th percentile), p = .004, d = .71, and lower mean frontoparietal network volumes (left: p = .004, d = .74; right: p = .011, d = .66) and cortical thickness (left: p = .010, d = .66; right: p = .033, d = .54), but did not differ in network connectivity.

CONCLUSIONS

Among high-functioning older adults, subjective cognitive decline may correspond with an absence of high scores on neuropsychological testing and underlying changes in the frontoparietal network that would not be detected by a traditional focus on low cognitive test scores.

Eye-tracking paradigms for the assessment of mild cognitive impairment: a systematic review

Mild cognitive impairment (MCI), representing the 'transitional zone' between normal cognition and dementia, has become a novel topic in clinical research. Although early detection is crucial, it remains logistically challenging at the same time. While traditional pen-and-paper tests require in-depth training to ensure standardized administration and accurate interpretation of findings, significant technological advancements are leading to the development of procedures for the early detection of Alzheimer's disease (AD) and facilitating the diagnostic process. Some of the diagnostic protocols, however, show significant limitations that hamper their widespread adoption. Concerns about the social and economic implications of the increasing incidence of AD underline the need for reliable, non-invasive, cost-effective, and timely cognitive scoring methodologies. For instance, modern clinical studies report significant oculomotor impairments among patients with MCI, who perform poorly in visual paired-comparison tasks by ascribing less attentional resources to novel stimuli. To accelerate the Global Action Plan on the Public Health Response to Dementia 2017-2025, this work provides an overview of research on saccadic and exploratory eye-movement deficits among older adults with MCI. The review protocol was drafted based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Electronic databases were systematically searched to identify peer-reviewed articles published between 2017 and 2022 that examined visual processing in older adults with MCI and reported gaze parameters as potential biomarkers. Moreover, following the contemporary trend for remote healthcare technologies, we reviewed studies that implemented non-commercial eye-tracking instrumentation in order to detect information processing impairments among the MCI population. Based on the gathered literature, eye-tracking-based paradigms may ameliorate the screening limitations of traditional cognitive assessments and contribute to early AD detection. However, in order to translate the findings pertaining to abnormal gaze behavior into clinical applications, it is imperative to conduct longitudinal investigations in both laboratory-based and ecologically valid settings.

Gait Analysis under Spatial Navigation Task in Elderly People-A Pilot Study

A decline in the Spatial Navigation (SN) abilities has been observed in the course of healthy aging. Walking is an inseparable part of the navigation process; however, research tasks overlook this aspect in studies involving seniors. The present study was designed to overcome this limitation by recording gait parameters during natural environment navigation and to determine gait indicators that most accurately assign the participants to the proper age category. Thirteen elderly (mean age = 69.1 ± 5.4 year) and sixteen young women (mean age = 21.5 ± 2.2 year) equipped with gait sensors were asked to learn a path while walking in a real building (Learning Phase), reproduce the path (Memory Phase) and reach targets after a 30 min delay (Delayed Phase). The Receiver Operating Characteristics (ROC) analysis showed that our self-developed Gait Style Change indicator, that is, the difference in the probability of feet landing between particular SN task phases, classified the participants into either the elderly or the young group with the highest accuracy (0.91). The second most important indicator, the Task-Related (step counts in each SN task phase), achieved the accuracy discrimination of 0.83. The gait indicators, comprising single gait parameters measured while navigating, might be considered as accurately differentiating older from younger people.

Contributions of Modifiable Risk Factors to Dementia Incidence: A Bayesian Network Analysis

OBJECTIVE

To determine and compare the contributions of modifiable risk factors (RFs) with the prevention of dementia in older adults.

DESIGN

A systematic review and Bayesian network meta-analysis (NMA). The observational group was set as a reference to collect all existing RFs and compare them with each other.

SETTING AND PARTICIPANTS

An exhaustive and comprehensive literature search strategy was used to identify relevant prospective cohort studies from several online databases from their inception to May 1, 2019. Participants without dementia were adults aged greater than 50 years.

MEASURES

The required data were extracted from the eligible studies to facilitate the Bayesian NMA.

RESULTS

Forty-three cohort studies with 277,294 participants were included in this NMA. Using the observation group as the reference, all defined RFs, except for antioxidants, were associated with lower risks of all-cause dementia [no sleep disturbances (odds ratio, OR 0.43, 95% credible interval, CrI 0.24-0.62), a high level of education (OR 0.50, 95% CrI 0.34-0.66), no history of diabetes (OR 0.57, 95% CrI 0.36-0.78), nonobese patients (OR 0.61, 95% CrI 0.39-0.83), no smoking history (OR 0.62, 95% CrI 0.45-0.79), living with family members (OR 0.67, 95% CrI 0.45-0.89), participation in physical exercise (OR 0.73, 95% CrI 0.46-0.94), abstinence from drinking (OR 0.78, 95% CrI 0.56-0.99), and no history of hypertension (OR 0.80, 95% CrI 0.65-0.96)].

CONCLUSIONS/RELEVANCE

The findings provide reliable support for the hypothesis that modifiable somatic and lifestyle factors are strong predictors of all-cause dementia.

Differential Associations Between Volumes of Atrophic Cortical Brain Regions and Memory Performances in Early and Late Mild Cognitive Impairment

Background

Early and late mild cognitive impairment (MCI) patients have been reported to have a distinctive prognosis of converting to Alzheimer’s disease.

Objective

To evaluate the difference in gray matter volume and assess the association between cognitive function evaluated by comprehensive cognitive function test, and cortical thickness across healthy controls (HCs) (n = 37), early (n = 30), and late MCI patients (n = 35).

Methods

Differences in gray matter volume were evaluated by whole brain voxel-based morphometry across the groups. Multiple regression analysis was used to analyze group by memory performance interactions for the normalized gray matter volume.

Results

The early MCI group showed reduced gray matter volume in the right middle temporal gyrus in comparison to the HC group. The late MCI group displayed atrophy in the left parahippocampal gyrus in comparison to the HC group. Late MCI patients exhibited a decreased gray matter volume in the left fusiform gyrus in comparison to patients in the early MCI group (Monte Carlo simulation corrected p < 0.01, Tukey post hoc tests). Furthermore, there was a significant group (HC vs. early MCI) by memory performance interaction for the normalized cortical volume of the right middle temporal gyrus. Additionally, a significant group (early MCI vs. late MCI) by memory performance interaction was found for the normalized gray matter volume of the left fusiform gyrus (p < 0.001).

Conclusion

Early and late MCI patients showed distinctive associations of gray matter volumes in compensatory brain regions with memory performances. The findings can contribute to a better understanding of the structural changes in compensatory brain regions to elucidate memory decline in the trajectory of the subdivided prodromal stages of the Alzheimer’s disease (AD).

Operationalized definition of older adults with high cognitive performance

Recently, there has been an increasing number of studies on exceptional cognitive aging. Herein, we aim to objectively provide the operationalized characterization of older adults with unusually high memory ability. Some authors have defined them as "SuperAgers", individuals aged 80 years or older with memory ability similar or superior to middle-aged subjects. On the other hand, the terminology "high-performing older adults" (HPOA) seems to appropriately conceptualize these individuals without exaggeration. A threshold for age is not a reliable criterion, but may be defined as 75 and 80 years of age for developing and developed countries, respectively. We propose that HPOA may exhibit episodic memory test scores equal to or greater than those of individuals aged 50-60 years, according to the validated tables for the respective country. This group must also have global cognition scores within expected average values for age and education. Executive functioning may play a central role in the exceptional memory performance of this group. Further studies are essential to confirm existing findings and may provide important evidence for cognitive aging theory and the neurobiology of dementia.

Reliable change and minimum clinically important difference (MCID) of the Repeatable Battery for the Assessment of Neuropsychology Status (RBANS) in a heterogeneous dementia sample: Support for reliable change methods but not the MCID

We compare reliable change scores and recently published anchor-based cutoffs for minimum clinically important difference (MCID) for the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) in a sample of patients diagnosed with various forms of dementia. For memory clinic patients with dementia evaluated twice over a one-year interval (N = 53), observed retest RBANS index scores were compared with predicted retest index scores based on regression formulae developed from cognitively healthy older adults. Patient RBANS change scores were also compared to suggested MCID anchors. Patients with dementia demonstrated a reliable decline on most RBANS indices, with evidence that the Visuospatial/Constructional and Language Indices might be less sensitive to decline over time. Although there was consistency between MCID and reliable changes in this sample, there was a substantial proportion where the MCID was exceeded, with no reliable change. We attempted to create MCIDs from the Clinical Dementia Rating Sum of Box scores for RBANS reliable change scores, but failed to find significant associations. Overall, the findings support use of the regression based reliable change approach, but we caution use of the MCID approach for the RBANS.

Consensus Approaches to Identify Incident Dementia in Cohort Studies: Systematic Review and Approach in the Successful Aging after Elective Surgery Study

OBJECTIVES

To survey the current methods used to ascertain dementia and mild cognitive impairment (MCI) in longitudinal cohort studies, to categorize differences in approaches and to identify key components of expert panel methodology in current use.

METHODS

We searched PubMed for the past 10 years, from March 6, 2007 to March 6, 2017 using a combination of controlled vocabulary and keyword terms to identify expert panel consensus methods used to diagnose MCI or dementia in large cohort studies written in English. From these results, we identified a framework for reporting standards and describe as an exemplar the clinical consensus procedure used in an ongoing study of elective surgery patients (the Successful Aging after Elective Surgery study).

RESULTS

Thirty-one articles representing unique cohorts were included. Among published methods, membership of experts panel varied significantly. There was more similarity in what types of information was use to ascertain disease status. However, information describing the diagnostic decision process and resolution of disagreements was often lacking.

CONCLUSIONS

Methods used for expert panel diagnosis of MCI and dementia in large cohort studies are widely variable, and there is a need for more standardized reporting of these approaches. By describing the procedure in which our expert panel achieved consensus diagnoses, we hope to encourage the development and publication of well-founded and reproducible methods for diagnosis of MCI and dementia in longitudinal studies.

The conceptualization and measurement of cognitive reserve using common proxy indicators: Testing some tenable reflective and formative models

INTRODUCTION

The examination of cognitive reserve (CR) literature reveals a lack of consensus regarding conceptualization and pervasive problems with its measurement. This study aimed at examining the conceptual nature of CR through the analysis of reflective and formative models using eight proxies commonly employed in the CR literature. We hypothesized that all CR proxies would significantly contribute to a one-factor reflective model and that educational and occupational attainment would produce the strongest loadings on a single CR factor.

METHOD

The sample consisted of 149 participants (82 male/67 female), with 18.1 average years of education and ages of 45-99 years. Participants were assessed for eight proxies of CR (parent socioeconomic status, intellectual functioning, level of education, health literacy, occupational prestige, life leisure activities, physical activities, and spiritual and religious activities). Primary statistical analyses consisted of confirmatory factor analysis (CFA) to test reflective models and structural equation modeling (SEM) to evaluate multiple indicators multiple causes (MIMIC) models.

RESULTS

CFA did not produce compelling support for a unitary CR construct when using all eight of our CR proxy variables in a reflective model but fairly cogent evidence for a one-factor model with four variable proxies. A second three-factor reflective model based upon an exploratory principal components analysis of the eight proxies was tested using CFA. Though all eight indicators significantly loaded on their assigned factors, evidence in support of overall model fit was mixed. Based upon the results involving the three-factor reflective model, two alternative formative models were developed and evaluated. While some support was obtained for both, the model in which the formative influences were specified as latent variables appeared to best account for the contributions of all eight proxies to the CR construct.

CONCLUSION

While the findings provide partial support for our hypothesis regarding CR as a one-dimensional reflective construct, the results strongly suggest that the construct is more complex than what can be captured in a reflective model alone. There is a need for theory to better identify and differentiate formative from reflective indicators and to articulate the mechanisms by which CR develops and operates.

Regional brain shrinkage and change in cognitive performance over two years: The bidirectional influences of the brain and cognitive reserve factors

We examined relationships between regional brain shrinkage and changes in cognitive performance, while taking into account the influence of chronological age, vascular risk, Apolipoprotein E variant and socioeconomic status. Regional brain volumes and cognitive performance were assessed in 167 healthy adults (age 19-79 at baseline), 90 of whom returned for the follow-up after two years. Brain volumes were measured in six regions of interest (ROIs): lateral prefrontal cortex (LPFC), prefrontal white matter (PFw), hippocampus (Hc), parahippocampal gyrus (PhG), cerebellar hemispheres (CbH), and primary visual cortex (VC), and cognitive performance was evaluated in three domains: episodic memory (EM), fluid intelligence (Gf), and vocabulary (V). Average volume loss was observed in Hc, PhG and CbH, but reliable individual differences were noted in all examined ROIs. Average positive change was observed in EM and V performance but not in Gf scores, yet only the last evidenced individual differences in change. We observed reciprocal influences among neuroanatomical and cognitive variables. Larger brain volumes at baseline predicted greater individual gains in Gf, but differences in LPFC volume change were in part explained by baseline level of cognitive performance. In one region (PFw), individual change in volume was coupled with change in Gf. Larger initial brain volumes did not predict slower shrinkage. The results underscore the complex role of brain maintenance and cognitive reserve in adult development.

Emergence of mild cognitive impairment in late middle-aged adults in the wisconsin registry for Alzheimer's prevention

AIM

It is difficult to reliably detect the earliest signs of Alzheimer's disease (AD)-associated cognitive impairment. Our aim was to compare 3 psychometric methods of identifying amnestic mild cognitive impairment (aMCI) in a middle-aged longitudinal cohort enriched for AD risk.

METHODS

Wisconsin Registry for Alzheimer's Prevention (WRAP) participants with 3 waves of cognitive assessment over approximately 6 years were coded as meeting each of 3 psychometric aMCI definitions: (a) 'aMCI standard-baseline' used published norms to establish cutoffs for baseline performance; (b) 'aMCI robust-baseline' applied WRAP-specific robust norms to baseline, and (c) 'aMCI robust-multiwave' applied these robust norms across 3 waves of assessment. Each group was compared to a cognitively healthy subset.

RESULTS

Half the aMCI standard-baseline and one third of the aMCI robust-baseline group reverted to normal ranges at follow-up. Only the aMCI robust-multiwave method had an aMCI × age interaction showing significantly worse age-related memory declines in the aMCI group compared to the cognitively healthy group over 6 years of follow-up.

CONCLUSION

Both cross-sectional methods showed instability over time, with many reverting to normal performance after baseline. The multiwave approach identified a group who showed progressive memory declines over 3 visits. Being able to detect progressive decline in late middle age is a critical step in improving prevention efforts.

Ascertainment bias in dementias: a secondary to tertiary centre analysis in Central Italy and conceptual review

BACKGROUND AND AIMS

Ascertainment bias (AB) indicates a bias of an evaluation centre in estimating the prevalence/incidence of a disease due to the specific expertise of the centre. The aim of our study was to evaluate classification of different types of dementia in new cases appearing in secondary and tertiary centres, in order to evidence possible occurrence of AB in the various (secondary to tertiary) dementia centres.

METHODS

To assess the mechanism of AB, the rates of new cases of the different forms of dementia reported by different centres were compared. The centres involved in the study were 11 hospital-based centres including a tertiary centre, located in the University Department of Clinical Neurology. The tertiary centre is endowed with state-of-the-art diagnostic facilities and its scientific production is prominently focused on dementia with Lewy bodies (DLB) thus suggesting the possible occurrence of a bias. Four main categories of dementia were identified: Alzheimer's disease (AD), DLB, fronto-temporal dementia (FTD), vascular dementia (VaD), with other forms in a category apart. The classification rate of new cases of dementia in the tertiary centre was compared with rates reported by secondary centres and rates of recoding were calculated during a follow-up of 2 years.

RESULTS

The study classified 2,042 newly diagnosed cases of dementia in a population of 1,370,000 inhabitants of which 315,000 were older than 65. AD was categorized in 48-52 % of cases, DLB in 25-28 %, FTD in 2-4 % and VaD in 17-28 %. During the 2-year follow-up the diagnosis was re-classified in 40 patients (3 %). The rate of recoding was 5 % in the tertiary centre, 2-8 % in referrals from secondary to tertiary centre, 2-10 % in recodings performed in secondary centres and addressed to tertiary centre. Recoding or percentages of new cases of AD or DLB were not different in the comparison between secondary or between secondary and tertiary centres. FTD and VaD were instead significantly recoded.

CONCLUSION

The results of the study suggest that in a homogeneous area, AB is not interfering with diagnosis of AD or DLB.

Relationship between education and dementia: an updated systematic review

OBJECTIVE

The purpose of this study was to review the relationship between education and dementia.

METHODS

A systematic literature review was conducted of all published studies examining the relationship between education and dementia listed in the PubMed and PsycINFO databases from January 1985 to July 2010. The inclusion criteria were a measure of education and a dementia diagnosis by a standardized diagnostic procedure. Alzheimer disease and Total Dementia were the outcomes.

RESULTS

A total of 88 study populations from 71 studies met inclusion criteria. Overall, 51 studies (58%) reported significant effects of lower education on risk for dementia, whereas 37 studies (42%) reported no significant relationship. A relationship between education and risk for dementia was more consistent in developed regions compared with developing regions. Age, sex, race/ethnicity, and geographical region moderated the relationship.

CONCLUSIONS

Lower education was associated with a greater risk for dementia in many but not all studies. The level of education associated with risk for dementia varied by study population and more years of education did not uniformly attenuate the risk for dementia. It seemed that a more consistent relationship with dementia occurred when years of education reflected cognitive capacity, suggesting that the effect of education on risk for dementia may be best evaluated within the context of a lifespan developmental model.

[Does intellectual activity prevent cognitive impairment? Relationships between cognitive reserve and mild cognitive impairment]

An in-depth review is presented of the role that cognitive reserve plays in the emergence of (mild cognitive impairment (MCI), and its progression to dementia by using different indicators. The studies reviewed provide support to the hypothesis that the reserve influences the manifestation of symptoms of cognitive impairment and at least partially, in its progression to dementia. The role of indicators of reserve are discussed, such as educational level, work complexity and cognitive activity in these processes. A model is also presented that argues that people with MCI and low reserves show a steeper decline early in the process of deterioration, compared to the high level of reserve this marked deterioration would have at the end of the process, due to the protective role of this reserve. This raises the need for more empirical research to help consolidate this theoretical model.

Operationalizing diagnostic criteria for Alzheimer's disease and other age-related cognitive impairment-Part 1

In this article, the challenges faced by several noted population studies for Alzheimer dementia in operationalizing current clinical diagnostic criteria for Alzheimer's disease (AD) have been reviewed. Differences in case ascertainment, methodological biases, cultural and educational influences on test performance, inclusion of special populations such as underrepresented minorities and the oldest old, and detection of the earliest symptomatic stages of underlying AD have been considered. Classification of Alzheimer dementia may be improved by the incorporation of biomarkers for AD if the sensitivity, specificity, and predictive value of the biomarkers are established and if they are appropriate for epidemiological studies, as may occur should a plasma biomarker be developed. Biomarkers for AD could also facilitate studies of the interactions of various forms of neurodegenerative disorders with cerebrovascular disease, resulting in "mixed dementia".

Ascertainment bias in the clinical diagnosis of Alzheimer disease

BACKGROUND

The clinical diagnosis of Alzheimer disease (AD) is often based, at least in part, on poor cognitive test performance compared with normative values.

OBJECTIVE

To examine the presence and extent of an ascertainment bias (omission of affected individuals) produced by such criteria when applied as early as possible in the course of the disease.

DESIGN

Longitudinal study (1979-2008).

SETTING

Washington University Alzheimer Disease Research Center, St Louis, Missouri.

PARTICIPANTS

Of 78 individuals aged 65 to 101 years enrolled as healthy controls, 55 later developed autopsy-confirmed AD; 23 remained cognitively healthy and did not have neuropathologic AD.

MAIN OUTCOME MEASURES

Criteria for the diagnosis of AD based on various cutoff points (1.5, 1.0, and 0.5 SDs below the mean for robust test norms) for 2 standard psychometric measures from each of 3 cognitive domains (episodic memory, visuospatial ability, and working memory) were applied to data from the first assessment associated with an independent clinical diagnosis of cognitive impairment for those who developed symptomatic AD and from the last assessment for those who did not.

RESULTS

Areas under the curve from receiver operating characteristic analyses ranged from 0.71 to 0.49; sensitivities and specificities were unsatisfactory even after adjusting for age and education, using combinations of tests, or examining longitudinal decline before clinical diagnosis.

CONCLUSION

Reliance on divergence from group normative values to determine initial cognitive decline caused by AD results in failure to include people in the initial symptomatic stage of the illness.

Education, the brain and dementia: neuroprotection or compensation?

The potential protective role of education for dementia is an area of major interest. Almost all older people have some pathology in their brain at death but have not necessarily died with dementia. We have explored these two observations in large population-based cohort studies (Epidemiological Clinicopathological Studies in Europe; EClipSE) in an investigation of the relationships of brain pathology at death, clinical dementia and time in education, testing the hypothesis that greater exposure to education reduces the risk of dementia. EClipSE has harmonized longitudinal clinical data and neuropathology from three longstanding population-based studies that included post-mortem brain donation. These three studies started between 1985 and 1991. Number of years of education during earlier life was recorded at baseline. Incident dementia was detected through follow-up interviews, complemented by retrospective informant interviews, death certificate data and linked health/social records (dependent on study) after death. Dementia-related neuropathologies were assessed in each study in a comparable manner based on the Consortium to Establish a Registry for Alzheimer's Disease protocol. Eight hundred and seventy-two brain donors were included, of whom 56% were demented at death. Longer years in education were associated with decreased dementia risk and greater brain weight but had no relationship to neurodegenerative or vascular pathologies. The associations between neuropathological variables and clinical dementia differed according to the 'dose' of education such that more education reduced dementia risk largely independently of severity of pathology. More education did not protect individuals from developing neurodegenerative and vascular neuropathology by the time they died but it did appear to mitigate the impact of pathology on the clinical expression of dementia before death. The findings suggest that an understanding of the mechanisms leading to functional protection in the presence of pathology may be of considerable value to society.

Age corrections and dementia classification accuracy

In contrast to expectations, demographic corrections to reduce biases against those of advanced age or few years of education does not universally improve diagnostic classification accuracy. Age corrections may be particularly problematic because age is also a risk factor for a dementia diagnosis. We found that simulating increased risk for dementia based on demographic variables, such as age, reduced the overall classification accuracy for demographically corrected simulated scores relative to the raw, uncorrected test scores. In clinical data with a small magnitude of association between age and dementia diagnosis, we found equivalent overall classification accuracy for demographically corrected and raw test scores. Regardless of the overall classification accuracy results, cutoff comparisons (16th and 9th percentiles) in clinical and simulated data demonstrated that for the most part, the sensitivity of raw scores was higher than the sensitivity of demographically corrected scores, but the specificity of scores corrected with normative data was superior.

Memory score discrepancies by healthy middle-aged and older individuals: the contributions of age and education

The aim of this study was to examine discrepancies between immediate/delayed recall and recall/working memory in middle-aged and older persons by age and education. Participants were 322 healthy individuals from the community who were stratified into three age and three education groups. Immediate and delayed recall distributions of WMS-III Logical Memory (LM) scores approximated normal curves, and LM savings scores showed a significant, but small, effect of age. LM (immediate, delayed) and Letter-Number Sequencing (LNS) discrepancies varied as a function of age and education. The difference between LM and LNS was not significant in the younger and less educated participants, but increased with age in the most educated group, and in the oldest group LNS exceeded LM (immediate and delayed). The results indicate deterioration in encoding and retrieval, rather than storage, with age, and show a differential, but small, effect of age and education on the memory measures. Working memory was resistant to age-related decline relative to immediate and delayed recall in the oldest, most educated group. Delayed recall-working memory discrepancy is relatively stable with age and education and may be a useful index of the onset of memory pathology across different ages and levels of education.

Who does well after a stroke? The Sydney stroke study

Research addressing positive outcomes one year after stroke has been limited. The sample comprised 125 participants with complete Activities of Daily Living (ADL), Instrumental Activities of Daily Living (IADL) and Mini-Mental State Examination (MMSE) scale scores at baseline ( approximately 4 months after ischaemic stroke) and at follow-up (1 year later), 31 persons were defined as having a favourable outcome (an MMSE score of >or=28/30 and combined ADL/IADL score equal to 14/14 at follow-up) and 94 as having a poorer outcome. Predictors of a favourable outcome following stroke included being younger, having higher premorbid IQ, no atrial fibrillation, no dementia, less apathy and fewer intercurrent cerebrovascular events. We conclude that people can have good outcomes in the year after stroke except if they experience further cerebrovascular events and/or have risk factors for cerebrovascular disease. Brain reserve appears to be protective.

The emergence of cognitive discrepancies in preclinical Alzheimer's disease: a six-year case study

We present neuropsychological data from an 81-year-old individual who was followed over a six-year period, initially as a healthy control participant. She performed above age-adjusted cutoff scores for impairment on most neuropsychological tests, including learning and memory measures, until the final assessment when she received a diagnosis of probable Alzheimer's disease (AD). Despite generally normal scores on individual cognitive tests, her cognitive profile revealed increasingly large cognitive discrepancies when contrasting verbal versus visuospatial tasks, and complex versus basic-level tasks. The present case provides intriguing evidence that cognitive-discrepancy measures could improve our ability to detect subtle changes in cognition at the earliest, preclinical stages of AD.

Impairment versus deficiency in neuropsychological assessment: Implications for ecological validity

Neuropsychological test interpretation has relied on pre- and postmorbid comparisons, as exemplified by the use of demographically adjusted normative data. We argue that, when the assessment goal is to predict real-world functioning, this interpretive method should be supplemented by "absolute" scores. Such scores are derived from comparisons with the general healthy adult population (i.e., demographically unadjusted normative data) and reflect examinees' current ability, that is, the interaction between premorbid and injury/disease-related factors. In support of this view, we found that substantial discrepancies between demographically adjusted and absolute scores were common in a traumatic brain injury sample, especially in participants with certain demographic profiles. Absolute scores predicted selected measures of functional outcome better than demographically adjusted scores and also classified participants' functional status more accurately, to the extent that these scores diverged. In conclusion, the ecological validity of neuropsychological tests may be improved by the consideration of absolute scores. (JINS, 2009, 15, 94-102.).

Brain reserve and the prevention of dementia

PURPOSE OF REVIEW

To evaluate and synthesize recent evidence linking mental activity and dementia risk, which commonly invokes 'brain reserve' as the mediating construct.

RECENT FINDINGS

Brain reserve has acquired several interpretations; however, the most reliable and practical definition focuses at the behavioural level by assessing frequency and range of participation in complex mental activities. Epidemiological research suggests a clear and consistent link of high brain reserve with reduced dementia risk. Furthermore, emerging clinical trials of cognitive exercise suggest that it may be effective for the prevention of longitudinal cognitive and functional decline. Recent animal studies implicate several mechanisms, including disease-dependent and disease-independent compensatory pathways.

SUMMARY

Given the precipitous forecasts for dementia over the coming decades, effective preventive strategies are of utmost importance. Findings from brain reserve studies now meet many of the formal criteria for causal agency between complex mental activity and reduced dementia risk. Key clinical trials are therefore under way to test these claims and results are keenly awaited.

The effects of HIV on P300 are moderated by familial risk for substance dependence: implications for a theory of brain reserve

BACKGROUND

The goal of the study was to test the validity of additive versus synergistic versus underadditive versions of brain reserve theory within the context of HIV/AIDS. In addition, it tested the convergent validity of 2 operational definitions of premorbid reserve: verbal IQ (VIQ) and a family history (FH) of substance abuse or dependence.

METHODS

Seventy HIV-1 seronegative and 115 HIV-1 seropositive male and female volunteers were assigned to 4 subgroups defined by the crossing of a VIQ score < versus > or = 90 with the presence versus absence of a paternal history of alcohol, cocaine, or opiate abuse or dependence. The principal dependent measure was the P300 event related brain potential elicited during the Stroop color-word interference task.

RESULTS

The principal finding was an underadditive effect of FH plus HIV/AIDS on P300 area over the frontal region: FH reduced frontal scalp P300 to such a degree that the additional effects of HIV/AIDS were blunted. The alternate operational definition of brain reserve, VIQ, had no effect on P300 and did not alter the effects of HIV/AIDS.

CONCLUSIONS

Familial risk for substance dependence and low VIQ compromise different aspects of brain structure and/or function and therefore differ in their relationship to HIV/AIDS and P300. Genetic differences associated with familial risk may reduce brain reserve to such a degree that the neurophysiological effects of HIV/AIDS can no longer be measured.

Pattern and progression of cognitive decline in Alzheimer's disease: role of premorbid intelligence and ApoE genotype

BACKGROUND/AIMS

Because of controversial results across studies, we evaluated the predictive value of premorbid intelligence and the apolipoprotein E (ApoE) genotype on baseline and progression of cognitive performance in Alzheimer's disease (AD).

METHODS

Eighty-five mild AD cases, ApoE genotyped and included in a longitudinal cliniconeuropsychological-genetic study, underwent a premorbid intelligence test and up to 11 (average 5) neuropsychological assessments. We applied linear- and logistic-regression models for cross-sectional data and mixed models for longitudinal ones.

RESULTS

Higher premorbid intelligence was associated with higher global, executive and memory performance, while the ApoE epsilon 4 allele was specifically related to poorer memory performance. The premorbid intelligence-ApoE epsilon 4/epsilon 4 interaction was significant, with higher premorbid intelligence scores reducing the detrimental effect of ApoE epsilon 4 homozygosity on memory performance. Higher premorbid intelligence, but not the ApoE epsilon 4 allele, was related to faster memory deficit progression.

CONCLUSION

The association of higher premorbid intelligence with better baseline cognitive performance and faster memory decline, as well as its interaction with the ApoE genotype, strengthens the role of cognitive reserve in shaping the disease's clinical expression. Our findings confirm that the epsilon 4 allele affects memory deficit at baseline but does not exert any influence on the rate of cognitive decline.

Cognitive decline and survival in Alzheimer's disease according to education level

OBJECTIVE

We tested the hypothesis that a higher education level is associated with faster cognitive decline and lower survival in a cohort of 670 Alzheimer's disease patients, followed for 3.5 years at the Lille-Bailleul memory centre.

METHODS

The patients were categorized in 3 groups according to educational levels: low (<or=8 years), intermediate (9-12 years) and high (>12 years). Cognitive function was measured with the Mini Mental State Examination (MMSE) and the Mattis Dementia Rating Scale (DRS). Survival was analyzed with a Cox model. Analyses were adjusted for age, sex, cholinesterase inhibitor treatment, diabetes, hypertension, visible vascular lesions on MRI, baseline DRS and MMSE.

RESULTS

The adjusted mixed random model showed that MMSE declined faster for patients with high and intermediate educational levels compared with those with a low educational level (p < 0.0001). The mean annually adjusted DRS decline was highest for the groups with the most education (p = 0.05). The mortality risk was not higher in the better-educated groups (high vs. low: RR = 0.84; 95% CI = 0.35-1.99, intermediate vs. low: RR = 0.82; 95% CI = 0.41-1.63).

CONCLUSION

In our cohort, highly educated patients had a faster cognitive decline than less educated patients but similar mortality rates. Our findings support the cognitive reserve hypothesis.

IQ-based norms for highly intelligent adults

This study presents normative data of commonly used neuropsychological tests administered to 75 individuals with high levels of intelligence (estimated IQ > or = 120). Participants were living independently in the community with ages ranging from 44 to 86. To avoid including individuals with an incipient dementia, we selected subjects who scored within the normal range on all cognitive tests for at least a two-year period. The norms are presented in table format to help clinicians easily identify a typical cognitive performance in highly intelligent individuals and to provide a useful guide for detecting abnormal cognitive decline in individuals at risk for progressive dementia.

Education and dementia: a meta-analytic study

Considerable controversy exists about the role of education in the risk of dementia. Individual studies have not been conclusive so far. To examine the hypothesis that lower education is associated with a higher risk of dementia, we carried out a meta-analysis. Observational studies published as of October 2005 that examined the association between education and risk of dementia were systematically reviewed. Relative risks (RRs) and odds ratios were extracted from cohort and case-control studies. We first compared the risk of dementia in subjects with high level of education with the risk of dementia in those with low educational level. In a subsequent analysis, we compared the risk of persons with high education with the risk of subjects with education level other than high (medium, low). We weighted log RRs for cohort studies or odds ratios by the inverse of their variances. Nineteen studies were included in our meta-analysis (13 cohort and 6 case-control studies). RRs for low versus high education level were: Alzheimer's disease (AD) 1.80 (95% CI: 1.43-2.27); non-AD dementias, 1.32 (95% CI: 0.92-1.88), and all dementias 1.59 (95% CI: 1.26-2.01). For low and medium versus high education level, the RRs were: AD 1.44 (95% CI: 1.24-1.67); non-AD 1.23 (95% CI: 0.94-1.61), and all dementias 1.33 (95% CI: 1.15-1.54). These results confirm that low education may be a risk factor for dementia, especially for AD.

Recognition and treatment of Alzheimer's disease: a case-based review

Early recognition and treatment initiation are pivotal in managing Alzheimer's disease (AD). Once a diagnosis of AD is made, a treatment plan is developed and should include treatment initiation with cholinesterase inhibitors (ChEIs) to improve cognition, management of comorbid conditions, and treat behavioral symptoms. Caregiver compliance is integral to AD treatment success. The purpose of this report is to present two real case studies of "suspected" AD or related dementia and stress the significance of early and accurate diagnosis in disease management. In case 1, a caregiver reports gradual but progressive loss of memory, and the patient himself complains of memory impairment. Neuroimaging analysis confirms "typical " AD. In case 2, initiation of ChEI therapy is followed by substantial clinical improvement in the face of a complex medical picture, and neuroimaging revealing more neurodegenerative changes than could be accounted for by "pure" AD.

Correcting the 3MS for bias does not improve accuracy when screening for cognitive impairment or dementia

We investigated the effects of correcting for demographic biases on the sensitivity and specificity of the Modified Mini Mental Status Exam (3MS) using a sample of English-speaking older adults (N=8901) from the Canadian Studies of Health and Aging. The sensitivity and specificity of the original 3MS were compared to the 3MS regression-adjusted for the influence of demographic variables and then to 3MS percentiles based on published normative data with age and education corrected cutoff scores. According to receiver operating characteristic curve analyses, the regression-adjusted 3MS was no more accurate than the original 3MS when screening for dementia, and it was less accurate when screening for cognitive impairment. The use of 3MS percentiles based on normative data with age and education corrected cut-off points were less accurate than the original 3MS when screening for both cognitive impairment and when screening for dementia.