A typology of sub-clinical senescent cognitive disorder

Characteristics of the cognitive function transition and influencing factors among Chinese older people: An 8-year longitudinal study

BACKGROUND

Cognitive impairment among older people is an important public health problem in developing countries. Therefore, it is necessary to identify the subtypes of cognitive function among older people in China, and explore the transformation patterns and influencing factors.

METHODS

Longitudinal data from the China Health and Retirement Longitudinal Study (CHARLS) were used, and included 2140 women and 2049 men aged over 60 years. Latent profile and latent transition analysis (LPA&LTA) were used to identify subgroups and transitions between the profiles over time. Influencing factors were identified by multinomial logistic regression analysis.

RESULTS

According to the LPA model, three subgroups of cognitive function were identified: Cognitive Impairment, Mild Cognitive Impairment (MCI) and Normal Cognitive Function. Concurrently, >50 % of participants were likely to progress to MCI after seven years, whereas participants with cognitive impairment had a probability of 54.2 % of transitioning to a better cognitive profile. Older adults are less likely to experience cognitive improvement, higher levels of education affect changes in cognition, and having depression are at a lower risk of cognitive decline.

LIMITATIONS

Due to the incompleteness of the cognitive assessment and the large time span, there was a certain bias in the classification and analysis of latent cognitive profiles.

CONCLUSION

This study identified three latent profiles among Chinese older people and showed the stability and heterogeneity. It demonstrated the effects of higher age or levels of education, and depression on changes in cognitive function in older people.

A Latent Transition Analysis Model to Assess Change in Cognitive States over Three Occasions: Results from the Rush Memory and Aging Project

BACKGROUND

Conceptualizing cognitive aging as a step-sequential process is useful in identifying particular stages of cognitive function and impairment.

OBJECTIVE

We applied latent transition analysis (LTA) to determine 1) whether the underlying structure of cognitive profiles found at every measurement occasion are uniform across three waves of assessment, 2) whether class-instability is predictive of distal outcomes, and 3) whether class-reversions from impaired to non-impaired using latent modelling is lower than when using clinical criteria of mild cognitive impairment (MCI).

METHODS

A mover-stayer LTA model with dementia as a distal outcome was specified to model transitions of ten neuropsychological measures over three annual waves in the Rush Memory and Aging Project (n = 1,661). The predictive validity of the mover-stayer status for incident Alzheimer's disease (AD) was then assessed.

RESULTS

We identified a five-class model across the three time-points: Mixed-Domain Impairment, Memory-Specific Impairment, Frontal Impairment, Average, and Superior Cognition. None of the individuals in the Impairment classes reverted to the Average or Superior classes. Conventional MCI classification identified 26.4% and 14.1% at Times 1 and 2 as false-positive cases. "Movers" had 87% increased risk of developing dementia compared to those classified as "Stayers".

CONCLUSION

Our findings support the use of latent variable modelling that incorporates comprehensive neuropsychological assessment to identify and classify cognitive impairment.

Copolymer-1 enhances cognitive performance in young adult rats

Cognitive impairment is a dysfunction observed as a sequel of various neurodegenerative diseases, as well as a concomitant element in the elderly stages of life. In clinical settings, this malfunction is identified as mild cognitive impairment. Previous studies have suggested that cognitive impairment could be the result of a reduction in the expression of brain-derived neurotrophic factor (BDNF) and/or immune dysfunction. Copolymer-1 (Cop-1) is an FDA-approved synthetic peptide capable of inducing the activation of Th2/3 cells, which are able to release BDNF, as well as to migrate and accumulate in the brain. In this study, we evaluated the effect of Cop-1 immunization on improvement of cognition in adult rats. For this purpose, we performed four experiments. We evaluated the effect of Cop-1 immunization on learning/memory using the Morris water maze for spatial memory and autoshaping for associative memory in 3- or 6-month-old rats. BDNF concentrations at the hippocampus were determined by ELISA. Cop-1 immunization induced a significant improvement of spatial memory and associative memory in 6-month-old rats. Likewise, Cop-1 improved spatial memory and associative memory when animals were immunized at 3 months and evaluated at 6 months old. Additionally, Cop-1 induced a significant increase in BDNF levels at the hippocampus. To our knowledge, the present investigation reports the first instance of Cop-1 treatment enhancing cognitive function in normal young adult rats, suggesting that Cop-1 may be a practical therapeutic strategy potentially useful for age- or disease-related cognitive impairment.

Differences in cognitive aging: typology based on a community structure detection approach

The current study investigated the extent and patterns of cognitive variability in younger and older adults. An important novelty of this study is the use of graph-based community structure detection analysis to map performance in a mixed population of 79 young and 76 older adults, without separating the age groups a-priori. We identified six subgroups, with distinct patterns of neuropsychological performance. The stability of the identified subgroups was confirmed by employing a cross-validation support vector machine based analysis. The majority of these subgroups comprised either young or older adults, confirming the expected role of aging in cognitive performance. In addition, we identified a subgroup of young and older adults who performed at a similar cognitive level of overall good cognitive performance with slightly decreased processing speed. This result showed that older age is not necessarily associated with general lower cognitive performance and that being young is not necessarily associated with superior cognitive performance. Moreover, cognitively better performing elderly had a significantly higher level of education attainment and higher crystallized intelligence than the other elderly, which suggests that older adults with higher cognitive reserve may be able to cope better with age-related neurobiological change.

Can Clinical Data Predict Progression to Dementia in Amnestic Mild Cognitive Impairment?

Background:

To determine whether clinical data obtained by history and physical examination can predict eventual progression to dementia in a cohort of elderly people with mild cognitive impairment.

Methods:

A prospective, longitudinal study of a cohort of elderly subjects with amnestic Mild Cognitive Impairment (MCI). Ninety subjects meeting the criteria for amnestic MCI were recruited and followed annually for an average of 3.3 years. Main outcome measure was the development of dementia determined by clinical assessment with confirmatory neuropsychological evaluation.

Results:

Fifty patients (56%) developed dementia on follow-up. They were older, had lower Mini-mental status exam (MMSE) scores and a shorter duration of symptoms at the time of first assessment. Multivariate logistic regression analysis identified age at symptom onset as the only clinical parameter which distinguished the group that deteriorated to dementia from the group that did not. The odds ratio for age was 1.1 (confidence interval 1.04 - 1.18).

Conclusions:

Patients presenting with amnestic MCI insufficient for the diagnosis of dementia are at high risk of developing dementia on follow-up. In our cohort, 56% were diagnosed with dementia over an average period of 5.9 years from symptom onset. The only clinical predictor for the eventual development of dementia was older age at symptom onset. Clinical features alone were insufficient to predict development of dementia.

Mild cognitive impairment: an epidemiological perspective

Mild cognitive impairment (MCI) refers to cognitive impairment that is assumed to be due to pathological central nervous system processes, but which interacts with normal aging-related changes. Epidemiological studies conducted in the general population have been able to examine more heterogeneous forms of this disorder than clinical studies, and have also been able to provide early estimations of population incidence and prevalence. Large differences in case identification procedures and sampling methods have led to considerable divergence in the rates of prevalence reported, which ranged from 1% to 29%. Suggested improvements in the definition of MCI have led to an upward adjustment of prevalence rates in most studies, giving between 5% and 29%. Incidence is estimated as 8 to 58 new cases per thousand persons per year, and the probability of conversion from MCI to dementia is estimated at around 15%. The principal risk factors that have been identified so far for MCI using regression models applied to general population data are age, education, race, medicated hypertension, infarcts, white matter lesions, depression, and apolipoprotein E4 (AP0E-4J allele. An etiological model derived from these studies indicates possible intervention points for future therapeutic strategies at the level of both clinical intervention and environmental exposure. There is, however, a clear need for epidemiological studies that take into account a broader range of risk factors than those studied to date, which have focused principally on known risk factors for dementia.

Heterogeneity of cognitive aging in Brazilian normal elderls

With aging, several cognitive skills inevitably decline. However, cognitive losses do not occur homogenously in all elderly people, differing in number and severity of affected cognitive functions. These differences could be exacerbated by socioeconomic differences in a developing country like Brazil.

Clinical validity of Fuld Object Memory Evaluation to screen for dementia in a Chinese society

OBJECTIVES

Fuld Object Memory Evaluation (FOME) evaluates the episodic memory functions of encoding, storage, and recall across five recall trials and a delayed recall trial. This study examined the clinical validity of FOME as a screening tool for dementia in older Chinese adults.

METHOD

The psychometric properties and the discriminative power of FOME were examined in a convenience sample of 192 community-dwelling older individuals, of which 57 were diagnosed with dementia. The influence of age and education on the FOME performance was also estimated.

RESULTS

The test-retest reliability and parallel-form reliability of FOME were excellent, with Intraclass Correlation Coefficients ranging from 0.91-0.96. Good convergent validity of FOME was established with Mini-Mental State Examination (r(p) = 0.69-0.74), and the Memory subscale and the Initiation/Perseveration subscale of Dementia Rating Scale (r(p) = 0.63-0.74). The FOME total retrieval (TR) score and delayed recall (DR) score demonstrated good discriminative power in differentiating dementia from normal cognitive functioning, with area under the curve values of 0.97 and 0.93 respectively. The optimal cut-off scores suggested for TR and DR were 31 (93% sensitivity, 90 specificity) and 7 (91% sensitivity, 82% specificity), respectively. The performance of the FOME was not influenced by the educational level.

CONCLUSIONS

The results suggest that the FOME is a reliable and valid instrument to screen for dementia in older community-dwelling Chinese adults. The absence of the effects of education on the assessment performance makes FOME a clinically useful instrument for older adults with limited education.

Diagnosis and treatment of dementia: 3. Mild cognitive impairment and cognitive impairment without dementia

BACKGROUND

Mild cognitive impairment and cognitive impairment, no dementia, are emerging terms that encompass the clinical state between normal cognition and dementia in elderly people. Controversy surrounds their characterization, definition and application in clinical practice. In this article, we provide physicians with practical guidance on the definition, diagnosis and treatment of mild cognitive impairment and cognitive impairment, no dementia, based on recommendations from the Third Canadian Consensus Conference on the Diagnosis and Treatment of Dementia, held in March 2006.

METHODS

We developed evidence-based guidelines using systematic literature searches, with specific criteria for study selection and quality assessment, and a clear and transparent decision-making process. We selected studies published from January 1996 to December 2005 that had mild cognitive impairment or cognitive impairment, no dementia, as the outcome. Subsequent to the conference, we searched for additional articles published between January 2006 and January 2008. We graded the strength of evidence using the criteria of the Canadian Task Force on Preventive Health Care.

RESULTS

We identified 2483 articles, of which 314 were considered to be relevant and of good or fair quality. From a synthesis of the evidence in these studies, we made 16 recommendations. In brief, family physicians should be aware that most types of dementia are preceded by a recognizable phase of mild cognitive decline. They should be familiar with the concepts of mild cognitive impairment and of cognitive impairment, no dementia. Patients with these conditions should be closely monitored because of their increased risk for dementia. Leisure activities, cognitive stimulation and physical activity could be promoted as part of a healthy lifestyle in elderly people and those with mild cognitive impairment. Vascular risk factors should be treated optimally. No other specific therapies can yet be recommended.

INTERPRETATION

Physicians will increasingly see elderly patients with mild memory loss, and learning an approach to diagnosing states such as mild cognitive impairment is now warranted. Close monitoring for progression to dementia, promotion of a healthy lifestyle and treatment of vascular risk factors are recommended for the management of patients with mild cognitive impairment.

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.

A new Brief computerized cognitive screening battery (CompCogs) for early diagnosis of Alzheimer's disease

Screening tests for early diagnosis of dementia are of great clinical relevance. The ideal test set must be brief and reliable, and should probe cognitive components impaired in Alzheimer’s disease (AD).

Neuropsychological Subgroups of Cognitively-Impaired-Not-Demented (CIND) Individuals: Delineation, Reliability, and Predictive Validity

The objectives of the present investigation were to determine whether subgroups of Cognitively-Impaired-Not-Demented (CIND) individuals with distinct neuropsychological profiles exist in two independent samples, and whether subgroup membership is related to diagnostic outcome over periods of 2 to 5 years. A series of cluster analyses was performed on ipsative factor z-scores derived from principal component analyses. Five subgroups were identified in the Base Sample (n = 461): Verbal Dysfunction, Verbal/Visuospatial Dysfunction, Memory/Verbal Dysfunction, Memory Dysfunction, and Visuospatial Dysfunction. This five-cluster solution was replicated in an independent sample of CIND individuals (n = 166). The highest rates of conversion to dementia were observed in the Memory Dysfunction and Memory/Verbal Dysfunction subgroups. The Verbal Dysfunction subgroup was most likely to show improvement in cognitive status. The cognitive heterogeneity of the CIND condition must be taken into account in future research focusing on the early identification of dementia.

Preclinical evidence of Alzheimer changes in progressive mild cognitive impairment: a qualitative and quantitative SPECT study

OBJECTIVES

Baseline brain single-photon emission computed tomography (SPECT) can predict mild cognitive impairment (MCI) patients at risk for progressive MCI (PMCI).

METHODS

Twenty-eight subjects [12 MCI, 6 with probable Alzheimer's Disease (AD), and 10 normal subjects] underwent baseline brain SPECT and were clinically followed for a mean period of 36 months.

RESULTS

Of 12 MCI patients, 6 progressed to PMCI and 6 remained stable. Baseline SPECT identified asymmetric perfusion reduction in the parahippocampus (-5%), lateral parietal (-8%), and posterior cingulate (-11%) cortices--reductions consistent with that of mild AD--in five of the six PMCI patients. Significant perfusion reduction was observed particularly in the frontal cortices of probable AD when compared with PMCI (P < 0.05).

CONCLUSION

Baseline SPECT can identify brain perfusion abnormalities among patients with MCI for progression to PMCI. This imaging modality may aid in MCI treatment stratification.

VITA: subtypes of mild cognitive impairment in a community-based cohort at the age of 75 years

BACKGROUND

Mild cognitive impairment (MCI) is defined to diagnose prodromal dementia and prodromal Alzheimer dementia, in particular.

OBJECTIVE

The main aim of this study is to identify subtypes of MCI in comparison to the frequency of Petersen's MCI-amnestic in an elderly age-cohort.

PARTICIPANTS

The study is based on the cross sectional data from the Vienna-Transdanube-Aging (VITA) study. The data refer to the age cohort of 592 individuals at age 75 to 76 years who completed extensive neuropsychological examination.

RESULTS

Dementia was present in 15 subjects (2.5%, CI: 1.4-4.1). 141 subjects (23.8%, CI: 20.4-27.5) of the entire age cohort 75 (n = 592) showed cognitive impairment without dementia concerning one or more cognitive functions (1.5 SD paradigm). These subjects were assigned to three subtypes of MCI: Selective Memory Impairment: n = 22 (3.7%, CI: 2.3-5.6), Memory Impairment+Non-Memory Impairment: n = 31 (5.2%, CI: 3.6-7.4) and Non-Memory Impairment: n = 88 (14.9%, CI: 12.1-18.0).

CONCLUSIONS

The frequency of MCI-amnestic, the so-called prestage of AD according to Petersen, was very low (0.5%, CI: 0.1-1.5) compared to the estimated incidence rates of AD at this age. Established criteria of MCI could be modified in order to include a higher percentage of high-risk subjects for later developing Alzheimer dementia.

Mediterranean diet and cognitive decline

OBJECTIVE

To investigate the possible role of diet in age-related cognitive decline (ARCD) and cognitive impairment of both degenerative (Alzheimer's disease, AD) and vascular (vascular dementia, VaD) origin.

DESIGN

Literature review.

RESULTS

In an elderly population of southern Italy with a typical Mediterranean diet, high energy intake of monounsaturated fatty acids (MUFA) appeared to be associated with a high level of protection against ARCD. In addition, dietary fat and energy in the elderly seem to be risk factors, while fish consumption and cereals are found to reduce the prevalence of AD in European and North American countries. Finally, the relative risk of dementia (AD and VaD) was lower in the subjects of a French cohort who drank three or four glasses of red wine each day compared with total abstainers.

CONCLUSION

Essential components of the Mediterranean diet--MUFA, cereals and wine--seem to be protective against cognitive decline. As such, dietary antioxidants and supplements, specific macronutrients of the Mediterranean diet, oestrogens and anti-inflammatory drugs may act synergistically with other protective factors, opening up new therapeutic interventions for cognitive decline.

Apolipoproteins E and C1 and brain morphology in memory impaired elders

Previous research has shown that polymorphisms of the apolipoproteins E ( APOE) and APOC1 represent genetic risk factors for dementia and for cognitive impairment in the elderly. The brain mechanisms by which these genetic variations affect behavior or clinical severity are poorly understood. We studied the effect of APOE and APOC1 genes on magnetic resonance imaging measures in a sample of 50 subjects with age-associated memory impairment. The APOE E4 allele was associated with reduced left hippocampal volumes and APOE*E3 status was associated with greater frontal lobe white matter volumes. However, no APOE effects were observed when analyses accounted for other potential confounding variables. The effects of APOC1 on hippocampal volumes appeared to be more robust than those of the APOE polymorphism. However, no modulatory effects on brain morphology outside the medial temporal lobe region were observed when demographic variables, clinical status, and other anatomical brain measurements were taken into consideration. Our results suggest that the role of the APOC1 polymorphism in brain morphology of the cognitively impaired elderly should be examined in further studies.

Cognitive Plasticity in Healthy, Mild Cognitive Impairment (MCI) Subjects and Alzheimer's Disease Patients: A Research Project in Spain

Cognitive plasticity, learning potential, and rehabilitation potential are new constructs, which are understood as expressions of neural plasticity. They are assessed through dynamic assessment (or testing-the-limits), using experimental test-training-posttest, a form of evaluation closely related to functional or stress testing in medicine. This research strategy has been used for increasing knowledge about several target populations with intellectual handicaps (socially mentally retarded, brain-impaired, schizophrenia patients, etc.), including older people whose fluid intellectual capacity has declined. Recently, cognitive plasticity has been applied to the study of dementia ( Baltes & Baltes, 1997 ), but there are very few other studies in this area. The basic objective of this research program is to test the extent to which learning potential can be a predictor of the course of dementia. The first specific objective of the research is to test whether learning can discriminate healthy people from those diagnosed with Mild Cognitive Impairment (MCI) and with Alzheimer's Disease (AD). In order to assess cognitive plasticity, a Battery of Learning Potential for Assessing Dementia (BEPAD) was developed, incorporating four tests for assessing visuo-spatial and verbal memory, executive function, and verbal fluency. Two hundred subjects participated in the study: 100 healthy elderly, 50 diagnosed with MCI and 50 with AD. All learning strategies included in the four tests making up the BEPAD appear to be effective: All three groups improved their performance in visual memory, verbal learning, and executive function.

Mild cognitive impairment

Mild cognitive impairment is an emerging term that encompasses the clinical state between elderly normal cognition and dementia. Controversy surrounds its characterization, implementation, and definition. Mild cognitive impairment is now the focus of natural history studies, biomarker studies, along with Alzheimer's disease prevention studies. The mild cognitive impairment stage may be the optimum stage at which to intervene with preventive therapies. Depending on the cohort source and definition, between 19 and 50% of mild cognitive impairment individuals progress to dementia (usually Alzheimer's disease) over 3 years. Despite controversy, progress has been achieved in defining risk factors for progression from mild cognitive impairment to dementia. New treatments to prevent development of Alzheimer's disease are targeting mild cognitive impairment as a treatment group and neurologists will increasingly be called upon to make this diagnosis.

Magnetization transfer ratio in mild cognitive impairment and dementia of Alzheimer's type

Almost half of the elderly subjects that are diagnosed with mild cognitive impairment (MCI) go on to develop dementia of Alzheimer's type (DAT) over a 5-year follow-up. MCI and DAT subjects show regional decreases in the volume of brain structures, which correlate with the cognitive decline among these groups. Volumetric changes are found more consistently in the DAT group than in the MCI group. Since not all MCI subjects demonstrate volumetric decline, we propose that the underlying changes in the structural integrity of the brain, measured using magnetization transfer ratio (MTR), may be used as an additional predictor for abnormal cognitive decline in the elderly. Magnetic resonance (MR) images were obtained in 15 DAT, MCI, and elderly control subjects. Using automatic tissue classification, the brain region of each MR volume was segmented into gray matter and white matter. Mean and standard error of the mean MTR measured within the gray matter was found to be significantly lower in the MCI (30.77 +/-0.29; P = 0.037) and the DAT (29.37 +/-0.41; P = 0.000) group compared to the control group (32.11 +/-0.20). The MTR of white matter was significantly lower only in the DAT group. The gray matter volume was significantly lower (P = 0.000) in the DAT (387.29 +/-26.04 cm(3)) group compared to controls (532.93 +/-20.53 cm(3)) and MCI (464.64 +/-16.93 cm(3)). No significant differences were found in the white matter volume between the three groups. We conclude that changes in MTR are measurable even in the absence of detectable volumetric changes in gray and white matter in the MCI group. Furthermore, MTR changes may present a novel MRI measure for the early diagnosis of dementia of Alzheimer's type.

Mild extrapyramidal signs and functional impairment in ageing

BACKGROUND

Little is known about the clinical significance of mild extrapyramidal signs (EPS) in elderly individuals. We investigated whether EPS are associated with functional impairment in older people with cognitive decline.

METHODS

A sub-group of 105 participants from the EUGERIA Study of Cognitive Ageing without Parkinson's disease or dementia, but with informant evidence of cognitive decline, were followed across three years and underwent neurological examination and assessment of mental health, cognition and functional capacity.

RESULTS

28.6% had at least one EPS (resting tremor, muscular rigidity or akinesia, of which rigidity was the most frequent). EPS presence was significantly associated with functional impairment after controlling for age and cognitive impairment (AAMI), although the association was reduced to borderline significance after further adjustment for depression and psychotropic medication use. There was evidence of colinearity between EPS and depression, possibly suggesting similar underlying mechanisms.

CONCLUSIONS

There is an association between mild EPS and functional impairment in older persons with evidence of cognitive decline, but free of dementia or Parkinson's disease.

Exposure to anaesthetic agents, cognitive functioning and depressive symptomatology in the elderly

BACKGROUND

Anaesthesia could provoke persistent alterations in specific cognitive domains in the elderly where ageing-related neuronal changes may exacerbate pharmacotoxic effects.

AIMS

To evaluate anaesthesia effects on the incidence of cognitive dysfunction after orthopaedic surgery in elderly patients.

METHOD

A total of 140 patients over the age of 64 years completed a full range of computerised cognitive tests. The study takes into account effects of pre-operative cognitive dysfunction, depressive symptomatology and ability to perform activities of daily living.

RESULTS

Postoperative cognitive decline persisted for up to 3 months in 56% of subjects. Dysfunction was limited to verbal, visuo-spatial and semantic abilities and secondary and implicit memory. Age, low educational level, pre-operative cognitive impairment or depression are risk factors.

CONCLUSIONS

Cognitive functions are not equally affected, type of impairment being determined by the risk factors described above and anaesthesia type.

Assessment of suspected dementia

At the Second Canadian Consensus Conference on Dementia (CCCD) (February, 1998), a group of neurologists, geriatricians, and psychiatrists met to consider guidelines for evaluation of dementia in Canada. This review paper formed a background paper for their discussion of dementia diagnosis. These experts from across the country concluded that diagnosis of suspected dementia cases continued to rest on skilled clinical assessment. Mental status exam, preferably in some quantifiable form, has become an essential part of the assessment. Selected laboratory tests are advisable in all cases (CBC, TSH, electrolytes, calcium, and glucose), but the CCCD continued to advise that CT scanning was mandatory only in selected cases where clinical findings pointed to another possibility besides Alzheimer's disease. The growing list of other diagnostic measures with potential usefulness in diagnosis of Alzheimer's disease or dementia in general was reviewed, but the evidence was judged as insufficient to support routine use of these tests by physicians. As new treatments for Alzheimer's disease become available, neurologists face new diagnostic challenges--differentiating Mild Cognitive Impairment, Frontotemporal dementias and Mixed dementias, and Lewy Body Dementia. Guidelines to aid in differential diagnosis are presented.

Screening for cognitive impairment and dementia in the elderly

OBJECTIVE

To review the evidence available to support or refute the recommendation to screen for cognitive impairment (cognitive deficits which do not affect daily function) and dementia in primary care.

DATA SOURCES

Medline search using terms listed at the end of this article; consultation with experts in the field; review of other published recommendations.

STUDY SELECTION

There were no articles which described a randomized controlled trial of screening versus no screening. Studies were therefore chosen which aided in the definition; natural history; interventions and outcomes including possible negative effects.

DATA SYNTHESIS

No systematic synthesis was performed. Background papers were circulated to a panel of experts prior to the Canadian Consensus Conference on Dementia and conclusions endorsed by consensus.

CONCLUSIONS

1. There is insufficient evidence to recommend for or against screening for cognitive impairment or dementia. (C); 2. Memory complaints should be evaluated and the individual followed to assess progression. (B); 3. When caregivers or informants describe cognitive decline in an individual, these observations should be taken very seriously; cognitive assessment and careful follow-up are indicated. (A) (See Appendix).

Preventing dementia

Primary prevention will become increasingly important as dementia prevalence increases and effective retardive therapies are developed. To date, only one randomized controlled trial (involving treatment of systolic hypertension) has demonstrated that the incidence of dementia can be reduced. Physicians should remain alert to possible secondary causes of dementia and correct these whenever possible. Primary and secondary prevention of stroke should reduce dementia related to cerebrovascular disease either directly or as a comorbid factor in Alzheimer's disease (AD). Epidemiological studies have revealed a number of risk factors for AD including genetic mutation, susceptibility genes, positive family history, Down's syndrome, age, sex, years of education, head trauma and neurotoxins. In case-control studies non-steroidal anti-inflammatory medication and estrogen replacement therapy appear to decrease the relative risk of developing AD. Further research to develop and test preventative therapies in AD and other dementias should be strongly encouraged.

Prediction of deterioration in mild cognitive disorder in old age--neuropsychological and neurochemical parameters of dementia diseases

In normal senescence, an age-related impairment of cognitive function is observed. The difficult clinical question is in which cases of mild cognitive impairment (MCI) will there be a rapid cognitive decline to a dementia syndrome. Two ways to improve prognosis are discussed: neuropsychological tests and analysis of neurochemical markers. First, the question is asked as to whether there are clusters of MCI. Longitudinal neuropsychological data from the Berlin Aging Study (BASE) are presented, a population-based sample of 516 subjects aged 70 to 103 years. There are clusters found that in part match those clusters, which have been identified by a study from Ritchie et al. in 1996. Especially, a cluster of 13.8% of the nondemented participants with a decline in memory performance is observed. The validation of clusters of cognitive performance and decline opens up the possibility of diagnosing distinctive subgroups of MCI to improve prognosis in old age. Second, the existing data concerning the diagnostic laboratory analysis for Alzheimer's disease (AD) are reviewed. Especially, data regarding nerve growth factor (NGF) are reported. In MCI, preliminary data show a correlation between the NGF serum level and cognitive performance. It can be concluded that the combined investigation of neuropsychological functions and cognitive decline, as well as laboratory measurement of neurochemical markers, might allow an improved prognosis for mental health in very old age.

Heterogeneity of cognitive profiles in aging: successful aging, normal aging, and individuals at risk for cognitive decline

Neuropsychological clinical decision-making is complicated by the fact that variability in test performance increases with advancing age. This research explores the presence of homogeneous subgroups in 120 neurologically healthy individuals, from 55 to 85 years of age. Subjects at risk for dementing diseases were diagnosed as Aging-Associated Cognitive Decline (AACD) and Mild Cognitive Impairment (MCI). Cluster analysis was applied on 11 neuropsychological variables assessing logical memory immediate recall and retention percentage, visual memory immediate recall and retention, conceptual thinking, naming, verbal fluency, constructional functions, motor speed, flexibility and finger tapping. Five clusters were extracted, one representing cognitively successfully aged, and two consisting of individuals with normal or average level of performance. One cluster was characterized by older subjects with difficulties in visual memory, visuoconstructional functions, and speed and attention, most of the younger subjects in the same cluster had a diagnosis of AACD or MCI. The fifth cluster represented individuals at risk for dementing diseases; most of them were diagnosed having AACD and more than half had a diagnosis of MCI. Age, activity and intellectual levels, and to a lesser degree education, were significantly related to the cluster solution. The present findings caution against treating samples of elderly individuals as homogeneous.

Cognitive decline in ageing: are AAMI and AACD distinct entities?

BACKGROUND

Two sets of research diagnostic criteria, age-associated memory impairment (AAMI) and ageing-associated cognitive decline (AACD), are widely used to describe mild cognitive decline in ageing. However, the extent to which the nosological entities they represent are similar or distinct is unclear.

METHODS

A sample of 111 participants without dementia but with informant evidence of cognitive decline were drawn from the EUGERIA Study of Cognitive Ageing, a population-based study in southern France. These participants were classified as either normal or with AAMI according to the criteria of Crook et al. (1986), then reclassified as normal or with AACD according to criteria recommended by Levy et al. (1994). Neuropsychological test scores were then compared in these two pairs of groups.

RESULTS

Particpants were classified as either normal (N=74) or with AAMI (N=37), then reclassified as normal (N=72) or with AACD (N=39). Only 20 (54%) of participants with AAMI simultaneously met criteria for AACD, and those with AACD showed more extensive cognitive impairment than those with AAMI.

CONCLUSIONS

Although there is a large overlap between AAMI and AACD, these findings suggest that AAMI and AACD refer to distinct clinical entities, the latter delineating a more severe state of impairment. This may be largely because AAMI is defined as impairment with reference to young normals, whereas AACD refers to impairment with respect to normal contemporaries.

Prevalence of mild cognitive impairment in an elderly community sample

The term "mild cognitive impairment" refers to cognitive deficits which exceed normal physiological aging processes, but do not fulfill the criteria for dementia. While recent studies indicate that the respective deficits can be reliably assessed, different diagnostic criteria have prevented a wide application of this diagnosis in clinical practice. The aims of the present study were (1) to assess the prevalence rates of four current diagnostic concepts and (2) to investigate mild cognitive impairment with respect to psychological and sociodemographic variables. Data from 202 probands recruited from the interdisciplinary longitudinal study on adult development were analyzed. On the time of examination, probands were between 60 to 64 years old and in a good health. The following prevalence rates were determined: 13.5% for age-associated memory impairment (AAMI), 6.5% for age-consistent memory impairment (ACMI), 1.5% for late-life forgetfulness (LLF), and 23.5% for aging-associated cognitive decline (AACD). Complaints of cognitive deficits were significantly correlated with higher scores on depression and neuroticism scales but with none of the neuropsychological measures. Reduced performance in neuropsychological tests was associated with a lower educational level and socioeconomic status. We conclude that the prevalence rates of mild cognitive impairment are highly dependent on the diagnostic criteria applied. In this respect the self-report of cognitive decline might be a less useful criteria. Longitudinal studies are warranted to further elucidate the predictive value of these diagnostic criteria.

Establishing the limits of normal cerebral ageing and senile dementias

Cognitive deterioration is so commonly observed in the elderly that it is considered by many to be an inevitable feature of the ageing process. Some researchers have proposed that the senile dementias are the inevitable end-point of this process, should the person live long enough. The differentiation of normal cerebral ageing from disease process is important in the selection of control groups for research, and also for clinical decision-making. In the latter context it is important to ask at what level of dysfunction intervention should occur, and whether this should be active or palliative. Cognitive change in the elderly is here considered from biological, neuropsychological and epidemiological viewpoints. Current research suggests that senile dementia is the result of the interplay of genetically determined disease processes, ageing-related decline which may be regulated at a cellular level, and neuronal repair and compensation mechanisms. Therefore, to debate whether dementia is simply an extension of a normal ageing process or not is probably too simplistic an approach.

Disability and cognitive impairment in the elderly

Disability and cognitive impairment show similar patterns of increasing frequency with ageing. A review of the published literature shows that there is a cross-sectional relationship between cognitive impairment and disability, independent of demographic, medical, and lifestyle factors. Some instrumental activities of daily living (IADL) items appear more specifically related to cognitive impairment, but cognition and functional impairment are distinct concepts requiring separate assessments. Subjects with low cognitive performances are at higher risk of functional impairment in the following years. Cognitive impairment as well as disability increase the risk of death and institutionalization. Preventive strategies could be directed against the risk factors of cognitive impairment and disability, and would aim to delay the onset of dementia. Prevention of disability associated with cognitive impairment needs further assessment in elderly community-dwellers. Further research is needed to better identify the specific areas cognition involved in the disablement process.