Clinical correlates of functional performance in community-dwelling Chinese older persons with mild cognitive impairment

ABSTRACTBackground: Increasing evidence suggests that functional impairment can be detected in older persons with mild cognitive impairment (MCI). This study explores the functional profiles and the clinical correlates of a population-based sample of Chinese older persons with MCI in Hong Kong.Methods: A random sample of 765 Chinese elderly subjects without dementia was recruited, of which 389 were elderly normal controls (Clinical Dementia Rating = 0), and 376 had questionable dementia (CDR = 0.5). The latter were categorized into an MCI group (n = 291) and a very mild dementia (VMD) group (n = 85). Their functional performances were measured and compared with the normal controls (NC). Multiple regression analyses investigated the associations between functional scores (Disability Assessment in Dementia) and clinical correlates (cognitive test scores, neuropsychiatric symptoms and motor signs) in the NC subjects and cognitively impaired subjects.Results: Subjects with MCI had intermediate functional performance between the NC and those with VMD. Regression analyses revealed that lower scores of cognitive tests (delayed recall and categorical verbal fluency tests), apathy, aberrant motor symptoms and parkinsonism features were associated with lower functional scores in clinically non-demented subjects. Functional scores had no correlation with age, education and medical illness burden.Conclusion: Neuropsychiatric symptoms and parkinsonism features were associated with functional impairment in the clinically non-demented elderly in the community. Assessment of these should be incorporated in the evaluation of older persons for early cognitive impairment.     

Predictors of future cognitive decline in persons with mild cognitive impairment

This study sought first to identify individual items of the Mini-Mental State Examination (MMSE) and demographic variables at baseline that predicted the trajectories of cognitive change among patients with mild cognitive impairment (MCI), and second to quantify the risk of cognitive decline in such patients based on their pattern of failure of MMSE items. 187 MCI patients were evaluated serially with the MMSE for up to 3.5 years. Patients who followed a declining cognitive trajectory differed from the stable reference group in their baseline profile of MMSE test performance. Patient age and performance on delayed recall, constructional praxis, attention, and orientation to time and floor predicted future cognitive decline with good accuracy (79.9%) and specificity (86.4%), and moderate sensitivity (67.2%). These results are presented in the form of a simple clinical tool for quantifying risk of future cognitive decline in MCI.     

Cognitive training for persons with mild cognitive impairment

Recent randomized control trials and meta-analyses of experimental studies indicate positive effects of non-pharmacological cognitive training on the cognitive function of healthy older adults. Furthermore, a large-scale randomized control trial with older adults, independent at entry, indicated that training delayed their cognitive and functional decline over a five-year follow-up. This supports cognitive training as a potentially efficient method to postpone cognitive decline in persons with mild cognitive impairment (MCI). Most of the research on the effect of cognitive training in MCI has reported increased performance following training on objective measures of memory whereas a minority reported no effect of training on objective cognitive measures. Interestingly, some of the studies that reported a positive effect of cognitive training in persons with MCI have observed large to moderate effect size. However, all of these studies have limited power and few have used long-term follow-ups or functional impact measures. Overall, this review highlights a need for a well-controlled randomized trial to assess the efficacy of cognitive training in MCI. It also raises a number of unresolved issues including proper outcome measures, issues of generalization and choice of intervention format.     

Characteristic profiles of instrumental activities of daily living in Chinese older persons with mild cognitive impairment

Increasing evidence suggests that performance of the instrumental activities of daily living (IADL) can be impaired at the mild cognitive impairment (MCI) stage. Our study aimed at investigating the profiles of functional impairment in Chinese subjects with MCI. Subjects with MCI were categorized into single-domain amnestic MCI (a-MCI) (n=54) and multiple-domain amnestic MCI (md-MCI) (n=93) groups. Their functional scores of Disability Assessment of Dementia (DAD) were compared with those of cognitively normal elderly controls (NC) (n=78) and those with mild Alzheimer's disease (AD) (n=85).Subjects with md-MCI had intermediate performance in IADL between the NC and those with mild AD. Subjects with a-MCI had functional scores similar to those of normal controls. Age, education, and global cognitive test scores were not associated with functional scores in MCI subjects. Our results demonstrated that Chinese older persons with md-MCI had impairment in IADL, as compared to NC and subjects with a-MCI. This finding suggests that assessment of IADL should be incorporated in the clinical evaluation of MCI.     

What is mild cognitive impairment? Variations in definitions and evolution of nondemented persons with cognitive impairment

Numerous studies have endeavoured to explore the nature of cognitive impairment in nondemented elderly persons. Comparison of this literature is hampered by huge variations in criteria and methodology. Despite these limitations, there are repeated reports that nondemented persons with cognitive impairment have a higher chance of progressing to dementia. Evidence also indicates higher mortality in cognitively impaired persons but there is also a chance of improvement in cognition over time. The current paper provides an overview of the various concepts and criteria proposed for cognitive impairment in nondemented persons, discusses some of the problems with current research in this field, and presents some of the findings concerning the evolution of cognitive impairment in relation to dementia, mortality and cognitive improvement.     

Inspection time in non-demented older adults with mild cognitive impairment

The aim of this study was to examine inspection time (IT) performance in older adults with mild cognitive impairment (MCI), who are at higher risk of developing further cognitive decline or dementia. IT is described as an index of speed of informational intake. IT correlates with measures of fluid intelligence and is possibly a marker for the integrity of the cholinergic system of the brain. IT may therefore be useful in aiding the diagnosis of early-stage progressive cognitive impairment. The current study compares IT in 28 people with MCI to 28 age, gender and education-matched controls. The computer-based, visual IT task required participants to discriminate between two visual stimuli that were presented for brief periods. Participants' IT performance was compared to their performance on cognitive and memory tasks. Group comparison showed that participants with MCI performed significantly worse on IT than controls and was not affected by years of education. In combination with other clinical, neuropsychological and biological tests, IT may be a useful assessment tool for improving the identification of older adults at risk for clinically relevant cognitive decline.     

Clinical outcomes in older surgical patients with mild cognitive impairment

Introduction

Older adults, including those with mild cognitive impairment (MCI), are increasingly undergoing surgery.

Improvement of episodic memory in persons with mild cognitive impairment and healthy older adults: evidence from a cognitive intervention program

The efficacy of cognitive training was assessed in persons with mild cognitive impairment (MCI) and persons with normal cognitive aging. Forty-seven participants were included in this study: 28 with MCI and 17 controls. Twenty-one participants received intervention (20 MCI and 9 controls) and 16 participants (8 MCI and 8 controls) received no intervention (waiting-list group). The intervention focused on teaching episodic memory strategies. Three tasks of episodic memory (list recall, face-name association, text memory) were used as primary outcome measures. Results were analyzed using analyses of variance. The intervention effect (pre- and post-intervention difference) was significant on two of the primary outcome measures (delayed list recall and face-name association). A significant pre-post-effect was also found on measures of subjective memory and well-being. There was no improvement in the performance of groups of individuals with MCI and normal elderly persons who did not receive the intervention. These results suggest that persons with MCI can improve their performance on episodic memory when provided with cognitive training.     

Olfactory identification and incidence of mild cognitive impairment in older age

CONTEXT: Mild cognitive impairment (MCI) is often a precursor to Alzheimer disease, but knowledge about factors that predict its development is limited. OBJECTIVE: To test the hypothesis that impaired odor identification is related to increased risk of incident MCI. DESIGN: Longitudinal cohort study. SETTING: Academic research. PARTICIPANTS: Subjects were 589 community-dwelling older persons without cognitive impairment at study baseline, at which time odor identification was assessed using the 12-item Brief Smell Identification Test (mean +/- SD score, 9.3 +/- 1.9). MAIN OUTCOME MEASURES: Incidence of MCI and rate of decline in cognitive function. RESULTS: During annual observation of up to 5 years, 177 subjects developed MCI. In a proportional hazards model adjusted for age, sex, and education, odor identification score predicted development of MCI (relative risk, 1.15; 95% confidence interval, 1.07-1.23), with risk increased by 50% in persons with below-average (score of 8 [25th percentile]) compared with above-average (score of 11 [75th percentile]) odor identification scores. Results were not substantially changed in subsequent analyses that controlled for level of cognitive function or disability, presence of stroke, or smoking status at baseline or that required MCI to persist for at least 1 year. Impaired odor identification was also associated with a lower level of global cognition at baseline and with more rapid decline in episodic memory, semantic memory, and perceptual speed. CONCLUSION: Among older persons without manifest cognitive impairment, difficulty in identifying odors predicts subsequent development of MCI.     

Impact of novelty and type of material on recognition in healthy older adults and persons with mild cognitive impairment

The goal of this study was to assess the effect of novelty on correct recognition (hit minus false alarms) and on recollection and familiarity processes in normal aging and amnestic mild cognitive impairment (MCI). Recognition tasks compared well-known and novel stimuli in the verbal domain (words vs. pseudowords) and in the musical domain (well-known vs. novel melodies). Results indicated that novel materials associated with lower correct recognition and lower recollection, an effect that can be related to its lower amenability to elaborative encoding in comparison with well-known items. Results also indicated that normal aging impairs recognition of well-known items, whereas MCI impairs recognition of novel items only. Healthy older adults showed impaired recollection and familiarity relative to younger controls and individuals with MCI showed impaired recollection relative to healthy older adults. The recollection deficit in healthy older adults and persons with MCI and their impaired recognition of well-known items is compatible with the difficulty both groups have in encoding information in an elaborate manner. In turn, familiarity deficit could be related to impaired frontal functioning. Therefore, novelty of material has a differential impact on recognition in persons with age-related memory disorders.     

Insulin and sex interactions in older adults with mild cognitive impairment

Alzheimer's disease (AD) and other dementias are likely preceded by a protracted preclinical state. Thus, identification of biomarkers that signal potential points of intervention during this prodromal phase (during which patients are largely able to compensate for their cognitive deficits) is of paramount importance. Insulin is a pancreatic hormone with potent central nervous system effects, and insulin dysregulation has been implicated in the pathogenesis of both AD and vascular dementia. The aim of the current study was to determine whether circulating insulin differs as a function of mild cognitive impairment (MCI) diagnosis, and whether this relationship is mediated by sex and apolipoprotein E (APOE) genotype. A sample of 549 nondemented participants aged 65 and over from the Adult Changes in Thought community-based cohort underwent cognitive testing and blood draw to determine fasting levels of plasma insulin. Subjects were categorized as having normal cognitive functioning, amnestic MCI, or nonamnestic MCI. Results showed that the relationship between insulin and diagnostic category is moderated by sex, such that men with nonamnestic or amnestic MCI have higher fasting plasma insulin than cognitively normal men, while women with amnestic MCI have lower fasting plasma insulin than cognitively normal women. Exploratory analyses suggest that APOE ε4 genotype may further influence the relationship between sex and insulin. Future research will help determine whether insulin dysregulation results in differential effects on vascular function and AD pathology as a function of sex and/or APOE genotype.     

Task switching capacities in persons with Alzheimer's disease and mild cognitive impairment

Task switching is an executive capacity that relies on a set of separate components implicating a fronto-parietal network of brain areas. In the present study, different components implicated in task switching were assessed in persons with Alzheimer's disease (AD), persons with mild cognitive impairment (MCI), and their matched healthy controls. The procedure implicated presentation of a two-digit stimulus, and task switching involved either conceptual or spatial switching. Global switching was measured by comparing blocks that involved non-switch trials to blocks that included switch trials, whereas local switching was measured by comparing performance across single trials in the switch blocks. Furthermore, the paradigm measured practice effects. Persons with AD showed larger local and global switch cost than healthy controls suggesting that their deficits encompass both reconfiguration of new action sets and maintenance of potentially relevant tasks within working memory. Importantly, the deficit was large in spatial switching but negligible in the conceptual condition. Persons with MCI only showed global switching impairment, suggesting a deficit restricted to the concurrent maintenance of two relevant task sets, and as in AD, this impairment was limited to spatial switching. Interestingly, persons with MCI, but not AD patients, improved their switching capacities upon practice. These findings indicate that switching deficit is selective in both MCI and AD persons, and is thus supportive of the notion that different mechanisms are involved in task switching. The pattern across condition is coherent with a continuum between those two clinical groups.     

老年人轻度帕金森病样体征与轻度认知功能损害的关系

目的:比较轻度帕金森病样体征(mild parkinsonian signs,MPS)和无MPS老人的轻度认知功能损害(mildcognitive impairment,MCI)患病情况,探讨MPS与MCI间的关系。方法:以506名大于70岁老年人为研究对象,使用国际通用帕金森病统一评分量表(The unified Parkinson's disease rating scale,UPDRS)第Ⅲ部分缩写版本评定MPS。将研究对象分为MPS组和无MPS组,分析MPS患病的危险因素及MCI患病情况。结果:MPS组较无MPS组的年龄大,患糖尿病及MCI比例高。结论:MPS与MCI的关系密切,不同类型的MPS对MCI的发病影响不同。     

An analysis of systems of classifying mild cognitive impairment in older people

OBJECTIVE: Over the past two decades, a number of systems have been developed for the classification of cognitive and behavioural abnormalities in older people, in order that individuals at high risk of developing neurodegenerative disease, particularly Alzheimer's disease, may be identified well before the disease manifests clinically. This article critically examines the inclusion and exclusion criteria of a number of such classification systems, to determine the effect that variations in criterion may have on clinical, behavioural and neuroimaging outcomes reported from older people with mild cognitive impairment. METHOD: Qualitative review of the literature describing systems of classifying mild cognitive impairment, and outcomes from clinical, behavioural, neuroimaging and genetic studies of older people with mild cognitive impairment. RESULTS: The exclusion and inclusion criteria for these classification systems vary markedly, as do the design of studies upon which the validity of these systems has been assessed. Minor changes to individual exclusion/inclusion criterion may result in substantial changes to estimates of the prevalence and clinical outcome of mild cognitive impairment, while inadequate experimental design may act to confound the interpretation of results. CONCLUSIONS: As a result of these factors, accurate and consistent estimates of the outcome of mild cognitive impairments in otherwise healthy older people are yet to be obtained. On the basis of this analysis of the literature, optimal criteria via which accurate classifications of mild cognitive impairment can be made in future are proposed.