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.     

Mild cognitive impairment

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

Mild cognitive impairment and vascular cognitive impairment in stroke patients

In 150 older stroke patients (>75) without dementia, the proportion of people meeting different criteria for early cognitive impairment varied from 17% to 23% depending upon the individual criteria used. Given this large disparity, prospective studies to clarify the utility of different criteria as a predictor of subsequent dementia are a priority.     

帕金森病轻度认知损害

轻度认知损害是帕金森病最为常见的非运动症状之一,是影响帕金森病患者日常生活活动能力的主要因素.轻度认知损害是介于正常老龄化与痴呆之间的过渡阶段,一般生活能力保持良好、发生轻度认知损害的帕金森病患者被称为帕金森病轻度认知损害,其临床特征可表现为不同认知领域损害,如工作记忆和(或)注意力、执行能力、言语、记忆力及视空间能力障碍等.在本文中,我们通过文献复习从流行病学、病理学、临床表现特点,以及辅助检查及诊断标准等方面对帕金森病轻度认知损害进行概述.     

Mild cognitive impairment: animal models

Mild cognitive impairment (MCI) is an aspect of cognitive aging that is considered to be a transitional state between normal aging and the dementia into which it may convert. Appropriate animal models are necessary in order to understand the pathogenic mechanisms of MCI and develop drugs for its treatment. In this review, we identify the features that should characterize an animal model of MCI, namely old age, subtle memory impairment, mild neuropathological changes, and changes in the cholinergic system, and the age at which these features can be detected in laboratory animals. These features should occur in aging animals with normal motor activity and feeding behavior. The animal models may be middle-aged rats and mice, rats with brain ischemia, transgenic mice overexpressing amyloid precursor protein and presenilin 1 (tested at an early stage), or aging monkeys. Memory deficits can be detected by selecting appropriately difficult behavioral tasks, and the deficits can be associated with neuropathological alterations. The reviewed literature demonstrates that, under certain conditions, these animal species can be considered to be MCI models, and that cognitive impairment in these models responds to drug treatment.     

帕金森病轻度认知损害

认知功能障碍是帕金森病较为常见的非运动症状,影响帕金森病患者生活质量、增加照料者负担。帕金森病认知功能障碍可以表现为轻度认知损害,也可以表现为痴呆。帕金森病轻度认知损害见于疾病早期,随着病情进展发病率逐渐升高,可进展为帕金森病痴呆。帕金森病轻度认知损害的诊断标准包括纳入标准、排除标准和损害水平判断。非药物治疗如运动锻炼和认知行为疗法可以改善帕金森病轻度认知损害症状,其药物治疗尚待进一步研究。     

帕金森病伴轻度认知功能障碍的研究进展

帕金森病伴发的轻度认知功能障碍，对患者的基本生活功能影响较小，但往往会演变成 帕金森痴呆，从而显著影响患者的生存质量及预后。因此，了解这一疾病，并对其进行早期干预具有十 分重要的意义。现从帕金森病轻度认知功能障碍的定义、临床表型、诊断标准、鉴别诊断、发病机制、危 险因素及治疗等方面进行综述，为相关研究提供参考。     

Mild cognitive impairment and cognitive reserve in Parkinson's disease

Patients with Parkinson’s disease (PD) typically present with motor symptoms, but non-motor symptoms, including cognitive impairment, autonomic dysfunction and neuropsychiatric symptoms, are usually also present, when looked for carefully. The objective of this paper is to provide an up-to-date, comprehensive review of two undecided issues about cognitive impairment in PD patients without dementia: the concept of Mild Cognitive Impairment (MCI) and the concept of Cognitive Reserve (CR). Empirical findings support the value of the concept of MCI in this population, from the early untreated stages onwards. Further studies are needed to establish 1) the clinical-neuroimaging characteristics of MCI subtypes in PD, in comparison to those MCI subtypes in patients without PD; 2) whether different types of MCI in PD are associated with different rates of cognitive decline during the progression of the disease. Preliminary empirical evidence also shows that education might exert a protective effect on cognitive decline in PD and that less educated subjects are at increased risk for developing dementia, lending support to the CR hypothesis, in this population as well. Further studies are necessary to investigate how CR modulates cognitive decline in PD and other frontal-subcortical disorders, e.g. by identifying possible differential effects of CR on different cognitive domains.     

Mild cognitive impairment: focus on diagnosis

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

Mild cognitive impairment: a cross-national comparison

OBJECTIVE: The main aim of this collaborative study was to assess the comparability of the most commonly used criteria for mild cognitive impairment (MCI) by comparing the cognitive performance of patients with MCI from the Mayo Clinic (USA) and the Karolinska Institutet (Sweden). METHODS: Standardised neuropsychological test scores were used to compare the two samples from the two institutions with regard to the number of cognitive domains in which performance was below 1.5 SD. Possible predictors for the conversion from MCI to Alzheimer's disease (AD) were assessed. RESULTS: When the two institutions were considered together in the Cox proportional hazard model, the number of affected cognitive domains below 1.5 SD was a significant predictor of time to AD diagnosis with age, education, and APOE epsilon4 genotype entered into the same model as covariates. The number of affected cognitive areas remained as a significant predictor when the institutions were considered separately. The logistic regression model of conversion to AD showed that only tests assessing learning and retention were predictors of developing AD. CONCLUSIONS: Differences in population as well as in methodology of case ascertainment as well as other aspects may account for the observed variability between samples of patients with MCI. The number of impaired cognitive factors at baseline can predict the progression from MCI to AD. Furthermore, tests assessing learning and retention are the best predictors for progression to AD.     

Mild cognitive impairment represents early-stage Alzheimer disease

BACKGROUND: Mild cognitive impairment (MCI) is considered to be a transitional stage between aging and Alzheimer disease (AD). OBJECTIVE: To determine whether MCI represents early-stage AD by examining its natural history and neuropathologic basis. DESIGN: A prospective clinical and psychometric study of community-living elderly volunteers, both nondemented and minimally cognitively impaired, followed up for up to 9.5 years. Neuropathologic examinations were performed on participants who had undergone autopsy. SETTING: An AD research center. PARTICIPANTS: All participants enrolled between July 1990 and June 1997 with Clinical Dementia Rating (CDR) scores of 0 (cognitively healthy; n = 177; mean age, 78.9 years) or 0.5 (equivalent to MCI; n = 277; mean age, 76.9 years). Based on the degree of clinical confidence that MCI represented dementia of the Alzheimer type (DAT), 3 subgroups of individuals with CDR scores of 0.5 were identified: CDR 0.5/DAT, CDR 0.5/incipient DAT, and CDR 0.5/uncertain dementia. MAIN OUTCOME MEASURE: Progression to the stage of CDR 1, which characterizes mild definite DAT. RESULTS: Survival analysis showed that 100% of CDR 0.5/DAT participants progressed to greater dementia severity over a 9.5-year period. At 5 years, rates of progression to a score of CDR 1 (or greater) for DAT were 60.5% (95% confidence interval [CI], 50.2%-70.8%) for the CDR 0.5/DAT group, 35.7% (95% CI, 21.0%-50.3%) for the CDR 0.5/incipient DAT group, 19.9% (95% CI, 8.0%-31.8%) for the CDR 0.5/uncertain dementia group, and 6.8% (95% CI, 2.2%-11.3%) for CDR 0/controls. Progression to greater dementia severity correlated with degree of cognitive impairment at baseline. Twenty-four of the 25 participants with scores of CDR 0.5 had a neuropathologic dementing disorder, which was AD in 21 (84%). CONCLUSIONS: Individuals currently characterized as having MCI progress steadily to greater stages of dementia severity at rates dependent on the level of cognitive impairment at entry and they almost always have the neuropathologic features of AD. We conclude that MCI generally represents early-stage AD.     

Mild cognitive impairment: making headway by stepping backwards.

Mild cognitive impairment (MCI) is a prevalent medical problem and the concept and term have become a catch-phrase for research and clinical practice. However, little is known about the most effective tools for a clinical diagnosis of MCI, its potential significance for individual patients and the best possible intervention--at least as long as MCI is considered as a diagnostic entity. We propose a simplified diagnostic and interventional algorithm for the detection and management of patients with MCI. We argue that MCI is so important, because it represents the closest call for an identification of treatable diseases or risk factors before the final manifestation of irreversible brain changes. Stepping backward by focussing on underlying disease processes and attempting causal interventions must be preferred to a mere symptomatic treatment of MCI as a preclinical form of Alzheimer's disease.     

Mild cognitive impairment is becoming more psychosocial

In recent years, researchers have underlined the need for more studies of early psychosocial interventions for patients with mild cognitive impairment (MCI) and early dementia (Moniz-Cook, Vernooij-Dassen, Woods, &; Orrell, 2011 Moniz-Cook, E., Vernooij-Dassen, M., Woods, B. and Orrell, M. 2011. Psychosocial interventions in dementia care research: the INTERDEM manifesto [Editorial]. Aging &; Mental Health, 15(3): 283–290. doi:10.1080/13607863.2010.543665[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]). In the last 10 years, MCI has become more ‘psychosocial’ and a starting point for professionals to help patients and their nearest ones to deal with their handicaps, to cope with a future that is insecure and gloomy, and to get prepared for the possibility of further decline and dependency. It is timely that Aging &; Mental Health is devoting this paper, a special section in this issue with contributions dealing with psychological and social aspects of MCI.