MILD COGNITIVE IMPAIRMENT

Late-Life Depression, Cognitive Impairment, and Relationship with Alzheimer's Disease

This narrative review aimed to explore the existing knowledge in order to examine the multiple forms of late-life depression (LLD) within a non-neurodegenerative or a neurodegenerative context, in particular Alzheimer's disease (AD). This review will first provide information about different pathogenic hypotheses proposed to describe LLD when it is not linked to a neurodegenerative context. Within the presentation of these syndromes, the literature reports thymic and cognitive specific features and highlights a common preponderance of cognitive impairment, and particularly executive. This review will also report data from research works that have addressed the role of depressive symptoms (DSs) in incidence of AD and mild cognitive impairment (MCI) conversion to AD. These findings support the claim that the relationship between DS (or LLD) and the cognitive decline encountered in AD can be of 2 types: (1) risk factor or (2) prodrome. They also support the hypothesis that the effect of DS on the incidence of AD can be identified between specific characteristics of these symptoms such as a very first apparition late in life, an increasing severity of DS, and a poor response to medical treatment. Finally, longitudinal and cross-sectional research will be presented, aiming to identify the predictive value of DS (or LLD) on AD incidence and/or conversion of MCI (and specifically amnestic MCI). This final section shows that specific features of LLD, such as being of early- or late-onset, can be considered as indices of AD incidence.

Lifestyle changes and outcomes of older adults with mild cognitive impairment: A 4-year longitudinal study

BACKGROUND

Longitudinal studies have shown that mild cognitive impairment (MCI) reverts to normal cognition (NC). However, we could not find any reports on the examination of changes in lifestyle activity patterns in older adults diagnosed with MCI and their outcomes, in a longitudinal study. We determined the changes in lifestyle activity patterns among older adults with MCI.

METHODS

The participants in this study were 769 community-dwelling older adults aged ≥65 years with MCI at baseline. Four years later, participants were categorized into reverters, maintainers, and converters who reverted from MCI to NC, maintained MCI, and had global cognitive impairment or Alzheimer disease, respectively. We used latent class analysis to classify changes in instrumental activities of daily living, and in cognitive, social, and productive activities of the participants. Subsequently, a multinomial logistic regression analysis was performed with reversion status and class membership as the dependent and independent variables, respectively.

RESULTS

The reversion rate of 769 participants was 33.3%. The reverters maintained multidomain lifestyle activities, converters discontinued multidomain lifestyle activities or were inactive, and maintainers maintained productive activities. According to the logistic regression analysis, the activity patterns of those who continued to engage in multidomain lifestyle activities and start activities, were more likely to help in reverting from MCI to NC (P < 0.05).

CONCLUSIONS

Community-dwelling older adults with MCI who continued their multidomain lifestyle activities were more likely to revert to NC. Even if it does not revert to NC, continuing productive activities is important to maintaining MCI without converting.

[Mild cognitive impairment: modern aspects of diagnostics and therapy]

The article provides a review of current literature on the diagnosis and treatment of mild cognitive impairment (MCI). MCI is not a common outcome of brain aging; it is an intermediate state between normal cognitive status and mild dementia. The MCI concept has been actively developing over the past few decades, a lot of knowledge and clinical experience has been accumulated, and numerous clinical trials are being conducted to develop effective methods of diagnosis and therapy. Treatment of pre-dementia cognitive disorders differs in many ways from therapy for dementia and has a better prognosis, therefore, it is recommended to diagnose and begin treating cognitive disorders as early as possible. The main possibilities of drug and non-drug therapy are described, with an emphasis on the use of the dopamine receptor agonist piribedil in the treatment of MCI and sensory deficit in elderly patients. The mechanisms of action of the drug are analyzed, data from the main clinical studies of the efficacy and safety of piribedil are presented: the positive effect of the drug on cognitive functions has been shown in more than 10 international clinical trials including about 7000 patients and in a number of post-marketing works performed on the Russian population of patients. Piribedil is successfully used for various types of cognitive disorders, both neurodegenerative and vascular, of mild to moderate severity.

Memory awareness disruptions in amnestic mild cognitive impairment: comparison of multiple awareness types for verbal and visuospatial material

Successful memory is normally accompanied by explicit awareness of retrieval and confidence in the accuracy of the retrieval product. Prior findings suggest that these features of metamemory can be dissociated from retrieval accuracy in Amnestic Mild Cognitive Impairment (aMCI). However, the literature on this question contains variable and conflicting results, likely because of differences in experimental conditions. We sought to systematically evaluate memory awareness disruptions in aMCI using multiple measures and stimulus formats within the same individuals. Memory awareness was tested with global predictions and postdictions, judgments of learning, confidence level ratings, and modified feeling-of-knowing ratings in tasks of visuospatial and verbal memory. These tests were administered to 14 individuals with aMCI and 15 healthy, age-matched controls. Memory awareness accuracy was calculated as the correspondence between subjective judgments and memory performance.Individuals with aMCI demonstrated impaired global and trial-level retrospective task awareness for visuospatial and verbal stimuli. Additionally, modified feeling-of-knowing awareness was impaired selectively for verbal stimuli. Statistical effect sizes for global awareness impairments were comparable to impairments in several objective neuropsychological memory assessments.Memory awareness (metamemory) disruptions in aMCI were most evident for a subset of subjective judgment types and task input modalities. These findings advance understanding of the nature of memory impairments in aMCI and support the utility of incorporating memory awareness testing to better characterize memory integrity in older adults.

An MRI-derived definition of MCI-to-AD conversion for long-term, automatic prognosis of MCI patients

Alzheimer's disease (AD) and mild cognitive impairment (MCI) are of great current research interest. While there is no consensus on whether MCIs actually “convert” to AD, this concept is widely applied. Thus, the more important question is not whether MCIs convert, but what is the best such definition. We focus on automatic prognostication, nominally using only a baseline brain image, of whether an MCI will convert within a multi-year period following the initial clinical visit. This is not a traditional supervised learning problem since, in ADNI, there are no definitive labeled conversion examples. It is not unsupervised, either, since there are (labeled) ADs and Controls, as well as cognitive scores for MCIs. Prior works have defined MCI subclasses based on whether or not clinical scores significantly change from baseline. There are concerns with these definitions, however, since, e.g., most MCIs (and ADs) do not change from a baseline CDR = 0.5 at any subsequent visit in ADNI, even while physiological changes may be occurring. These works ignore rich phenotypical information in an MCI patient's brain scan and labeled AD and Control examples, in defining conversion. We propose an innovative definition, wherein an MCI is a converter if any of the patient's brain scans are classified “AD” by a Control-AD classifier. This definition bootstraps design of a second classifier, specifically trained to predict whether or not MCIs will convert. We thus predict whether an AD-Control classifier will predict that a patient has AD. Our results demonstrate that this definition leads not only to much higher prognostic accuracy than by-CDR conversion, but also to subpopulations more consistent with known AD biomarkers (including CSF markers). We also identify key prognostic brain region biomarkers.