Do MCI criteria in drug trials accurately identify subjects with predementia Alzheimer's disease?

Effects of Transcranial Direct Current Stimulation on Cognitive Function in Older Adults with and without Mild Cognitive Impairment: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

INTRODUCTION

Noninvasive brain stimulation (NIBS) has shown benefits for cognitive function in older adults. However, the effects of transcranial direct current stimulation (tDCS) on cognitive function in older adults are inconsistent across studies, and the evidence for tDCS has limitations. We aim to explore whether tDCS can improve cognitive function and different cognitive domains (i.e., learning and memory and executive function) in adults aged 65 years and older with and without mild cognitive impairment and to further analyze the influencing factors of tDCS.

METHODS

Five English databases (PubMed, Cochrane Library, EMBASE, Web of Science, the cumulative Index to Nursing and Allied Health Literature [CINAHL]) and four Chinese databases were searched from inception to October 14, 2023. Literature screening, data extraction, and quality assessment were completed independently by two reviewers. All statistical analyses were conducted using RevMan software (version 5.3). Standardized mean difference (SMD) along with a 95% confidence interval (CI) was used to express the effect size of the outcomes, and a random-effect model was also used.

RESULTS

A total of 10 RCTs and 1,761 participants were included in the meta-analysis, and the risk of bias in those studies was relatively low. A significant effect favoring tDCS on immediate postintervention cognitive function (SMD = 0.16, Z = 2.36, p = 0.02) was found. However, the effects on immediate postintervention learning and memory (SMD = 0.20, Z = 2.00, p = 0.05) and executive function (SMD = 0.10, Z = 1.22, p = 0.22), and 1-month postintervention cognitive function (SMD = 0.12, Z = 1.50, p = 0.13), learning and memory (SMD = 0.17, Z = 1.39, p = 0.16), and executive function (SMD = 0.08, Z = 0.67, p = 0.51) were not statistically significant.

CONCLUSION

tDCS can significantly improve the immediate postintervention cognitive function of healthy older adults and MCI elderly individuals. Additional longitudinal extensive sample studies are required to clarify the specific effects of tDCS on different cognitive domains, and the optimal tDCS parameters need to be explored to guide clinical practice.

Feasibility of common, enjoyable game play for assessing daily cognitive functioning in older adults

Background

Frequent digital monitoring of cognition is a promising approach for assessing endpoints in prevention and treatment trials of Alzheimer's disease and related dementias (ADRD). This study evaluated the feasibility of the MIND GamePack© for recurrent semi-passive assessment of cognition across a longitudinal interval.

Methods

The MIND GamePack consists of four iPad-based games selected to be both familiar and enjoyable: Word Scramble, Block Drop, FreeCell, and Memory Match. Participants were asked to play 20 min/day for 5 days (100 min) for 4 months. Feasibility of use by older adults was assessed by measuring gameplay time and game performance. We also evaluated compliance through semi-structured surveys. A linear generalized estimating equation (GEE) model was used to analyze changes in gameplay time, and a regression tree model was employed to estimate the days it took for game performance to plateau. Subjective and environmental factors associated with gameplay time and performance were examined, including daily self-reported questions of memory and thinking ability, mood, sleep, energy, current location, and distractions prior to gameplay.

Results

Twenty-six cognitively-unimpaired older adults participated (mean age ± SD = 71.9 ± 8.6; 73% female). Gameplay time remained stable throughout the 4-months, with an average compliance rate of 91% ± 11% (1946 days of data across all participants) and weekly average playtime of 210 ± 132 min per participant. We observed an initial learning curve of improving game performance which on average, plateaued after 22-39 days, depending on the game. Higher levels of self-reported memory and thinking ability were associated with more gameplay time and sessions.

Conclusion

MIND GamePack is a feasible and well-designed semi-passive cognitive assessment platform which may provide complementary data to traditional neuropsychological testing in research on aging and dementia.

A graph theoretic approach to neurodegeneration: five data-driven neuropsychological subtypes in mild cognitive impairment

Mild cognitive Impairment (MCI) is notoriously heterogenous in terms of clinical presentation, neuroimaging correlates, and subsequent progression. Predicting who will progress to dementia, which type of dementia, and over what timeframe is challenging. Previous work has attempted to identify MCI subtypes using neuropsychological measures in an effort to address this challenge; however, there is no consensus on approach, which may account for some of the variability. Using a hierarchical community detection approach, we examined cognitive subtypes within an MCI sample (from the Alzheimer's Disease Neuroimaging Initiative [ADNI] study). We then examined whether these subtypes were related to biomarkers (e.g., cortical volumes, fluorodeoxyglucose (FDG)-positron emission tomography (PET) hypometabolism) or clinical progression. We identified five communities (i.e., cognitive subtypes) within the MCI sample: 1) predominantly memory impairment, 2) predominantly language impairment, 3) cognitively normal, 4) multidomain, with notable executive dysfunction, 5) multidomain, with notable processing speed impairment. Community membership was significantly associated with 1) cortical volume in the hippocampus, entorhinal cortex, and fusiform cortex; 2) FDG PET hypometabolism in the posterior cingulate, angular gyrus, and inferior/middle temporal gyrus; and 3) conversion to dementia at follow up. Overall, community detection as an approach appears a viable method for identifying unique cognitive subtypes in a neurodegenerative sample that were linked to several meaningful biomarkers and modestly with progression at one year follow up.

Metamodulation of presynaptic NMDA receptors: New perspectives for pharmacological interventions

Metamodulation shifted the scenario of the central neuromodulation from a simplified unimodal model to a multimodal one. It involves different receptors/membrane proteins physically associated or merely colocalized that act in concert to control the neuronal functions influencing each other. Defects or maladaptation of metamodulation would subserve neuropsychiatric disorders or even synaptic adaptations relevant to drug dependence. Therefore, this "vulnerability" represents a main issue to be deeply analyzed to predict its aetiopathogenesis, but also to propose targeted pharmaceutical interventions. The review focusses on presynaptic release-regulating NMDA receptors and on some of the mechanisms of their metamodulation described in the literature. Attention is paid to the interactors, including both ionotropic and metabotropic receptors, transporters and intracellular proteins, which metamodulate their responsiveness in physiological conditions but also undergo adaptation that are relevant to neurological dysfunctions. All these structures are attracting more and more the interest as promising druggable targets for the treatment of NMDAR-related central diseases: these substances would not exert on-off control of the colocalized NMDA receptors (as usually observed with NMDAR full agonists/antagonists), but rather modulate their functions, with the promise of limiting side effects that would favor their translation from preclinic to clinic.

Psychological treatments for depression and anxiety in dementia and mild cognitive impairment

BACKGROUND

Experiencing anxiety and depression is very common in people living with dementia and mild cognitive impairment (MCI). There is uncertainty about the best treatment approach. Drug treatments may be ineffective and associated with adverse effects. Guidelines recommend psychological treatments. In this updated systematic review, we investigated the effectiveness of different psychological treatment approaches.

OBJECTIVES

Primary objective To assess the clinical effectiveness of psychological interventions in reducing depression and anxiety in people with dementia or MCI. Secondary objectives To determine whether psychological interventions improve individuals' quality of life, cognition, activities of daily living (ADL), and reduce behavioural and psychological symptoms of dementia, and whether they improve caregiver quality of life or reduce caregiver burden.

SEARCH METHODS

We searched ALOIS, the Cochrane Dementia and Cognitive Improvement Group's register, MEDLINE, Embase, four other databases, and three trials registers on 18 February 2021.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) that compared a psychological intervention for depression or anxiety with treatment as usual (TAU) or another control intervention in people with dementia or MCI.

DATA COLLECTION AND ANALYSIS

A minimum of two authors worked independently to select trials, extract data, and assess studies for risk of bias. We classified the included psychological interventions as cognitive behavioural therapies (cognitive behavioural therapy (CBT), behavioural activation (BA), problem-solving therapy (PST)); 'third-wave' therapies (such as mindfulness-based cognitive therapy (MBCT)); supportive and counselling therapies; and interpersonal therapies. We compared each class of intervention with control. We expressed treatment effects as standardised mean differences or risk ratios. Where possible, we pooled data using a fixed-effects model. We used GRADE methods to assess the certainty of the evidence behind each result.

MAIN RESULTS

We included 29 studies with 2599 participants. They were all published between 1997 and 2020. There were 15 trials of cognitive behavioural therapies (4 CBT, 8 BA, 3 PST), 11 trials of supportive and counselling therapies, three trials of MBCT, and one of interpersonal therapy. The comparison groups received either usual care, attention-control education, or enhanced usual care incorporating an active control condition that was not a specific psychological treatment. There were 24 trials of people with a diagnosis of dementia, and five trials of people with MCI. Most studies were conducted in community settings. We considered none of the studies to be at low risk of bias in all domains.  Cognitive behavioural therapies (CBT, BA, PST) Cognitive behavioural therapies are probably slightly better than treatment as usual or active control conditions for reducing depressive symptoms (standardised mean difference (SMD) -0.23, 95% CI -0.37 to -0.10; 13 trials, 893 participants; moderate-certainty evidence). They may also increase rates of depression remission at the end of treatment (risk ratio (RR) 1.84, 95% CI 1.18 to 2.88; 2 studies, with one study contributing 2 independent comparisons, 146 participants; low-certainty evidence). We were very uncertain about the effect of cognitive behavioural therapies on anxiety at the end of treatment (SMD -0.03, 95% CI -0.36 to 0.30; 3 trials, 143 participants; very low-certainty evidence). Cognitive behavioural therapies probably improve patient quality of life (SMD 0.31, 95% CI 0.13 to 0.50; 7 trials, 459 participants; moderate-certainty evidence) and activities of daily living at end of treatment compared to treatment as usual or active control (SMD -0.25, 95% CI -0.40 to -0.09; 7 trials, 680 participants; moderate-certainty evidence). Supportive and counselling interventions Meta-analysis showed that supportive and counselling interventions may have little or no effect on depressive symptoms in people with dementia compared to usual care at end of treatment (SMD -0.05, 95% CI -0.18 to 0.07; 9 trials, 994 participants; low-certainty evidence). We were very uncertain about the effects of these treatments on anxiety, which was assessed only in one small pilot study. Other interventions There were very few data and very low-certainty evidence on MBCT and interpersonal therapy, so we were unable to draw any conclusions about the effectiveness of these interventions.

AUTHORS' CONCLUSIONS

CBT-based treatments added to usual care probably slightly reduce symptoms of depression for people with dementia and MCI and may increase rates of remission of depression. There may be important effect modifiers (degree of baseline depression, cognitive diagnosis, or content of the intervention). CBT-based treatments probably also have a small positive effect on quality of life and activities of daily living. Supportive and counselling interventions may not improve symptoms of depression in people with dementia. Effects of both types of treatment on anxiety symptoms are very uncertain. We are also uncertain about the effects of other types of psychological treatments, and about persistence of effects over time. To inform clinical guidelines, future studies should assess detailed components of these interventions and their implementation in different patient populations and in different settings.

Using historical data to facilitate clinical prevention trials in Alzheimer disease? An analysis of longitudinal MCI (mild cognitive impairment) data sets

BACKGROUND

The Placebo Group Simulation Approach (PGSA) aims at partially replacing randomized placebo-controlled trials (RPCTs), making use of data from historical control groups in order to decrease the needed number of study participants exposed to lengthy placebo treatment. PGSA algorithms to create virtual control groups were originally derived from mild cognitive impairment (MCI) data of the Alzheimer's Disease Neuroimaging Initiative (ADNI) database. To produce more generalizable algorithms, we aimed to compile five different MCI databases in a heuristic manner to create a "standard control algorithm" for use in future clinical trials.

METHODS

We compared data from two North American cohort studies (n=395 and 4328, respectively), one company-sponsored international clinical drug trial (n=831) and two convenience patient samples, one from Germany (n=726), and one from Switzerland (n=1558).

RESULTS

Despite differences between the five MCI samples regarding inclusion and exclusion criteria, their baseline demographic and cognitive performance data varied less than expected. However, the five samples differed markedly with regard to their subsequent cognitive performance and clinical development: (1) MCI patients from the drug trial did not deteriorate on verbal fluency over 3 years, whereas patients in the other samples did; (2) relatively few patients from the drug trial progressed from MCI to dementia (about 10% after 4 years), in contrast to the other four samples with progression rates over 30%.

CONCLUSION

Conventional MCI criteria were insufficient to allow for the creation of well-defined and internationally comparable samples of MCI patients. More recently published criteria for MCI or "MCI due to AD" are unlikely to remedy this situation. The Alzheimer scientific community needs to agree on a standard set of neuropsychological tests including appropriate selection criteria to make MCI a scientifically more useful concept. Patient data from different sources would then be comparable, and the scientific merits of algorithm-based study designs such as the PGSA could be properly assessed.

Polygenic Risk Score Analysis of Alzheimer's Disease in Cases without APOE4 or APOE2 Alleles

The We and others have previously shown that polygenic risk score analysis (PRS) has considerable predictive utility for identifying those at high risk of developing Alzheimer’s disease (AD) with an area under the curve (AUC) of >0.8. However, by far the greatest determinant of this risk is the apolipoprotein E locus with the E4 allele alone giving an AUC of ∼0.68 and the inclusion of the protective E2 allele increasing this to ∼0.69 in a clinical cohort. An important question is to determine how good PRS is at predicting risk in those who do not carry the E4 allele (E3 homozygotes, E3E2 and E2E2) and in those who carry neither the E4 or E2 allele (i.e. E3 homozygotes). Previous studies have shown that PRS remains a significant predictor of AD risk in clinical cohorts after controlling for APOE ε4 carrier status. In this study we assess the accuracy of PRS prediction in a cohort of pathologically confirmed AD cases and controls. The exclusion of APOE4 carriers has surprisingly little effect on the PRS prediction accuracy (AUC ∼0.83 [95% CI: 0.80-0.86]), and the accuracy remained higher than that in clinical cohorts with APOE included as a predictor. From a practical perspective this suggests that PRS analysis will have predictive utility even in E4 negative individuals and may be useful in clinical trial design.

A highly predictive signature of cognition and brain atrophy for progression to Alzheimer's dementia

BACKGROUND

Clinical trials in Alzheimer's disease need to enroll patients whose cognition will decline over time, if left untreated, in order to demonstrate the efficacy of an intervention. Machine learning models used to screen for patients at risk of progression to dementia should therefore favor specificity (detecting only progressors) over sensitivity (detecting all progressors), especially when the prevalence of progressors is low. Here, we explore whether such high-risk patients can be identified using cognitive assessments and structural neuroimaging by training machine learning tools in a high-specificity regime.

RESULTS

A multimodal signature of Alzheimer's dementia was first extracted from the ADNI1 dataset. We then validated the predictive value of this signature on ADNI1 patients with mild cognitive impairment (N = 235). The signature was optimized to predict progression to dementia over 3 years with low sensitivity (55.1%) but high specificity (95.6%), resulting in only moderate accuracy (69.3%) but high positive predictive value (80.4%, adjusted for a "typical" 33% prevalence rate of true progressors). These results were replicated in ADNI2 (N = 235), with 87.8% adjusted positive predictive value (96.7% specificity, 47.3% sensitivity, 85.1% accuracy).

CONCLUSIONS

We found that cognitive measures alone could identify high-risk individuals, with structural measurements providing a slight improvement. The signature had comparable receiver operating characteristics to standard machine learning tools, yet a marked improvement in positive predictive value was achieved over the literature by selecting a high-specificity operating point. The multimodal signature can be readily applied for the enrichment of clinical trials.

Better prognostic accuracy in younger mild cognitive impairment patients with more years of education

Introduction

Age and years of education influence the risk of dementia and may impact the prognostic accuracy of mild cognitive impairment subtypes.

Methods

Memory clinic patients without dementia (N = 358, age 64.0 ± 7.9) were stratified into four groups based on years of age (≤64 and ≥65) and education (≤12 and ≥13), examined with a neuropsychological test battery at baseline and followed up after 2 years.

Results

The prognostic accuracy of amnestic multi-domain mild cognitive impairment for dementia was highest in younger patients with more years of education and lowest in older patients with fewer years of education. Conversely, conversion rates to dementia were lowest in younger patients with more years of education and highest in older patients with fewer years of education.

Discussion

Mild cognitive impairment subtypes and demographic information should be combined to increase the accuracy of prognoses for dementia.

Alzheimer's disease diagnosis based on the Hippocampal Unified Multi-Atlas Network (HUMAN) algorithm

BACKGROUND

Hippocampal atrophy is a supportive feature for the diagnosis of probable Alzheimer's disease (AD). However, even for an expert neuroradiologist, tracing the hippocampus and measuring its volume is a time consuming and extremely challenging task. Accordingly, the development of reliable fully-automated segmentation algorithms is of paramount importance.

MATERIALS AND METHODS

The present study evaluates (i) the precision and the robustness of the novel Hippocampal Unified Multi-Atlas Network (HUMAN) segmentation algorithm and (ii) its clinical reliability for AD diagnosis. For these purposes, we used a mixed cohort of 456 subjects and their T1 weighted magnetic resonance imaging (MRI) brain scans. The cohort included 145 controls (CTRL), 217 mild cognitive impairment (MCI) subjects and 94 AD patients from Alzheimer's Disease Neuroimaging Initiative (ADNI). For each subject the baseline, repeat, 12 and 24 month follow-up scans were available.

RESULTS

HUMAN provides hippocampal volumes with a 3% precision; volume measurements effectively reveal AD, with an area under the curve (AUC) AUC₁ = 0.08 ± 0.02. Segmented volumes can also reveal the subtler effects present in MCI subjects, AUC₂ = 0.76 ± 0.05. The algorithm is stable and reproducible over time, even for 24 month follow-up scans.

CONCLUSIONS

The experimental results demonstrate HUMAN is a precise segmentation algorithm, besides hippocampal volumes, provided by HUMAN, can effectively support the diagnosis of Alzheimer's disease and become a useful tool for other neuroimaging applications.

Evaluation and clinical correlation of practical cut-offs for visual rating scales of atrophy: normal aging versus mild cognitive impairment and Alzheimer's disease

Age-related brain atrophy is a common finding, but neurodegenerative diseases such as Alzheimer's disease are associated with accelerated atrophy of the medial temporal lobe. In current practice for brain atrophy evaluation, several rating scales are being used such as the medial temporal atrophy (MTA), global cortical atrophy-frontal subscale (GCA-F) and posterior atrophy (PA) scales. Practical cut-offs to differentiate between normal and advanced brain atrophy are needed, because of their possible usefulness as a biomarker. A retrospective study was performed over a 1-year period resulting in a total of 79 subjects [27 patients with Alzheimer's disease (AD), 27 patients with minimal cognitive impairment (MCI) and 25 control subjects]. The MTA, GCA-F and PA scales were applied blinded and independent by two raters. Possible age- and disease-related cut-offs were computed. The MTA scale showed significantly better diagnostic performances and inter-rater agreement than the PA and GCA-F scales. We could not confirm the suggested MTA cut-off for each decade. However, an MTA score of >1 and >1.75 was considered pathological, respectively, in the population under and over 70 years. MTA can be of use in making distinction between age-related atrophy and abnormal increase of atrophy. Systematic assessment of regional brain atrophy through the use of MTA in MRI images could be a useful biomarker in aiding the early diagnosis of Alzheimer's disease.

Psychological Treatments for Depression and Anxiety in Dementia and Mild Cognitive Impairment

The Mission of the Cochrane Nursing Care Field (CNCF) is to improve health outcomes through increasing the use of the Cochrane Library and supporting Cochrane's role by providing an evidence base for nurses and related healthcare professionals involved in delivering, leading, or researching nursing care. The CNCF produces "Cochrane Corner" columns (summaries of recent nursing-care-relevant Cochrane Reviews) that are regularly published in collaborating nursing-care-related journals. Information on the processes this Field has developed can be accessed at: http://cncf.cochrane.org/evidence-transfer-program-review-summaries.

Psychological treatments for depression and anxiety in dementia and mild cognitive impairment: systematic review and meta-analysis

BACKGROUND

Anxiety and depression are common in people with dementia and mild cognitive impairment (MCI), but there is uncertainty about the effectiveness of both pharmacological and psychological therapies.

AIMS

To evaluate the evidence of effectiveness of psychological treatments in treating depression and anxiety in people with dementia and MCI.

METHOD

We carried out a systematic review and meta-analysis of randomised controlled trials (RCTs) of psychological treatment versus usual care in people with dementia and MCI. Primary outcomes were symptoms of anxiety and depression. Secondary outcomes were quality of life, ability to perform daily activities, neuropsychiatric symptoms, cognition and caregivers' self-rated depressive symptoms.

RESULTS

We included six RCTs, involving 439 participants with dementia, which used cognitive-behavioural therapy, interpersonal therapy, counselling or multimodal interventions including a specific psychological therapy. We found beneficial effects for both depression and anxiety. Overall, the quality of the evidence was moderate for depression and low for anxiety, due to the methodological limitations of the studies we identified and the limited number of trials.

CONCLUSIONS

The evidence from six RCTs suggests that psychological treatments are effective in reducing symptoms of depression and anxiety for people with dementia. There is a need for high-quality, multicentre trials including standardised, well-defined interventions.

Boosting diagnosis accuracy of Alzheimer's disease using high dimensional recognition of longitudinal brain atrophy patterns

OBJECTIVE

Boosting accuracy in automatically discriminating patients with Alzheimer's disease (AD) and normal controls (NC), based on multidimensional classification of longitudinal whole brain atrophy rates and their intermediate counterparts in analyzing magnetic resonance images (MRI).

METHOD

Longitudinal percentage of brain volume changes (PBVC) in two-year follow up and its intermediate counterparts in early 6-month and late 18-month are used as features in supervised and unsupervised classification procedures based on K-mean, fuzzy clustering method (FCM) and support vector machine (SVM). The most relevant features for classification are selected using discriminative analysis (DA) of features and their principal components (PC). Accuracy of the proposed method is evaluated in a group of 30 patients with AD (16 males, 14 females, age±standard-deviation (SD)=75±1.36 years) and 30 normal controls (15 males, 15 females, age±SD=77±0.88 years) using leave-one-out cross-validation.

RESULTS

Results indicate superiority of supervised machine learning techniques over unsupervised ones in diagnosing AD and withal, predominance of RBF kernel over lineal one. Accuracies of 83.3%, 83.3%, 90% and 91.7% are achieved in classification by K-mean, FCM, linear SVM and SVM with radial based function (RBF) respectively.

CONCLUSION

Evidence that SVM classification of longitudinal atrophy rates may results in high accuracy is given. Additionally, it is realized that use of intermediate atrophy rates and their principal components improves diagnostic accuracy.

Is Mild Cognitive Impairment a Valid Target of Therapy

The status of Mild Cognitive Impairment (MCI) as a valid construct is controversial. The term encompasses people with heterogeneous clinical profiles, and invites sub-classifications that still require validation. Still, much evidence suggests that, properly selected, many people with MCI - especially Amnestic MCI - are at a high risk of dementia. This paper considers the validity of the construct of MCI as a high-risk state for progression and a target for treatment. We conclude that the status of MCI as an entity remains controversial. On the one hand, it can be argued that the careful section of cases at high risk of developing dementia means that it is a valid target, with the goal being the prevention of dementia. Advocates of this view see a linear progression that they are trying to arrest, but studies have yet to show that this can be done. On the other hand, it can be argued that the patients who progressed did not develop dementia: they actually had a very early form of it. By this view, people without the progressive form will be needlessly exposed to antidementia drugs, and the others should be treated anyway. Why some people progress and others do not is not clear, but the variable rates of progression - between clinic-based and population-based samples and between very similar clinical trials with slightly different inclusion criteria - suggests that MCI is a heterogeneous entity. The phenomenon of slowing or non-progression itself should be investigated, and such investigations likely should extend to people now classified as having mild dementia.

Mild cognitive impairment. Part 2: Biological markers for diagnosis and prediction of dementia in Alzheimer's disease

OBJECTIVE

To present a critical review of publications reporting on the rationale and clinical implications of the use of biomarkers for the early diagnosis of Alzheimer's disease (AD).

METHODS

We conducted a systematic search of the PubMed and Web of Science electronic databases, limited to articles published in English between 1999 and 2012, and based on the following terms: mild cognitive impairment, Alzheimer's disease OR dementia, biomarkers. We retrieved 1,130 articles, of which 175 were reviews. Overall, 955 original articles were eligible.

RESULTS

The following points were considered relevant for the present review: a) rationale for biomarkers research in AD and mild cognitive impairment (MCI); b) usefulness of distinct biomarkers for the diagnosis and prediction of AD; c) the role of multimodality biomarkers for the diagnosis and prediction of AD; d) the role of biomarkers in clinical trials of patients with AD and MCI; and e) current limitations to the widespread use of biomarkers in research and clinical settings.

CONCLUSION

Different biomarkers are useful for the early diagnosis and prediction of AD in at-risk subjects. Nonetheless, important methodological limitations need to be overcome for widespread use of biomarkers in research and clinical settings.

Psychological treatments for depression and anxiety in dementia and mild cognitive impairment

BACKGROUND

Experiencing anxiety and depression is very common in people with dementia and mild cognitive impairment (MCI). Psychological interventions have been suggested as a potential treatment for these populations. Current research suggests that people with dementia and MCI have limited opportunities for psychological treatments aimed at improving their well-being. A systematic review of the evidence on their effectiveness is likely to be useful in terms of improving outcomes for patients and for future recommendations for practice.

OBJECTIVES

The main objective of this review was to assess the effectiveness of psychological interventions in reducing anxiety and depression in people with dementia or mild cognitive impairment (MCI).

SEARCH METHODS

We searched the Cochrane Dementia and Cognitive Improvement Group Specialized Register and additional sources for both published and unpublished data.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) comparing a psychological intervention with usual care or a placebo intervention (social contact control) in people with dementia or MCI.

DATA COLLECTION AND ANALYSIS

Two review authors worked independently to select trials, extract data and assess studies for risk of bias, using a data extraction form. We contacted authors when further information was not available from the published articles.

MAIN RESULTS

Six RCTs involving 439 participants with dementia were included in the review, but no studies of participants with MCI were identified. The studies included people with dementia living in the community or in nursing home care and were carried out in several countries. Only one of the studies was classified as low risk of bias. Five studies were at unclear or high risk of bias due to uncertainties around randomisation, blinding and selective reporting of results. The studies used the different psychological approaches of cognitive behavioural therapy (CBT), interpersonal therapy and counselling. Two studies were of multimodal interventions including a specific psychological therapy. The comparison groups received either usual care, attention-control educational programs, diagnostic feedback or services slightly above usual care.Meta-analysis showed a positive effect of psychological treatments on depression (6 trials, 439 participants, standardised mean difference (SMD) -0.22; 95% confidence interval (CI) -0.41 to -0.03, moderate quality evidence) and on clinician-rated anxiety (2 trials, 65 participants, mean difference (MD) -4.57; 95% CI -7.81 to -1.32, low quality evidence), but not on self-rated anxiety (2 trials, SMD 0.05; 95% CI -0.44 to 0.54) or carer-rated anxiety (1 trial, MD -2.40; 95% CI -4.96 to 0.16). Results were compatible with both benefit and harm on the secondary outcomes of patient quality of life, activities of daily living (ADLs), neuropsychiatric symptoms and cognition, or on carers' self-rated depressive symptoms, but most of the studies did not measure these outcomes. There were no reports of adverse events.

AUTHORS' CONCLUSIONS

We found evidence that psychological interventions added to usual care can reduce symptoms of depression and clinician-rated anxiety for people with dementia. We conclude that psychological interventions have the potential to improve patient well-being. Further high quality studies are needed to investigate which treatments are most effective and to evaluate the effect of psychological interventions in people with MCI.

The presence of behavioural and psychological symptoms and progression to dementia in the cognitively impaired older population

OBJECTIVE

Behavioural and psychological symptoms (BPS) are common in the older population and may be an indication of early dementia. We explored the predictive effect of the presence of BPS on the 2-year progression to dementia in a cognitively impaired population aged 65 years and over without dementia at baseline.

METHODS

Twelve symptoms were measured in 2024 participants without dementia at baseline as part of a population-based longitudinal study of ageing. The risk of progression to dementia was predicted in those with cognitive impairment for each individual BPS and using a BPS composite score.

RESULTS

Wandering and persecution were independently associated with progression to dementia after adjustment for socio-demographic factors, cognitive domains and other BPS. When stratifying by cognitive function, those with low cognition (MMSE 0-18) and 4 or more BPS were more likely to progress to dementia than those without BPS.

CONCLUSIONS

We have shown that some psychiatric symptoms are associated with increased short-term progression to dementia in those with low cognition. The predictive effect of BPS in dementia progression has implications for risk stratification of those at high risk of progression to dementia, along with memory impairment, other cognitive impairment and health variables.

Multilocus genetic profiling to empower drug trials and predict brain atrophy

Designers of clinical trials for Alzheimer's disease (AD) and mild cognitive impairment (MCI) are actively considering structural and functional neuroimaging, cerebrospinal fluid and genetic biomarkers to reduce the sample sizes needed to detect therapeutic effects. Genetic pre-selection, however, has been limited to Apolipoprotein E (ApoE). Recently discovered polymorphisms in the CLU, CR1 and PICALM genes are also moderate risk factors for AD; each affects lifetime AD risk by ~ 10–20%. Here, we tested the hypothesis that pre-selecting subjects based on these variants along with ApoE genotype would further boost clinical trial power, relative to considering ApoE alone, using an MRI-derived 2-year atrophy rate as our outcome measure. We ranked subjects from the Alzheimer's Disease Neuroimaging Initiative (ADNI) based on their cumulative risk from these four genes. We obtained sample size estimates in cohorts enriched in subjects with greater aggregate genetic risk. Enriching for additional genetic biomarkers reduced the required sample sizes by up to 50%, for MCI trials. Thus, AD drug trial enrichment with multiple genotypes may have potential implications for the timeliness, cost, and power of trials.

•

ApoE genotype status helps enrich MCI trials, using a structural MRI outcome measure.

•

CLU, PICALM and CR1 risk genes boost potential MCI trial power beyond ApoE alone.

•

CLU, PICALM and CR1 show significant, aggregate effects on TBM maps of brain atrophy.

Clinical trials in predementia stages of Alzheimer disease

Effective treatments of Alzheimer disease (AD) dementia are an urgent necessity. There is a growing consensus that effective disease-modifying treatment before the onset of clinical dementia and slowing the progression of mild symptoms are needed after recent setbacks in AD therapeutics. The identification of at-risk and preclinical AD populations is becoming important for targeting primary and secondary prevention clinical trials in AD. This article reviews the strategies and challenges in targeting at-risk and preclinical AD populations for a new generation of AD clinical trials. Design, outcome measures, and complexities in successfully completing a clinical trial targeting this population are reviewed.

Huperzine A for mild cognitive impairment

BACKGROUND

Mild cognitive impairment (MCI) has been proposed as a condition of intermediate symptomatology between the cognitive changes of ageing and fully developed symptoms of dementia. Treatment in the stages of MCI may delay the deterioration of cognitive impairment and delay the progression to dementia. Currently, the treatments for Alzheimer's disease have been focused on increasing acetylcholine levels in the brain. However, these drugs have not been proven to be effective for MCI and have numerous side effects. Huperzine A may have some beneficial effects in MCI.

OBJECTIVES

To assess the clinical efficacy and safety of huperzine A for the treatment of patients with MCI.

SEARCH METHODS

We searched ALOIS: the Cochrane Dementia and Cognitive Improvement Group's Specialized Register on 23 May 2011 using the terms: huperzine, ayapin, scoparon. ALOIS contains records of clinical trials identified from monthly searches of a number of major healthcare databases, numerous trial registries and grey literature sources. Additional searches were also performed separately in MEDLINE, EMBASE, PsycINFO, LILACS, clinicalTrials.gov, the ICTRP (WHO portal), CENTRAL (The Cochrane Library) and Web of Science with Conference Proceedings.The following Chinese databases were searched: The Chinese Biomedical Database, VIP Chinese Science and Technique Journals Database, China National Knowledge Infrastructure and The Chinese Clinical Trials Register. In addition, we handsearched 20 Chinese traditional medicine journals from between 1970 and 1989.

SELECTION CRITERIA

Randomised, parallel-group, placebo-controlled trials comparing huperzine A with placebo in patients with MCI were eligible for inclusion.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed studies for their eligibility for inclusion.

MAIN RESULTS

No eligible trials were identified. In the absence of any suitable randomised placebo-controlled trials in this area, we were unable to perform a meta-analysis.

AUTHORS' CONCLUSIONS

The currently available evidence is insufficient to assess the potential for huperzine A in the treatment of MCI. Randomised double-blind placebo-controlled trials are needed.

Fluid biomarkers in Alzheimer disease

Research progress has provided detailed understanding of the molecular pathogenesis of Alzheimer disease (AD). This knowledge has been translated into new drug candidates with putative disease-modifying effects, which are now being tested in clinical trials. The promise of effective therapy has created a great need for biomarkers able to detect AD in the predementia phase, because drugs will probably be effective only if neurodegeneration is not too advanced. In this chapter, cerebrospinal fluid (CSF) and plasma biomarkers are reviewed. The core CSF biomarkers total tau (T-tau), phosphorylated tau (P-tau) and the 42 amino acid form of β-amyloid (Aβ42) reflect AD pathology, and have high diagnostic accuracy to diagnose AD with dementia and prodromal AD in mild cognitive impairment cases. The rationale for the use of CSF biomarkers to identify and monitor the mechanism of action of new drug candidates is also outlined in this chapter.

Diagnostic and economic evaluation of new biomarkers for Alzheimer's disease: the research protocol of a prospective cohort study

Background

New research criteria for the diagnosis of Alzheimer’s disease (AD) have recently been developed to enable an early diagnosis of AD pathophysiology by relying on emerging biomarkers. To enable efficient allocation of health care resources, evidence is needed to support decision makers on the adoption of emerging biomarkers in clinical practice. The research goals are to 1) assess the diagnostic test accuracy of current clinical diagnostic work-up and emerging biomarkers in MRI, PET and CSF, 2) perform a cost-consequence analysis and 3) assess long-term cost-effectiveness by an economic model.

Methods/design

In a cohort design 241 consecutive patients suspected of having a primary neurodegenerative disease are approached in four academic memory clinics and followed for two years. Clinical data and data on quality of life, costs and emerging biomarkers are gathered.

Diagnostic test accuracy is determined by relating the clinical practice and new research criteria diagnoses to a reference diagnosis. The clinical practice diagnosis at baseline is reflected by a consensus procedure among experts using clinical information only (no biomarkers). The diagnosis based on the new research criteria is reflected by decision rules that combine clinical and biomarker information. The reference diagnosis is determined by a consensus procedure among experts based on clinical information on the course of symptoms over a two-year time period.

A decision analytic model is built combining available evidence from different resources among which (accuracy) results from the study, literature and expert opinion to assess long-term cost-effectiveness of the emerging biomarkers.

Discussion

Several other multi-centre trials study the relative value of new biomarkers for early evaluation of AD and related disorders. The uniqueness of this study is the assessment of resource utilization and quality of life to enable an economic evaluation. The study results are generalizable to a population of patients who are referred to a memory clinic due to their memory problems.

Trial registration

NCT01450891

Development of a small D-enantiomeric Alzheimer's amyloid-β binding peptide ligand for future in vivo imaging applications

Alzheimer’s disease (AD) is a devastating disease affecting predominantly the aging population. One of the characteristic pathological hallmarks of AD are neuritic plaques, consisting of amyloid-β peptide (Aβ). While there has been some advancement in diagnostic classification of AD patients according to their clinical severity, no fully reliable method for pre-symptomatic diagnosis of AD is available. To enable such early diagnosis, which will allow the initiation of treatments early in the disease progress, neuroimaging tools are under development, making use of Aβ-binding ligands that can visualize amyloid plaques in the living brain. Here we investigate the properties of a newly designed series of D-enantiomeric peptides which are derivatives of ACI-80, formerly called D1, which was developed to specifically bind aggregated Aβ1–42. We describe ACI-80 derivatives with increased stability and Aβ binding properties, which were characterized using surface plasmon resonance and enzyme-linked immunosorbent assays. The specific interactions of the lead compounds with amyloid plaques were validated by ex vivo immunochemistry in transgenic mouse models of AD. The novel compounds showed increased binding affinity and are promising candidates for further development into in vivo imaging compounds.

The prognostic value of amyloid imaging

Mild cognitive impairment is characterized by a decline in cognitive performance without interference with activities of daily living. The amnestic subtype of mild cognitive impairment progresses to Alzheimer's disease at a rate of 10-15% per year and in the majority the neuropathology is intermediate between the neuropathological changes of typical ageing and Alzheimer's disease. Amyloid deposition occurs over a decade before the development of noticeable cognitive symptoms in a continuous process that starts in healthy elderly individuals. Newly developed PET amyloid imaging agents provide noninvasive biomarkers for the early in vivo detection of Alzheimer's pathology in healthy elderly individuals and those with mild cognitive impairment. Exclusion of amyloid pathology should allow a more accurate prognosis to be given and ensure appropriate recruitment into clinical trials testing the efficacy of new putative antiamyloid agents at an earlier disease stage. The development of (18)F-labelled amyloid imaging agents has increased the availability of this new technology for clinical and research use since they can be used in PET centres where a cyclotron and radiochemistry are not available. This review discusses the role of PET imaging for assessing the amyloid load in cognitively normal elderly subjects and subjects with mild cognitive impairment at risk of conversion to Alzheimer's disease.

Aspirin, steroidal and non-steroidal anti-inflammatory drugs for the treatment of Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is the most common form of dementia. The incidence of AD rises exponentially with age and its prevalence will increase significantly worldwide in the next few decades. Inflammatory processes have been suspected in the pathogenesis of the disease.

OBJECTIVES

To review the efficacy and side effects of aspirin, steroidal and non-steroidal anti-inflammatory drugs (NSAIDs) in the treatment of AD, compared to placebo.

SEARCH METHODS

We searched ALOIS: the Cochrane Dementia and Cognitive Improvement Group's Specialized Register on 12 April 2011 using the terms: aspirin OR "cyclooxygenase 2 inhibitor" OR aceclofenac OR acemetacin OR betamethasone OR celecoxib OR cortisone OR deflazacort OR dexamethasone OR dexibruprofen OR dexketoprofen OR diclofenac sodium OR diflunisal OR diflusinal OR etodolac OR etoricoxib OR fenbufen OR fenoprofen OR flurbiprofen OR hydrocortisone OR ibuprofen OR indometacin OR indomethacin OR ketoprofen OR lumiracoxib OR mefenamic OR meloxicam OR methylprednisolone OR nabumetone OR naproxen OR nimesulide OR "anti-inflammatory" OR prednisone OR piroxicam OR sulindac OR tenoxicam OR tiaprofenic acid OR triamcinolone OR NSAIDS OR NSAID. ALOIS contains records of clinical trials identified from monthly searches of a number of major healthcare databases (including MEDLINE, EMBASE, PsycINFO, CINAHL, LILACS), numerous trial registries (including national, international and pharmacuetical registries) and grey literature sources.

SELECTION CRITERIA

All randomised controlled trials assessing the efficacy of aspirin, steroidal and non-steroidal anti-inflammatory drugs in AD.

DATA COLLECTION AND ANALYSIS

One author assessed risk of bias of each study and extracted data. A second author verified data selection.

MAIN RESULTS

Our search identified 604 potentially relevant studies. Of these, 14 studies (15 interventions) were RCTs and met our inclusion criteria. The numbers of participants were 352, 138 and 1745 for aspirin, steroid and NSAIDs groups, respectively. One selected study comprised two separate interventions. Interventions assessed in these studies were grouped into four categories: aspirin (three interventions), steroids (one intervention), traditional NSAIDs (six interventions), and selective cyclooxygenase-2 (COX-2) inhibitors (five interventions). All studies were evaluated for internal validity using a risk of bias assessment tool. The risk of bias was low for five studies, high for seven studies, and unclear for two studies.There was no significant improvement in cognitive decline for aspirin, steroid, traditional NSAIDs and selective COX-2 inhibitors. Compared to controls, patients receiving aspirin experienced more bleeding while patients receiving steroid experienced more hyperglycaemia, abnormal lab results and face edema. Patients receiving NSAIDs experienced nausea, vomiting, elevated creatinine, elevated LFT and hypertension. A trend towards higher death rates was observed among patients treated with NSAIDS compared with placebo and this was somewhat higher for selective COX-2 inhibitors than for traditional NSAIDs.

AUTHORS' CONCLUSIONS

Based on the studies carried out so far, the efficacy of aspirin, steroid and NSAIDs (traditional NSAIDs and COX-2 inhibitors) is not proven. Therefore, these drugs cannot be recommended for the treatment of AD.

Detection of Soluble Amyloid-β Oligomers and Insoluble High-Molecular-Weight Particles in CSF: Development of Methods with Potential for Diagnosis and Therapy Monitoring of Alzheimer's Disease

The diagnosis of probable Alzheimer's disease (AD) can be established premortem based on clinical criteria like neuropsychological tests. Post mortem, specific neuropathological changes like amyloid plaques define AD. However, the standard criteria based on medical history and mental status examinations do not take into account the long preclinical features of the disease, and a biomarker for improved diagnosis of AD is urgently needed. In a large number of studies, amyloid-β (Aβ) monomer concentrations in CSF of AD patients are consistently and significantly reduced when compared to healthy controls. Therefore, monomeric Aβ in CSF was suggested to be a helpful biomarker for the diagnosis of preclinical AD. However, not the monomeric form, but Aβ oligomers have been shown to be the toxic species in AD pathology, and their quantification and characterization could facilitate AD diagnosis and therapy monitoring. Here, we review the current status of assay development to reliably and routinely detect Aβ oligomers and high-molecular-weight particles in CSF.

Occurrence of medical co-morbidity in mild cognitive impairment: implications for generalisation of MCI research

BACKGROUND

diagnosis of mild cognitive impairment (MCI) typically excludes individuals with medical co-morbidity. Interest in MCI screening raises the questions of what are the best criteria to identify a representative sample and what factors are associated with MCI progression to dementia.

OBJECTIVES

to compare the pattern of disease co-morbidity across different cognitive groups and to examine the role of health co-morbidity as a risk factor for dementia progression from MCI.

METHODS

individuals from the MRC Cognitive Function and Ageing Study were classified as having no cognitive impairment (NCI), MCI, other cognitive impairment no dementia (OCIND) or dementia. At 2 years dementia status was assessed.

FINDINGS

over 50% of individuals in each group reported one or more medical condition. The pattern of disease prevalence was similar in the NCI, MCI and OCIND groups. Anaemia was the only health factor associated with an increased risk of dementia progression from MCI.

CONCLUSION

classification of MCI using medical exclusions would exclude the majority of the population from a MCI diagnosis. This has implications for treatment decisions and clinical trial recruitment. This could not only make recruitment more difficult but also limit the generalisability of trial results. Medical co-morbidity does not help to distinguish progressive from non-progressive MCI.

CSF biomarkers in neurodegenerative diseases

Neurodegenerative diseases are major world wide causes of morbidity and mortality. They form a heterogeneous group of diseases, ranging from rare monogenic inherited errors of metabolism to common multi-factorial dementias. Major research efforts focus on the development of disease modifying drugs for neurodegenerative diseases. As a result, there follows a need for reliable tools for diagnosis, prognosis and monitoring of therapy. Processes in the brain can be monitored by analysis of cerebrospinal fluid (CSF). Several CSF biomarkers of pathological processes in the brain are now available. Such biomarkers may be used for both research and in the clinical setting. However, several difficult problems remain to be solved. More intensive collaboration between academia, industry and government is likely needed to develop treatments and biomarkers for neurodegenerative diseases. This article reviews the definitions, usage and current limitations of CSF biomarkers in this field.

Diagnosis and biomarkers of predementia in Alzheimer's disease

In view of the growing prevalence of Alzheimer's disease (AD) worldwide, there is an urgent need for the development of better diagnostic tools and more effective therapeutic interventions. At the earliest stages of AD, no significant cognitive or functional impairment is detected by conventional clinical methods. However, new technologies based on structural and functional neuroimaging, and on the biochemical analysis of cerebrospinal fluid (CSF) may reveal correlates of intracerebral pathology in individuals with mild, predementia symptoms. These putative correlates are commonly referred to as AD-related biomarkers. The relevance of the early diagnosis of AD relies on the hypothesis that pharmacological interventions with disease-modifying compounds are likely to produce clinically relevant benefits if started early enough in the continuum towards dementia. Here we review the clinical characteristics of the prodromal and transitional states from normal cognitive ageing to dementia in AD. We further address recent developments in biomarker research to support the early diagnosis and prediction of dementia, and point out the challenges and perspectives for the translation of research data into clinical practice.

Optimizing mild cognitive impairment for discriminating dementia risk in the general older population

BACKGROUND

Criteria for mild cognitive impairment (MCI) predict dementia risk in the clinic. Dementia risk in the population is different and whether there is an optimal MCI-derived threshold for discriminating at-risk from not-at-risk cases in the general older population is not known.

METHODS

Data were from the Medical Research Council Cognitive Function and Ageing Study. Two risk thresholds were derived from each of seven different concepts of MCI including: Mayo Clinic-defined amnestic, nonamnestic, multiple, and revised MCI, MCI based on Mini-Mental State Examination derived categories, and the definitions of Cognitive Impairment No Dementia and Age-Related Cognitive Decline (ARCD). Receiver operating characteristic analysis was used to compare the predictive validity of 2-year incident dementia for each risk threshold across the different MCI definitions.

FINDINGS

MCI-derived risk thresholds varied in their ability to predict dementia. MCI thresholds were accurate in identifying individuals not at-risk of dementia progression (false-negative range: 0%–3.4%). No MCI-derived threshold accurately identified an at-risk group with a 2-year progression rate greater than 20%. Criteria for ARCD defined the threshold with the highest sensitivity and specificity for dementia conversion.

INTERPRETATION

MCI-derived thresholds do not reliably identify individuals at-risk of incident dementia at 2 years when applied in the general population. A large subpopulation of individuals not at-risk was more reliably identified. What is considered a sufficient level of accuracy for identification of individuals at increased risk of dementia depends on the motivation for screening and on the safety and efficacy of available interventions.

Affective symptoms as predictors of Alzheimer's disease in subjects with mild cognitive impairment: a 10-year follow-up study

BACKGROUND

Affective symptoms are common in subjects with mild cognitive impairment (MCI), but there is disagreement whether these symptoms are predictive for Alzheimer's disease (AD). We investigated the predictive accuracy of affective symptoms for AD during a follow-up study in subjects with MCI, and whether the predictive accuracy was modified by age, the presence of amnestic MCI or the length of follow-up.

METHOD

Newly referred subjects (n=263) with MCI older than 55 years were selected from a memory clinic and followed up after 2, 5 and 10 years. Predictors investigated were: symptoms of depression, anxiety, apathy and sleeping problems.

RESULTS

Affective symptoms were present in 50-70% of the subjects. The average follow-up period was 5.4 years and 79 subjects (29%) developed AD. Sleeping problems were associated with a decreased risk for AD [odds ratio (OR) 0.35, p<0.001]. Symptoms of depression (OR 0.61, p=0.059) and anxiety (OR 0.58, p=0.051) showed a trend in the same direction. The OR of apathy for AD was 0.67 (p=0.14). Depression was associated with a decreased risk for AD only in subjects without amnestic MCI, but not in subjects with amnestic MCI. Moreover, anxiety was related to the risk for AD differently between subjects diagnosed with AD at the 5-year follow-up (OR 0.23) and subjects diagnosed with AD at the 10-year follow-up (OR 1.7).

CONCLUSIONS

Affective symptoms are associated with a decreased risk for AD. The risk may be dependent on MCI subtype or length of follow-up, but it does not depend on age.

Enrichment through biomarkers in clinical trials of Alzheimer's drugs in patients with mild cognitive impairment

Clinical trials of disease modifying drugs for Alzheimer's disease (AD) in patients with mild cognitive impairment (MCI) might benefit from enrichment with true AD cases. Four hundred five MCI patients (143 converters and 262 nonconverters to AD within 2 years) of the Alzheimer's disease Neuroimaging Initiative (ADNI) were used. Markers for enrichment were hippocampal atrophy on magnetic resonance (MRI), temporoparietal hypometabolism on FDG PET, cerebrospinal fluid (CSF) biomarkers (Abeta42, tau, and phospho-tau), and cortical amyloid deposition (11C-PIB positron emission tomography (PET)). Two separate enrichment strategies were tested to A) maximize the proportion of MCI converters screened in, and B) minimize the proportion of MCI converters screened out. Based on strategy A, when compared with no enrichment and ADAS-Cog as an outcome measure (sample size of 834), enrichment with 18F-FDG PET and hippocampal volume lowered samples size to 260 and 277 cases per arm, but at the cost of screening out 1,597 and 434 cases per arm. When compared with no enrichment and clinical dementia rating (CDR-SOB) as an outcome measure (sample size of 674), enrichment with hippocampal volume and Abeta42 lowered sample sizes to 191 and 291 cases per arm, with 639 and 157 screened out cases. Strategy B reduced the number of screened out cases (740 for [11C]-PIB PET, 101 hippocampal volume, 82 ADAS-COG and 330 for [18F]-FDG PET) but at the expense of decreased power and a relative increase size (740 for [11C]-PIB PET, 676 for hippocampal volume, 744 for ADAS-Cog, and 517 for [18F]-FDG PET). Enrichment comes at the price of an often relevant proportion of screened out cases, and in clinical trial settings, the balance between enrichment of screened in and loss of screened out patients should be critically discussed.

Biochemical markers in Alzheimer's disease clinical trials

This article summarizes how biochemical markers may aid in the development of novel treatments that interfere with fundamental pathogenic processes in Alzheimer's disease. Details are given on the potential use of biomarkers in Alzheimer's disease clinical trials as additional inclusion criteria to enrich study populations with participants who really suffer from the disease, as a means to stratify study participants into meaningful subgroups that may benefit differently from the treatment, and as tools to detect desired biochemical effects and undesired side effects of the drug.

Exploring the recollective experience during autobiographical memory retrieval in amnestic mild cognitive impairment

Autonoetic consciousness refers to the ability to mentally transport oneself back in subjective time to relive elements of, or all, of a past event, and is compromised in the early stages of Alzheimer's disease (AD). Here, we investigate autobiographical memory (ABM) and the recollective experience in amnestic mild cognitive impairment (aMCI). aMCI participants exhibited significant deficits compared with healthy elderly controls for both personal semantic and event detail components of ABM. These decrements were evident across all life epochs for episodic recall. Recall of an event that occurred 1 week previously, was tested in the same spatiotemporal context, and provided the greatest group dissociation, with elderly controls benefitting from a context-dependent memory effect. This reinstantiation of context did not ameliorate the anterograde deficits in the aMCI cohort, nor did it facilitate the mental reliving of these memories for either participant group. Whereas reliving judgments were comparable in both groups, aMCI participants exhibited a compromised capacity to generate vivid, self-referential visual imagery and to re-experience the original emotion of events. These contextual and experiential deficits extended beyond recently encountered events into remote epochs, and suggest a greater level of ABM impairment in aMCI than previously assumed.

Clinical and biological predictors of Alzheimer's disease in patients with amnestic mild cognitive impairment

OBJECTIVE

To identify predictors of the progression from pre-dementia stages of cognitive impairment in Alzheimer's disease is relevant to clinical management and to substantiate the decision of prescribing antidementia drugs.

METHOD

Longitudinal study of a cohort of elderly adults with amnestic mild cognitive impairment and healthy controls, carried out to estimate the risk and characterize predictors of the progression to Alzheimer's disease.

RESULTS

Patients with amnestic mild cognitive impairment had a higher risk to develop Alzheimer's disease during follow-up (odds ratio = 4.5, CI₉₅(%) [1.3-13.6], p = 0.010). At baseline, older age, lower scores on memory tests and presence of the APOE*4 allele predicted the progression from amnestic mild cognitive impairment to Alzheimer's disease. In a sub sample of amnestic mild cognitive impairment patients, those who progressed to Alzheimer's disease had lower cerebrospinal fluid concentrations of amyloid-beta peptide (Aβ₄₂, p = 0.020) and higher concentrations of total TAU (p = 0.030) and phosphorylated TAU (p = 0.010), as compared to non-converters.

DISCUSSION

This is the first Brazilian study to report cerebrospinal fluid biomarkers in the prediction of the conversion from MCI to Alzheimer's disease. Our data are in accordance with those reported in other settings. The measurement of cerebrospinal fluid total-TAU, phospho-TAU and Aβ₄₂ may help identify patients with mild cognitive impairment at higher risk for developing Alzheimer's disease.

Cerebrospinal fluid and plasma biomarkers in Alzheimer disease

Intense multidisciplinary research has provided detailed knowledge of the molecular pathogenesis of Alzheimer disease (AD). This knowledge has been translated into new therapeutic strategies with putative disease-modifying effects. Several of the most promising approaches, such as amyloid-beta immunotherapy and secretase inhibition, are now being tested in clinical trials. Disease-modifying treatments might be at their most effective when initiated very early in the course of AD, before amyloid plaques and neurodegeneration become too widespread. Thus, biomarkers are needed that can detect AD in the predementia phase or, ideally, in presymptomatic individuals. In this Review, we present the rationales behind and the diagnostic performances of the core cerebrospinal fluid (CSF) biomarkers for AD, namely total tau, phosphorylated tau and the 42 amino acid form of amyloid-beta. These biomarkers reflect AD pathology, and are candidate markers for predicting future cognitive decline in healthy individuals and the progression to dementia in patients who are cognitively impaired. We also discuss emerging plasma and CSF biomarkers, and explore new proteomics-based strategies for identifying additional CSF markers. Furthermore, we outline the roles of CSF biomarkers in drug discovery and clinical trials, and provide perspectives on AD biomarker discovery and the validation of such markers for use in the clinic.

The clinical use of structural MRI in Alzheimer disease

Structural imaging based on magnetic resonance is an integral part of the clinical assessment of patients with suspected Alzheimer dementia. Prospective data on the natural history of change in structural markers from preclinical to overt stages of Alzheimer disease are radically changing how the disease is conceptualized, and will influence its future diagnosis and treatment. Atrophy of medial temporal structures is now considered to be a valid diagnostic marker at the mild cognitive impairment stage. Structural imaging is also included in diagnostic criteria for the most prevalent non-Alzheimer dementias, reflecting its value in differential diagnosis. In addition, rates of whole-brain and hippocampal atrophy are sensitive markers of neurodegeneration, and are increasingly used as outcome measures in trials of potentially disease-modifying therapies. Large multicenter studies are currently investigating the value of other imaging and nonimaging markers as adjuncts to clinical assessment in diagnosis and monitoring of progression. The utility of structural imaging and other markers will be increased by standardization of acquisition and analysis methods, and by development of robust algorithms for automated assessment.

Disease-modifying approach to the treatment of Alzheimer's disease: from alpha-secretase activators to gamma-secretase inhibitors and modulators

In the last decade, advances in understanding the neurobiology of Alzheimer's disease (AD) have translated into an increase in clinical trials assessing various potential AD treatments. At present, drugs used for the treatment of AD only slightly delay the inevitable symptomatic progression of the disease and do not affect the main neuropathological hallmarks of the disease, i.e. senile plaques and neurofibrillary tangles. Brain accumulation of oligomeric species of beta-amyloid (A beta) peptides, the principal components of senile plaques, is believed to play a crucial role in the development of AD. Based on this hypothesis, huge efforts are being made to identify drugs able to interfere with proteases regulating A beta formation from amyloid precursor protein (APP). Compounds that stimulate alpha-secretase, the enzyme responsible for non-amyloidogenic metabolism of APP, are being developed and one of these, EHT-0202, has recently commenced evaluation in a phase II study. The discovery of inhibitors of beta-secretase (memapsin-2, beta-amyloid cleaving enzyme-1 [BACE-1]), the enzyme that regulates the first step of amyloidogenic APP metabolism, has proved to be particularly difficult because of inherent medicinal chemistry issues and only one compound (CTS-21166) has proceeded to clinical testing. Conversely, several compounds that inhibit gamma-secretase, the pivotal enzyme that generates A beta, have been identified, the most advanced being LY-450139 (semagacestat), presently in phase III clinical development. There has been considerable disappointment over the failure of a phase III study of tarenflurbil, a compound believed to modulate the activity of gamma-secretase, after encouraging phase II findings. Nevertheless, other promising gamma-secretase modulators are being developed and are approaching clinical testing. All these therapeutic approaches increase the hope of slowing the rate of decline in patients with AD and modifying the natural history of this devastating disease within the next 5 years.

Aggressive course of disease in dementia

The rate of disease progression in Alzheimer's disease (AD) patients is variable. A significant proportion of AD patients appear to experience an aggressive course of disease, and this has a major impact on prognosis, the patients, and their caregivers and society in general. Here we review the current literature on an aggressive course of disease in dementia and how it can be recognized in clinical practice. We also discuss the options available for treating patients with this condition.

Beyond the neurotransmitter-focused approach in treating Alzheimer's disease: drugs targeting beta-amyloid and tau protein

Drugs currently used to treat Alzheimer's Disease (AD) have limited therapeutic value and do not affect the main neuropathological hallmarks of the disease, i.e., senile plaques and neurofibrillar tangles. Senile plaques are mainly formed of beta-amyloid (Abeta), a 42-aminoacid peptide. Neurofibrillar tangles are composed of paired helical filaments of hyperphosphorylated tau protein. New, potentially disease-modifying, therapeutic approaches are targeting Abeta and tau protein. Drugs directed against Abeta include active and passive immunization, that have been found to accelerate Abeta clearance from the brain. The most developmentally advanced monoclonal antibody directly targeting Abeta is bapineuzumab, now being studied in a large Phase III clinical trial. Compounds that interfere with proteases regulating Abeta formation from amyloid precursor protein (APP) are also actively pursued. The discovery of inhibitors of beta-secretase, the enzyme that regulates the first step of the amyloidogenic metabolism of APP, has been revealed to be particularly difficult due to inherent medicinal chemistry problems, and only one compound (CTS-21166) has reached clinical testing. Conversely, several compounds that inhibit gamma-secretase, the pivotal enzyme that generates Abeta, have been identified, the most advanced being LY-450139 (semagacestat), now in Phase III clinical development. Compounds that stimulate alpha-secretase, the enzyme responsible for the non-amyloidogenic metabolism of APP, are also being developed, and one of them, EHT-0202, has recently entered Phase II testing. Potent inhibitors of Abeta aggregation have also been identified, and one of such compounds, PBT-2, has provided encouraging neuropsychological results in a recently completed Phase II study. Therapeutic approaches directed against tau protein include inhibitors of glycogen synthase kinase- 3 (GSK-3), the enzyme responsible for tau phosphorylation and tau protein aggregation inhibitors. NP-12, a promising GSK-3 inhibitor, is being tested in a Phase II study, and methylthioninium chloride, a tau protein aggregation inhibitor, has given initial encouraging results in a 50-week study. With all these approaches on their way, the hope for disease-modifying therapy in this devastating disease may become a reality in the next 5 years.

Alzheimer's disease drug development: old problems require new priorities

Alzheimer's disease (AD) clinical drug development and patient care depend on rating instruments, research designs and methods, and translations of clinical trial (CT) results into the clinic without support from standardized protocols able to control (i) random measurement error intrusions into observations, (ii) inaccuracy and bias introduced by clinical evaluators, (iii) conformity of research sites to conditions of research protocols, (iv) the ability of the CT to model for practitioners the most effective use of the drug with individual patients, and (v) other factors able to invalidate research and patient care data. This relaxed attitude with regard to AD methods may be changing now with Alzheimer's Disease Neuroimaging Initiative (ADNI) evidence that carefully standardized protocols are needed to validate biomarkers for use in AD diagnosis, drug development, and patient care. In the fields of psychiatry and AD, recent studies have detected serious inaccuracies, imprecision, biases and compromises of study protocols able to invalidate CT outcome data and conclusions drawn from these data. This limited but troubling evidence reinforces ADNI calls for more detailed methodological protocols. Based on the limits to precision and accuracy associated with rated outcomes in CTs and patient care, we call for priority to be given to the qualification and use of biomarkers as outcome variables in AD drug development and patient care and, to insure effective uses of biomarkers, to development of protocol guided practices being modeled in ADNI research. To meet clinical pharmacology's therapeutic aims we conclude that AD CTs need to set for clinicians the conditions of use of drugs shown efficacious, biomarker surrogate endpoints as drug targets, and not to function merely as tests for efficacy conducted under field conditions determined by current clinical practices.

Cholinesterase inhibition: is there evidence for disease-modifying effects?

BACKGROUND

Cholinesterase inhibitors are broadly established as first-line symptomatic therapy for Alzheimer's disease (AD). Symptomatic effects are mediated by the inhibition of acetyl- and/or butyryl-cholinesterase (AChE and/or BuChE) - the enzymes that degrade acetylcholine (ACh) in the synapse. However, ACh is also found outside the synapse ('extracellular ACh') where, among other activities, it plays a role in controlling inflammation and might impact on pathological changes. OBJECTIVE/SCOPE: New data and clinical findings are reviewed and discussed to build a preliminary case for possible disease-modifying effects of cholinesterase inhibition.

FINDINGS

Trials seeking to demonstrate disease-modifying effects in subjects with mild cognitive impairment failed to reach their primary endpoints, but these failures might relate to aspects of trial methods and analyses. A re-analysis of one of these trials, using a more sensitive model controlling for factors that predict progression to AD, showed a significant delay in progression to AD with dual cholinesterase inhibition over 3 to 4 years. Taken with other evidence, it is plausible that cholinesterase inhibition might contribute to disease modification. The detection of putative disease-modifying effects may be most easily implemented in certain patient subpopulations, and genotyping studies suggest a particular role for BuChE.

CONCLUSION

Long-term inhibition of BuChE might be especially important when exploring any disease-modifying effects of cholinesterase inhibitors. Elucidation of the mechanisms involved could provide insights leading to the development of new treatments that modify the development and progression of AD.