A Machine Learning Approach to Identify a Circulating MicroRNA Signature for Alzheimer Disease

BACKGROUND

Accurate diagnosis of Alzheimer disease (AD) involving less invasive molecular procedures and at reasonable cost is an unmet medical need. We identified a serum miRNA signature for AD that is less invasive than a measure in cerebrospinal fluid.

METHODS

From the Oxford Project to Investigate Memory and Aging (OPTIMA) study, 96 serum samples were profiled by a multiplex (>500 analytes) microRNA (miRNA) reverse transcription quantitative PCR analysis, including 51 controls, 32 samples from patients with AD, and 13 samples from patients with mild cognitive impairment (MCI). Clinical diagnosis of a subset of AD and the controls was confirmed by postmortem (PM) histologic examination of brain tissue. In a machine learning approach, the AD and control samples were split 70:30 as the training and test cohorts. A multivariate random forest statistical analysis was applied to construct and test a miRNA signature for AD identification. In addition, the MCI participants were included in the test cohort to assess whether the signature can identify early AD patients.

RESULTS

A 12-miRNA signature for AD identification was constructed in the training cohort, demonstrating 76.0% accuracy in the independent test cohort with 90.0% sensitivity and 66.7% specificity. The signature, however, was not able to identify MCI participants. With a subset of AD and control participants with PM-confirmed diagnosis status, a separate 12-miRNA signature was constructed. Although sample size was limited, the PM-confirmed signature demonstrated improved accuracy of 85.7%, largely owing to improved specificity of 80.0% with comparable sensitivity of 88.9%.

CONCLUSION

Although additional and more diverse cohorts are needed for further clinical validation of the robustness, the miRNA signature appears to be a promising blood test to diagnose AD.

Understanding health-care outcomes of older people with cognitive impairment and/or dementia admitted to hospital: a mixed-methods study

Background

Cognitive impairment is common in older people admitted to hospital, but previous research has focused on single conditions.

Objective

This project sits in phase 0/1 of the Medical Research Council Framework for the Development and Evaluation of Complex Interventions. It aims to develop an understanding of current health-care outcomes. This will be used in the future development of a multidomain intervention for people with confusion (dementia and cognitive impairment) in general hospitals. The research was conducted from January 2015 to June 2018 and used data from people admitted between 2012 and 2013.

Design

For the review of outcomes, the systematic review identified peer-reviewed quantitative epidemiology measuring prevalence and associations with outcomes. Screening for duplication and relevance was followed by full-text review, quality assessment and a narrative review (141 papers). A survey sought opinion on the key outcomes for people with dementia and/or confusion and their carers in the acute hospital (n = 78). For the analysis of outcomes including cost, the prospective cohort study was in a medical admissions unit in an acute hospital in one Scottish health board covering 10% of the Scottish population. The participants (n = 6724) were older people (aged ≥ 65 years) with or without a cognitive spectrum disorder who were admitted as medical emergencies between January 2012 and December 2013 and who underwent a structured nurse assessment. ‘Cognitive spectrum disorder’ was defined as any combination of delirium, known dementia or an Abbreviated Mental Test score of < 8 out of 10 points. The main outcome measures were living at home 30 days after discharge, mortality within 2 years of admission, length of stay, re-admission within 2 years of admission and cost.

Data sources

Scottish Morbidity Records 01 was linked to the Older Persons Routine Acute Assessment data set.

Results

In the systematic review, methodological heterogeneity, especially concerning diagnostic criteria, means that there is significant overlap in conditions of patients presenting to general hospitals with confusion. Patients and their families expect that patients are discharged in the same or a better condition than they were in on admission or, failing that, that they have a satisfactory experience of their admission. Cognitive spectrum disorders were present in more than one-third of patients aged ≥ 65 years, and in over half of those aged ≥ 85 years. Outcomes were worse in those patients with cognitive spectrum disorders than in those without: length of stay 25.0 vs. 11.8 days, 30-day mortality 13.6% vs. 9.0%, 1-year mortality 40.0% vs. 26.0%, 1-year mortality or re-admission 62.4% vs. 51.5%, respectively (all p < 0.01). There was relatively little difference by cognitive spectrum disorder type; for example, the presence of any cognitive spectrum disorder was associated with an increased mortality over the entire period of follow-up, but with different temporal patterns depending on the type of cognitive spectrum disorder. The cost of admission was higher for those with cognitive spectrum disorders, but the average daily cost was lower.

Limitations

A lack of diagnosis and/or standardisation of diagnosis for dementia and/or delirium was a limitation for the systematic review, the quantitative study and the economic study. The economic study was limited to in-hospital costs as data for social or informal care costs were unavailable. The survey was conducted online, limiting its reach to older carers and those people with cognitive spectrum disorders.

Conclusions

Cognitive spectrum disorders are common in older inpatients and are associated with considerably worse health-care outcomes, with significant overlap between individual cognitive spectrum disorders. This suggests the need for health-care systems to systematically identify and develop care pathways for older people with cognitive spectrum disorders, and avoid focusing on only condition-specific pathways.

Future work

Development and evaluation of a multidomain intervention for the management of patients with cognitive spectrum disorders in hospital.

Study registration

This study is registered as PROSPERO CRD42015024492.

Funding

This project was funded by the National Institute for Health Research (NIHR) Health Services and Delivery Research programme and will be published in full in Health Services and Delivery Research; Vol. 9, No. 8. See the NIHR Journals Library website for further project information.

Minocycline at 2 Different Dosages vs Placebo for Patients With Mild Alzheimer Disease: A Randomized Clinical Trial

Question

Can 2 years of minocycline treatment modify the course of mild Alzheimer disease?

Findings

In this randomized clinical trial that included 544 participants, 24 months of minocycline treatment did not significantly delay progression of functional and cognitive impairment compared with placebo.

Meaning

Minocycline is not a candidate for disease modification for patients with symptomatic Alzheimer disease.

Importance

There are no disease-modifying treatments for Alzheimer disease (AD), the most common cause of dementia. Minocycline is anti-inflammatory, protects against the toxic effects of β-amyloid in vitro and in animal models of AD, and is a credible repurposed treatment candidate.

Objective

To determine whether 24 months of minocycline treatment can modify cognitive and functional decline in patients with mild AD.

Design, Setting, and Participants

Participants were recruited into a double-blind randomized clinical trial from May 23, 2014, to April 14, 2016, with 24 months of treatment and follow-up. This multicenter study in England and Scotland involved 32 National Health Service memory clinics within secondary specialist services for people with dementia. From 886 screened patients, 554 patients with a diagnosis of mild AD (Standardised Mini-Mental State Examination [sMMSE] score ≥24) were randomized.

Interventions

Participants were randomly allocated 1:1:1 in a semifactorial design to receive minocycline (400 mg/d or 200 mg/d) or placebo for 24 months.

Main Outcomes and Measures

Primary outcome measures were decrease in sMMSE score and Bristol Activities of Daily Living Scale (BADLS), analyzed by intention-to-treat repeated-measures regression.

Results

Of 544 eligible participants (241 women and 303 men), the mean (SD) age was 74.3 (8.2) years, and the mean (SD) sMMSE score was 26.4 (1.9). Fewer participants completed 400-mg minocycline hydrochloride treatment (28.8% [53 of 184]) than 200-mg minocycline treatment (61.9% [112 of 181]) or placebo (63.7% [114 of 179]; P < .001), mainly because of gastrointestinal symptoms (42 in the 400-mg group, 15 in the 200-mg group, and 10 in the placebo group; P < .001), dermatologic adverse effects (10 in the 400-mg group, 5 in the 200-mg group, and 1 in the placebo group; P = .02), and dizziness (14 in the 400-mg group, 3 in the 200-mg group, and 1 in the placebo group; P = .01). Assessment rates were lower in the 400-mg group: 68.4% (119 of 174 expected) for sMMSE at 24 months compared with 81.8% (144 of 176) for the 200-mg group and 83.8% (140 of 167) for the placebo group. Decrease in sMMSE scores over 24 months in the combined minocycline group was similar to that in the placebo group (4.1 vs 4.3 points). The combined minocycline group had mean sMMSE scores 0.1 points higher than the placebo group (95% CI, −1.1 to 1.2; P = .90). The decrease in mean sMMSE scores was less in the 400-mg group than in the 200-mg group (3.3 vs 4.7 points; treatment effect = 1.2; 95% CI, −0.1 to 2.5; P = .08). Worsening of BADLS scores over 24 months was similar in all groups: 5.7 in the 400-mg group, 6.6 in the 200-mg group, and 6.2 in the placebo groups (treatment effect for minocycline vs placebo = –0.53; 95% CI, −2.4 to 1.3; P = .57; treatment effect for 400 mg vs 200 mg of minocycline = –0.31; 95% CI, −0.2 to 1.8; P = .77). Results were similar in different patient subgroups and in sensitivity analyses adjusting for missing data.

Conclusions and Relevance

Minocycline did not delay the progress of cognitive or functional impairment in people with mild AD during a 2-year period. This study also found that 400 mg of minocycline is poorly tolerated in this population.

Trial Registration

isrctn.org Identifier: ISRCTN16105064

Genetic meta-analysis of diagnosed Alzheimer's disease identifies new risk loci and implicates Aβ, tau, immunity and lipid processing

Risk for late-onset Alzheimer's disease (LOAD), the most prevalent dementia, is partially driven by genetics. To identify LOAD risk loci, we performed a large genome-wide association meta-analysis of clinically diagnosed LOAD (94,437 individuals). We confirm 20 previous LOAD risk loci and identify five new genome-wide loci (IQCK, ACE, ADAM10, ADAMTS1, and WWOX), two of which (ADAM10, ACE) were identified in a recent genome-wide association (GWAS)-by-familial-proxy of Alzheimer's or dementia. Fine-mapping of the human leukocyte antigen (HLA) region confirms the neurological and immune-mediated disease haplotype HLA-DR15 as a risk factor for LOAD. Pathway analysis implicates immunity, lipid metabolism, tau binding proteins, and amyloid precursor protein (APP) metabolism, showing that genetic variants affecting APP and Aβ processing are associated not only with early-onset autosomal dominant Alzheimer's disease but also with LOAD. Analyses of risk genes and pathways show enrichment for rare variants (P = 1.32 × 10-7), indicating that additional rare variants remain to be identified. We also identify important genetic correlations between LOAD and traits such as family history of dementia and education.

A Validation Study of Vascular Cognitive Impairment Genetics Meta-Analysis Findings in an Independent Collaborative Cohort

Vascular cognitive impairment (VCI), including its severe form, vascular dementia (VaD), is the second most common form of dementia. The genetic etiology of sporadic VCI remains largely unknown. We previously conducted a systematic review and meta-analysis of all published genetic association studies of sporadic VCI prior to 6 July 2012, which demonstrated that APOE (ɛ4, ɛ2) and MTHFR (rs1801133) variants were associated with susceptibility for VCI. De novo genotyping was conducted in a new independent relatively large collaborative European cohort of VaD (nmax = 549) and elderly non-demented samples (nmax = 552). Where available, genotype data derived from Illumina's 610-quad array for 1210 GERAD1 control samples were also included in analyses of genes examined. Associations were tested using the Cochran-Armitage trend test: MTHFR rs1801133 (OR = 1.36, 95% CI 1.16-1.58, p = <0.0001), APOE rs7412 (OR = 0.62, 95% CI 0.42-0.90, p = 0.01), and APOE rs429358 (OR = 1.59, 95% CI 1.17-2.16, p = 0.003). Association was also observed with APOE epsilon alleles; ɛ4 (OR = 1.85, 95% CI 1.35-2.52, p = <0.0001) and ɛ2 (OR = 0.67, 95% CI 0.46-0.98, p = 0.03). Logistic regression and Bonferroni correction in a subgroup of the cohort adjusted for gender, age, and population maintained the association of APOE rs429358 and ɛ4 allele.

Correlates and Predictors of Self-reported Psychological and Physical Morbidity in Chronic Caregiver Stress

An investigation was conducted to explore: (1) whether psychological and physical morbidity share similar psychosocial determinants; (2) the long-term stability of these determinants; and (3) the role of neuroticism in predicting psychological and physical morbidity. Fifty spousal caregivers of dementia patients were recruited into a 12-month study. Participants were followed up at six-monthly interva ls during which they completed scales measuring psychosocial mediators, psychological morbidity, physical morbidity and neuroticism. Psychological morbidity was influenced primarily by indices of coping and neuroticism. Physical morbidity was influenced primarily by indices of psychological morbidity (increased psychological morbidity was associated with perceptions of greater physical morbidity). Neuroticism exhibited significant cross-sectional and longitudinal relationships with the indices of psychological morbidity, but only cross-sectional relationships with the indices of physical morbidity.

Brain health: the importance of recognizing cognitive impairment: an IAGG consensus conference

Cognitive impairment creates significant challenges for patients, their families and friends, and clinicians who provide their health care. Early recognition allows for diagnosis and appropriate treatment, education, psychosocial support, and engagement in shared decision-making regarding life planning, health care, involvement in research, and financial matters. An IAGG-GARN consensus panel examined the importance of early recognition of impaired cognitive health. Their major conclusion was that case-finding by physicians and health professionals is an important step toward enhancing brain health for aging populations throughout the world. This conclusion is in keeping with the position of the United States' Centers for Medicare and Medicaid Services that reimburses for detection of cognitive impairment as part the of Medicare Annual Wellness Visit and with the international call for early detection of cognitive impairment as a patient's right. The panel agreed on the following specific findings: (1) validated screening tests are available that take 3 to 7 minutes to administer; (2) a combination of patient- and informant-based screens is the most appropriate approach for identifying early cognitive impairment; (3) early cognitive impairment may have treatable components; and (4) emerging data support a combination of medical and lifestyle interventions as a potential way to delay or reduce cognitive decline.

Cerebrospinal fluid biomarkers distinguish postmortem-confirmed Alzheimer's disease from other dementias and healthy controls in the OPTIMA cohort

Cerebrospinal fluid (CSF) amyloid-β (Aβ) and tau have been studied as markers of Alzheimer's disease (AD). Combined Aβ42 and t-tau distinguishes AD from healthy controls with a sensitivity and specificity (sens/spec) near 89% across studies. This study examined these markers in the homogeneous OPTIMA cohort, using extensive longitudinal follow up and postmortem evaluation to confirm clinicopathological status. Baseline CSF was analyzed from 227 participants with AD (97% autopsy-confirmed), mild cognitive impairment (MCI; 73% confirmed), other dementia syndrome (ODS; 100% confirmed), and controls (CTL; 27% confirmed, follow up approximately 9-13 years). Biomarker concentrations were analyzed using validated ELISAs. AD patients had lower CSF Aβ42 and higher t-tau, p-tau, t-tau/Aβ42, and t-tau/Aβ40 compared to CTLs, with MCI intermediate. CTL and MCI participants who progressed to AD demonstrated more AD-like profiles. Aβ40, sAβPPα, and sAβPPβ were lower in AD compared to CTL. High-level discriminators of AD from CTL were t-tau/Aβ40 (AUROC 0.986, sens/spec of 92%/94%), p-tau/Aβ42 (AUROC 0.972, sens/spec of 94%/90%), and Aβ42 (AUROC 0.941, sens/spec of 88%). For discriminating AD from ODS, p-tau/Aβ42 demonstrated sens/spec of 88%/100% (95%/86% at the AD versus CTL cutoff) and Aβ42 demonstrated sens/spec of 84%/100% (88%/100% at the AD versus CTL cutoff). In a well-characterized, homogeneous population, a single cutoff for baseline CSF Aβ and tau markers can distinguish AD with a high level of sens/spec compared to other studies. It may be important to characterize sources of demographic and biological variability to support the effective use of CSF diagnostic assays in the broader AD population.

Cerebral amyloid angiopathy, subcortical white matter disease and dementia: literature review and study in OPTIMA

Cerebral amyloid angiopathy (CAA) is of increasing clinical and research interest as the ability to detect it and its consequences by neuroimaging in living subjects has advanced. There is also increasing interest in understanding its possible role in the development of intracerebral hemorrhage, Alzheimer's disease (AD) and vascular dementia. In this article, the literature on this subject is reviewed and novel findings relating CAA to subcortical white matter damage in 224 subjects in the Oxford project to Investigate Memory and Ageing (OPTIMA) are reported. The relationship between CAA and subcortical tissue damage in the OPTIMA subjects was found to be critically dependent on ApoE genotype, there being a positive relationship between measures of CAA and subcortical small vessel disease in ApoEε4 carriers and a significant negative relationship in ApoEε2 carriers. These findings draw attention, as have many other studies, to the importance of ApoE genotype as a major risk factor not only for dementia but also for damage to blood vessels in the aging brain.

The use of biomarkers for the etiologic diagnosis of MCI in Europe: an EADC survey

We investigated the use of Alzheimer's disease (AD) biomarkers in European Alzheimer's Disease Consortium centers and assessed their perceived usefulness for the etiologic diagnosis of mild cognitive impairment (MCI). We surveyed availability, frequency of use, and confidence in diagnostic usefulness of markers of brain amyloidosis (amyloid positron emission tomography [PET], cerebrospinal fluid [CSF] Aβ42) and neurodegeneration (medial temporal atrophy [MTA] on MR, fluorodeoxyglucose positron emission tomography [FDG-PET], CSF tau). The most frequently used biomarker is visually rated MTA (75% of the 37 responders reported using it "always/frequently") followed by CSF markers (22%), FDG-PET (16%), and amyloid-PET (3%). Only 45% of responders perceive MTA as contributing to diagnostic confidence, where the contribution was rated as "moderate". Seventy-nine percent of responders felt "very/extremely" comfortable delivering a diagnosis of MCI due to AD when both amyloid and neuronal injury biomarkers were abnormal (P < .02 versus any individual biomarker). Responders largely agreed that a combination of amyloidosis and neuronal injury biomarkers was a strongly indicative AD signature.

Reporting standards for studies of diagnostic test accuracy in dementia: The STARDdem Initiative

OBJECTIVE

To provide guidance on standards for reporting studies of diagnostic test accuracy for dementia disorders.

METHODS

An international consensus process on reporting standards in dementia and cognitive impairment (STARDdem) was established, focusing on studies presenting data from which sensitivity and specificity were reported or could be derived. A working group led the initiative through 4 rounds of consensus work, using a modified Delphi process and culminating in a face-to-face consensus meeting in October 2012. The aim of this process was to agree on how best to supplement the generic standards of the STARD statement to enhance their utility and encourage their use in dementia research.

RESULTS

More than 200 comments were received during the wider consultation rounds. The areas at most risk of inadequate reporting were identified and a set of dementia-specific recommendations to supplement the STARD guidance were developed, including better reporting of patient selection, the reference standard used, avoidance of circularity, and reporting of test-retest reliability.

CONCLUSION

STARDdem is an implementation of the STARD statement in which the original checklist is elaborated and supplemented with guidance pertinent to studies of cognitive disorders. Its adoption is expected to increase transparency, enable more effective evaluation of diagnostic tests in Alzheimer disease and dementia, contribute to greater adherence to methodologic standards, and advance the development of Alzheimer biomarkers.

Practical detection of a definitive biomarker panel for Alzheimer's disease; comparisons between matched plasma and cerebrospinal fluid

Previous mass spectrometry analysis of cerebrospinal fluid (CSF) has allowed the identification of a panel of molecular markers that are associated with Alzheimer's disease (AD). The panel comprises Amyloid beta, Apolipoprotein E, Fibrinogen alpha chain precursor, Keratin type I cytoskeletal 9, Serum albumin precursor, SPARC-like 1 protein and Tetranectin. Here we report the development and implementation of immunoassays to measure the abundance and diagnostic capacity of these putative biomarkers in matched lumbar CSF and blood plasma samples taken in life from individuals confirmed at post-mortem as suffering from AD (n = 10) and from screened 'cognitively healthy' subjects (n = 18). The inflammatory components of Alzheimer's disease were also investigated. Employment of supervised learning techniques permitted examination of the interrelated expression patterns of the putative biomarkers and identified inflammatory components, resulting in biomarker panels with a diagnostic accuracy of 87.5% and 86.7% for the plasma and CSF datasets respectively. This is extremely important as it offers an ideal high-throughput and relatively inexpensive population screening approach. It appears possible to determine the presence or absence of AD based on our biomarker panel and it seems likely that a cheap and rapid blood test for AD is feasible.

Single-domain amnestic mild cognitive impairment identified by cluster analysis predicts Alzheimer's disease in the european prospective DESCRIPA study

BACKGROUND/AIMS

To identify prodromal Alzheimer's disease (AD) subjects using a data-driven approach to determine cognitive profiles in mild cognitive impairment (MCI).

METHODS

A total of 881 MCI subjects were recruited from 20 memory clinics and followed for up to 5 years. Outcome measures included cognitive variables, conversion to AD, and biomarkers (e.g. CSF, and MRI markers). Two hierarchical cluster analyses (HCA) were performed to identify clusters of subjects with distinct cognitive profiles. The first HCA included all subjects with complete cognitive data, whereas the second one selected subjects with very mild MCI (MMSE ≥28). ANOVAs and ANCOVAs were computed to examine whether the clusters differed with regard to conversion to AD, and to AD-specific biomarkers.

RESULTS

The HCAs identified 4-cluster solutions that best reflected the sample structure. One cluster (aMCIsingle) had a significantly higher conversion rate (19%), compared to subjective cognitive impairment (SCI, p < 0.0001), and non-amnestic MCI (naMCI, p = 0.012). This cluster was the only one showing a significantly different biomarker profile (Aβ42, t-tau, APOE ε4, and medial temporal atrophy), compared to SCI or naMCI.

CONCLUSION

In subjects with mild MCI, the single-domain amnestic MCI profile was associated with the highest risk of conversion, even if memory impairment did not necessarily cross specific cut-off points. A cognitive profile characterized by isolated memory deficits may be sufficient to warrant applying prevention strategies in MCI, whether or not memory performance lies below specific z-scores. This is supported by our preliminary biomarker analyses. However, further analyses with bigger samples are needed to corroborate these findings.

The association between APOE ε4 and Alzheimer-type dementia among memory clinic patients is confined to those with a higher education. The DESCRIPA Study

We assessed the interaction between the APOE ε4 allele and education level in the etiology of Alzheimer's disease (AD) among memory clinic patients from the multicenter DESCRIPA study. Subjects (n = 544) were followed for 1 to 5 years. We used Cox's stratified survival modeling, adjusted for age, gender, and center. APOE ε4 predicted the onset of AD-type dementia in middle (HR 3.45 95% CI 1.79-6.65, n = 222) and high (HR 3.67 95% CI 1.36-9.89, n = 139) but not in low educated subjects (HR 0.81, 95% CI 0.38-1.72, n = 183). This suggests that mechanisms in developing Alzheimer-type dementia may differ between educational groups that raises questions related to Alzheimer-type dementia prevention.

Dysfunction of the mTOR pathway is a risk factor for Alzheimer's disease

Background

The development of disease-modifying therapies for Alzheimer’s disease is hampered by our lack of understanding of the early pathogenic mechanisms and the lack of early biomarkers and risk factors.

We have documented the expression pattern of mTOR regulated genes in the frontal cortex of Alzheimer’s disease patients. We have also examined the functional integrity of mTOR signaling in peripheral lymphocytes in Alzheimer’s disease patients relative to healthy controls.

Results

In the brain mTOR is seen to control molecular functions related to cell cycle regulation, cell death and several metabolic pathways. These downstream elements of the mTOR signaling cascade are deregulated in the brain of Alzheimer’s disease patients well before the development of pathology. This dysregulation of the mTOR downstream signaling cascade is not restricted to the brain but appears to be systemic and can be detected in peripheral lymphocytes as a reduced Rapamycin response.

Conclusions

The dysfunction of the signaling pathways downstream of mTOR may represent a risk factor for Alzheimer’s disease and is independent of the ApoE status of the patients.

We have also identified the molecular substrates of the beneficial effects of Rapamycin on the nervous system. We believe that these results can further inform the development of clinical predictive tests for the risk of Alzheimer’s disease in patients with mild cognitive impairment.

An assessment of neurocognitive speed in relation to frailty

OBJECTIVES

to evaluate the relationship between neurocognitive speed (NCS) and frailty; to consider how this relationship is affected by how frailty is operationalised.

DESIGN

secondary analysis of the baseline cohort of the Oxford Project To Investigate Memory and Aging (OPTIMA), a longitudinal observational cohort.

SUBJECTS

of 388 participants who underwent a comprehensive intake assessment followed by an annual follow-up for at least 3 years, data on all measures were available on 164 people.

MEASUREMENTS

NCS was defined as a combined score of <18 on the pattern comparison test (<11 is abnormal) and letter comparison test (<7 is abnormal). Frailty was defined from a modified Phenotype model, the Edmonton Frailty Scales (EFS) and a frailty index (FI); the latter two were adapted here to exclude cognitive measures.

RESULTS

in multivariate logistic (NCS as < or ≥18) and linear regression (NCS as continuous variable), only the FI (OR = 0.87) was significant (P < 0.05). When all frailty measures were included in the multivariate analysis only, FI (OR = 0.88) was significant (P < 0.05). Mini-mental Status Examination remained significantly related to NCS throughout all analysis.

CONCLUSION

NCS slows with increasing frailty as shown with the FI.

Identification of SPARC-like 1 protein as part of a biomarker panel for Alzheimer's disease in cerebrospinal fluid

We have used proteomic fingerprinting to investigate diagnosis of Alzheimer's disease (AD). Samples of lumbar cerebrospinal fluid (CSF) from clinically-diagnosed AD cases (n = 33), age-matched controls (n = 20), and mild cognitive impairment (MCI) patients (n = 10) were used to obtain proteomic profiles, followed by bioinformatic analysis that generated a set of potential biomarkers in CSF samples that could discriminate AD cases from controls. The identity of the biomarker ions was determined using mass spectroscopy. The panel of seven peptide biomarker ions was able to discriminate AD patients from controls with a median accuracy of 95% (sensitivity 85%, specificity 97%). When this model was applied to an independent blind dataset from MCI patients, the intensity of signals was intermediate between the control and AD patients implying that these markers could potentially predict patients with early neurodegenerative disease. The panel were identified, in order of predictive ability, as SPARC-like 1 protein, fibrinogen alpha chain precursor, amyloid-β, apolipoprotein E precursor, serum albumin precursor, keratin type I cytoskeletal 9, and tetranectin. The 7 ion ANN model was further validated using an independent cohort of samples, where the model was able to classify AD cases from controls with median accuracy of 84.5% (sensitivity 93.3%, specificity 75.7%). Validation by immunoassay was performed on the top three identified markers using the discovery samples and an independent sample cohort which was from postmortem confirmed AD patients (n = 17).

Is MRI better than CT for detecting a vascular component to dementia? A systematic review and meta-analysis

BACKGROUND

Identification of causes of dementia soon after symptom onset is important, because appropriate treatment of some causes of dementia can slow or halt its progression or enable symptomatic treatment where appropriate. The accuracy of MRI and CT, and whether MRI is superior to CT, in detecting a vascular component to dementia in autopsy confirmed and clinical cohorts of patients with VaD, combined AD and VaD ("mixed dementia"), and AD remain unclear. We conducted a systematic review and meta-analysis to investigate this question.

METHODS

We searched eight databases and screened reference lists to identify studies addressing the review question. We assessed study quality using QUADAS. We estimated summary diagnostic accuracy according to imaging finding, and ratios of diagnostic odds ratios (RDORs) for MRI versus CT and high versus low risk of bias.

RESULTS

We included 7 autopsy and 31 non-autopsy studies. There was little evidence that selective patient enrolment and risk of incorporation bias impacted on diagnostic accuracy (p = 0.12 to 0.95). The most widely reported imaging finding was white matter hyperintensities. For CT (11 studies) summary sensitivity and specificity were 71% (95% CI 53%-85%) and 55% (44%-66%). Corresponding figures for MRI (6 studies) were 95% (87%-98%) and 26% (12%-50%). General infarcts was the most specific imaging finding on MRI (96%; 95% CI 94%-97%) and CT (96%; 93%-98%). However, sensitivity was low for both MRI (53%; 36%-70%) and CT (52%; 22% to 80%). No imaging finding had consistently high sensitivity. Based on non-autopsy studies, MRI was more accurate than CT for six of seven imaging findings, but confidence intervals were wide.

CONCLUSION

There is insufficient evidence to suggest that MRI is superior to CT with respect to identifying cerebrovascular changes in autopsy-confirmed and clinical cohorts of VaD, AD, and 'mixed dementia'.

Visual search in mild cognitive impairment: a longitudinal study

In the study of Alzheimer's disease, a multidisciplinary research approach has identified significant abnormality in several areas of visual and visual attention-related brain function in addition to those typically measured as part of clinical diagnosis. This raises the possibility that a similar approach applied to amnestic mild cognitive impairment (aMCI) will increase our understanding of its theoretical and clinical constructs, particularly if functions whose integrity is heterogeneous with respect to etiological outcome can be found. In this study we examined visual search performance (the brain's ability to search effectively throughout the environment for a particular object) in aMCI compared to healthy aging. Cross-sectionally, visual search performance in aMCI was significantly poorer than in healthy aging, with greater intra-group performance heterogeneity in the aMCI compared to the healthy older adult group. This outcome illustrates that although individuals within an aMCI group ostensibly have the same condition they can differ substantially with respect to the integrity of aspects of brain function. Such findings may have implications for the clinical management of the individual patient. The results from the longitudinal aspect of this study also illustrate how heterogeneity in the performance of brain operations other than memory in aMCI may help to inform the likelihood of their developing dementia, as those patients who were diagnosed with dementia within 2.5 years of baseline measurement showed significantly poorer visual search performance compared to those who did not.

Regional differences in effects of APOE ε4 on cognitive impairment in non-demented subjects

BACKGROUND

The APOE ε4 allele is a risk factor for Alzheimer's disease (AD). APOE ε4 is common in non-demented subjects with cognitive impairment. In both healthy people and people with AD, its prevalence has a north-south gradient across Europe. In the present study, we investigated whether the relation between the APOE ε4 allele and cognitive impairment varied across Northern, Middle and Southern Europe. We also investigated whether a north-south gradient existed in subjects with subjective cognitive impairment (SCI), amnestic mild cognitive impairment (MCI) and non-amnestic MCI.

METHODS

Data from 16 centers across Europe were analyzed.

RESULTS

A north-south gradient in APOE ε4 prevalence existed in the total sample (62.7% for APOE ε4 carriers in the northern region, 42.1% in the middle region, and 31.5% in the southern region) and in subjects with SCI and amnestic MCI separately. Only in Middle Europe was the APOE ε4 allele significantly associated with poor performance on tests of delayed recall and learning, as well as with the amnestic subtype of MCI.

CONCLUSION

The APOE ε4 allele frequencies in subjects with SCI and amnestic MCI have a north-south gradient. The relation between the APOE ε4 allele and cognition is region dependent.

A comparison of screening tools for the assessment of mild cognitive impairment: preliminary findings

We report a pilot investigation into the utility of screening tools in Mild Cognitive Impairment (MCI). The Addenbrooke's Cognitive Examination-Revised (ACE-R), Montreal Cognitive Assessment (MoCA) and the novel Computer-Administered Neuropsychological Screen for Mild Cognitive Impairment (CANS-MCI) were administered to 20 elderly controls and 15 MCI cases. Non-parametric Mann-Whitney U-tests showed significant differences between groups (p < .0001) on the CANS-MCI and MoCA. The ACE-R and MoCA total scores showed high sensitivity (90%) to MCI. Area under the curve was consistently significant in discriminating controls and MCI for memory scores across all screening instruments. A useful profile of quantitative and qualitative information pertaining to cognitive functioning in MCI can be obtained with the MoCA, ACE-R, and CANS-MCI.

Lack of awareness of symptoms in people with dementia: the structural and functional basis

OBJECTIVE

To review studies investigating the brain correlates of unawareness of cognitive and behavioural symptoms in people with dementia.

DESIGN

A detailed search of the literature was conducted to include all the peer-reviewed studies published in English aimed at identifying the structural or functional brain correspondents of unawareness in dementia patients. Their results were interpreted in relation to the methodological differences in terms of type of dementia studied, the protocol adopted to measure lack of awareness, the imaging techniques employed, the experimental designs and statistical analyses performed.

RESULTS

Eighteen studies undertaken to explore the functional and structural correlates of unawareness of cognitive symptoms in dementia were identified. Although their results showed a disparate range of brain correlates, they were mainly localized in frontal and temporo-parietal regions.

CONCLUSIONS

Although the anatomical correlates of unawareness of disease in dementia have not yet been exhaustively explored, understanding the correlates of unawareness may also contribute to understand the brain correlates of self-awareness and self-reflection. We discuss the current knowledge base and consider potential future directions for research.

Cognitive lifestyle and long-term risk of dementia and survival after diagnosis in a multicenter population-based cohort

An active cognitive lifestyle has been linked to dementia incidence and survival, but the separate and combined effects of its subcomponents are not clear. Data were derived from the Medical Research Council Cognitive Function and Ageing Study, a population-based study of 13,004 individuals in England and Wales first interviewed in 1991-1992 and followed over a 10-year period for dementia incidence and 12 years for mortality. A Cognitive Lifestyle Score (CLS), defined as a composite of cognitive activity including education, occupational complexity, and social engagement, was available for 12,600 individuals in 3 stages of life. A higher CLS was protective of dementia (odds ratio = 0.6, 95% confidence interval: 0.4, 0.9). Sensitivity analyses found this main effect to be reliable and replicable even when considering just 2 components of the score, either education and occupation or education and late-life social engagement. No single CLS factor was associated with dementia incidence on its own. Survival differences did not reach statistical significance. Our data suggest that more years of education, as well as further stimulatory experiences in either midlife or late life. are necessary for a protective link with dementia incidence. There was little evidence of an effect of cognitive lifestyle on survival after dementia diagnosis.

Common variants at ABCA7, MS4A6A/MS4A4E, EPHA1, CD33 and CD2AP are associated with Alzheimer's disease

We sought to identify new susceptibility loci for Alzheimer's disease through a staged association study (GERAD+) and by testing suggestive loci reported by the Alzheimer's Disease Genetic Consortium (ADGC) in a companion paper. We undertook a combined analysis of four genome-wide association datasets (stage 1) and identified ten newly associated variants with P ≤ 1 × 10(-5). We tested these variants for association in an independent sample (stage 2). Three SNPs at two loci replicated and showed evidence for association in a further sample (stage 3). Meta-analyses of all data provided compelling evidence that ABCA7 (rs3764650, meta P = 4.5 × 10(-17); including ADGC data, meta P = 5.0 × 10(-21)) and the MS4A gene cluster (rs610932, meta P = 1.8 × 10(-14); including ADGC data, meta P = 1.2 × 10(-16)) are new Alzheimer's disease susceptibility loci. We also found independent evidence for association for three loci reported by the ADGC, which, when combined, showed genome-wide significance: CD2AP (GERAD+, P = 8.0 × 10(-4); including ADGC data, meta P = 8.6 × 10(-9)), CD33 (GERAD+, P = 2.2 × 10(-4); including ADGC data, meta P = 1.6 × 10(-9)) and EPHA1 (GERAD+, P = 3.4 × 10(-4); including ADGC data, meta P = 6.0 × 10(-10)).

Effect of tarenflurbil on cognitive decline and activities of daily living in patients with mild Alzheimer disease: a randomized controlled trial

CONTEXT

Amyloid-beta peptide (Abeta(42)) has been implicated in the pathogenesis of Alzheimer disease (AD). Tarenflurbil, a selective Abeta(42)-lowering agent, demonstrated encouraging results on cognitive and functional outcomes among mildly affected patients in an earlier phase 2 trial.

OBJECTIVE

To determine the efficacy, safety, and tolerability of tarenflurbil.

DESIGN, SETTING, AND PATIENTS

A multicenter, randomized, double-blind, placebo-controlled trial enrolling patients with mild AD was conducted at 133 trial sites in the United States between February 21, 2005, and April 30, 2008. Concomitant treatment with cholinesterase inhibitors or memantine was permitted.

INTERVENTION

Tarenflurbil, 800 mg, or placebo, administered twice a day.

MAIN OUTCOME MEASURES

Co-primary efficacy end points were the change from baseline to month 18 in total score on the subscale of the Alzheimer Disease Assessment Scale-Cognitive Subscale (ADAS-Cog, 80-point version) and Alzheimer Disease Cooperative Studies-activities of daily living (ADCS-ADL) scale. Additional prespecified slope analyses explored the possibility of disease modification.

RESULTS

Of the 1684 participants randomized, 1649 were included in the analysis, and 1046 completed the trial. Tarenflurbil had no beneficial effect on the co-primary outcomes (difference in change from baseline to month 18 vs placebo, based on least squares means: 0.1 for ADAS-Cog; 95% CI, -0.9 to 1.1; P = .86 and -0.5 for ADCS-ADL; 95% CI, -1.9 to 0.9; P = .48) using an intent-to-treat analysis. No significant differences occurred in the secondary outcomes. The ADAS-Cog score decreased by 7.1 points over 18 months. The tarenflurbil group had a small increase in frequency of dizziness, anemia, and infections.

CONCLUSION

Tarenflurbil did not slow cognitive decline or the loss of activities of daily living in patients with mild AD.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00105547.

Blood pressure, dementia and Alzheimer's disease: the OPTIMA longitudinal study

BACKGROUND/AIMS

Studies on the relation between blood pressure (BP), dementia and Alzheimer's disease (AD) have yielded inconsistent results, showing an association with high or low BP, or no association with BP. The study was designed to look at the longitudinal effect of BP on cognitive function.

METHODS

Participants were part of the OPTIMA longitudinal study of patients with dementia and agematched cognitively healthy controls. The Cambridge Cognitive Examination (CAMCOG) and BP were measured. We tested the dependence of CAMCOG scores on BP using generalised linear mixed models.

RESULTS

A total of 235 were cognitively healthy controls, 42 had mild cognitive impairment (MCI), 141 had AD, and 59 had other dementia syndrome (ODS). In AD patients, the rate of decline of CAMCOG scores showed an inverted U-shaped (non-linear) dependence on diastolic BP. High (110 mm Hg) and low (60 mm Hg) levels of diastolic BP were related to faster cognitive decline over 5 years of follow-up (z = -2.51, p = 0.012). CAMCOG scores also showed an inverted U-shaped dependence on pulse pressure (z = -2.29, p = 0.022).

CONCLUSION

High and low BP levels are related to faster cognitive decline in AD patients. This could have implications for the prevention and treatment of AD.

New insights into feature and conjunction search: II. Evidence from Alzheimer's disease

Deficits in inefficient visual search task performance in Alzheimer's disease (AD) have been linked both to a general depletion of attentional resources and to a specific difficulty in performing conjunction discriminations. It has been difficult to examine the latter proposal because the uniqueness of conjunction search as compared to other visual search tasks has remained a matter of debate. We explored both these claims by measuring pupil dilation, as a measure of resource application, while patients with AD performed a conjunction search task and two single-feature search tasks of similar difficulty in healthy individuals. Maximum pupil dilation in the AD group was greater during performance of the conjunction than the feature search tasks, although pupil response was indistinguishable for the three tasks in healthy controls. This, together with patients' false positive errors for the conjunction task, indicates an AD-specific deficit impacting upon the ability to combine information on multiple dimensions. In addition, maximum pupil dilation was no less for patients than the control group during task performance, which tends to oppose the concept of general resource depletion in AD. However, eye movement patterns in the patient group indicated that they were less able than controls to use organised strategies to assist with task performance. The data are therefore in keeping with a loss of access to resource-saving strategies, rather than a loss of resources per se, in AD. Moreover they demonstrate an additional processing mechanism in performing conjunction search compared with inefficient single-feature search.

New insights into feature and conjunction search: I. Evidence from pupil size, eye movements and ageing

Differences in the processing mechanisms underlying visual feature and conjunction search are still under debate, one problem being a common emphasis on performance measures (speed and accuracy) which do not necessarily provide insights to the underlying processing principles. Here, eye movements and pupil dilation were used to investigate sampling strategy and processing load during performance of a conjunction and two feature-search tasks, with younger (18-27 years) and healthy older (61-83 years) age groups compared for evidence of differential age-related changes. The tasks involved equivalent processing time per item, were controlled in terms of target-distractor similarity, and did not allow perceptual grouping. Close matching of the key tasks was confirmed by patterns of fixation duration and an equal number of saccades required to find a target. Moreover, moment-to-moment pupillary dilation was indistinguishable across the tasks for both age groups, suggesting that all required the same total amount of effort or resources. Despite matching, subtle differences in eye movement patterns occurred between tasks: the conjunction task required more saccades to reach a target-absent decision and involved shorter saccade amplitudes than the feature tasks. General age-related changes were manifested in an increased number of saccades and longer fixation durations in older than younger participants. In addition, older people showed disproportionately longer and more variable fixation durations for the conjunction task specifically. These results suggest a fundamental difference between conjunction and feature search: accurate target identification in the conjunction context requires more conservative eye movement patterns, with these further adjusted in healthy ageing. The data also highlight the independence of eye movement and pupillometry measures and stress the importance of saccades and strategy for understanding the processing mechanisms driving different types of visual search.

Endpoints for trials in Alzheimer's disease: a European task force consensus

Harmful consequences in health status caused by disease are referred to as outcomes, and in clinical studies the measures of these outcomes are called endpoints. A major challenge when deciding on endpoints is to represent the outcomes of interest accurately, and the accuracy of such representation is assessed through validation. Complex diseases like Alzheimer's disease have many different and interdependent outcomes. We present a consensus for endpoints to be used in clinical trials in Alzheimer's disease, agreed by a European task force under the auspices of the European Alzheimer Disease Consortium. We suggest suitable endpoints for primary and secondary prevention trials, for symptomatic and disease-modifying trials in very early, mild, and moderate Alzheimer's disease, and for trials in severe Alzheimer's disease. A clear and consensual definition of endpoints is crucial for the success of further clinical trials in the field and will allow comparison of data across studies.

Development of screening guidelines and clinical criteria for predementia Alzheimer's disease. The DESCRIPA Study

BACKGROUND

There is an urgent need to identify subjects with Alzheimer's disease (AD) in the predementia phase, but validated diagnostic approaches are currently lacking. In this paper, we present the background, design and methods of a study, which aims to develop clinical criteria for predementia AD. We also present baseline characteristics of the subjects included. The study was part of the multicentre DESCRIPA project, which is being conducted within the network of the European Alzheimer's Disease Consortium.

METHODS

Clinical criteria will be based on a prospective cohort study of non-demented subjects older than 55 years and referred to a memory clinic. At baseline, a number of markers and risk factors for AD were collected, including demographic variables, measures of performance in activities of daily living, cognitive, neuroimaging and genetic markers, and serum and cerebrospinal fluid markers. Subjects will be reassessed annually for 2-3 years, and we will evaluate which combination of variables best predicts AD-type dementia at follow-up.

RESULTS

Between 2003 and 2005, 881 subjects were included from 20 memory clinics. Subjects were on average 70.3 years old, and had 10.4 years of education. The average score on the Mini-Mental State Examination was 27.4.