Prodromal Stage Of Alzheimer's Disease Research Articles

Phosphodiesterase Type 5 Inhibitors in Men With Erectile Dysfunction and the Risk of Alzheimer Disease: A Cohort Study.

Repurposing phosphodiesterase type 5 inhibitors (PDE5Is) as drugs for Alzheimer disease (AD) risk reduction has shown promise based on animal studies. However, evidence in humans remains inconclusive. Therefore, we conducted a cohort study to evaluate the association between PDE5I initiation compared with nonuse and the risk of developing AD in men with erectile dysfunction (ED). Using electronic health records from IQVIA Medical Research Data UK (formerly known as the THIN database), we identified men aged ≥40 years with a new diagnosis of ED between 2000 and 2017. Individuals with a previous diagnosis of dementia, cognitive impairment, confusion, or prescription for dementia symptoms were excluded. The occurrence of incident AD was identified using diagnostic read codes. To minimize immortal-time bias, PDE5I initiation was treated as a time-varying exposure variable. Potential confounders were adjusted using inverse probability of treatment weighting based on propensity scores. Cox proportional hazard models were used to estimate the adjusted hazard ratio (HR) with 95% CIs. A secondary analysis explored the association between AD and the cumulative number of PDE5I prescriptions. Sensitivity analyses included lag (delay) periods of 1 and 3 years after cohort entry to address the prodromal stage of AD. The study included 269,725 men, with 1,119 newly diagnosed with AD during a median follow-up of 5.1 (interquartile range 2.9-8.9) years. The adjusted HR in PDE5I initiators compared with nonuse was 0.82 (95% CI 0.72-0.93). The associated risk of AD decreased in individuals issued >20 prescriptions: HR 0.56 (95% CI 0.43-0.73) for 21-50 prescriptions and HR 0.65 (95% CI 0.49-0.87) for >50 prescriptions. Sensitivity analysis with a 1-year lag period supported the primary findings (HR 0.82, 95% CI 0.72-0.94), but the results differed with the inclusion of a 3-year lag period (HR 0.93, 95% CI 0.80-1.08). PDE5I initiation in men with ED was associated with a lower risk of AD, particularly in those most frequently issued prescriptions. The differences between primary and sensitivity analyses highlight the need to explore the optimal lag period. To enhance the generalizability of our findings, a randomized controlled trial including both sexes and exploring various PDE5I doses would be beneficial to confirm the association between PDE5I and AD.

The Optimization of a Natural Language Processing Approach for the Automatic Detection of Alzheimer's Disease Using GPT Embeddings.

The development of noninvasive and cost-effective methods of detecting Alzheimer's disease (AD) is essential for its early prevention and mitigation. We optimize the detection of AD using natural language processing (NLP) of spontaneous speech through the use of audio enhancement techniques and novel transcription methodologies. Specifically, we utilized Boll Spectral Subtraction to improve audio fidelity and created transcriptions using state-of-the-art AI services-locally-based Wav2Vec and Whisper, alongside cloud-based IBM Cloud and Rev AI-evaluating their performance against traditional manual transcription methods. Support Vector Machine (SVM) classifiers were then trained and tested using GPT-based embeddings of transcriptions. Our findings revealed that AI-based transcriptions largely outperformed traditional manual ones, with Wav2Vec (enhanced audio) achieving the best accuracy and F-1 score (0.99 for both metrics) for locally-based systems and Rev AI (standard audio) performing the best for cloud-based systems (0.96 for both metrics). Furthermore, this study revealed the detrimental effects of interviewer speech on model performance in addition to the minimal effect of audio enhancement. Based on our findings, current AI transcription and NLP technologies are highly effective at accurately detecting AD with available data but struggle to classify probable AD and mild cognitive impairment (MCI), a prodromal stage of AD, due to a lack of training data, laying the groundwork for the future implementation of an automatic AD detection system.

Combination strategy employing BACE1 inhibitor and memantine to boost cognitive benefits in Alzheimer's disease therapy.

The β-secretase BACE1 initiates amyloid-β (Aβ) generation and represents a long-standing prime therapeutic target for the treatment of Alzheimer's disease (AD). However, BACE1 inhibitors tested to date in clinical trials have yielded no beneficial outcomes. In fact, prior BACE1 inhibitor trials targeted at ~ 50-90% Aβ reductions in symptomatic or prodromal AD stages have ended in the discontinuation due to futility and/or side effects, including cognitive worsening rather than expected improvement at the highest dose. We tested whether a combination strategy with the selective BACE1 inhibitor GRL-8234 and the FDA-approved symptomatic drug memantine may provide synergistic cognitive benefits within their safe dose range. The drug effects were evaluated in the advanced symptomatic stage of 5XFAD mice that developed extensive cerebral Aβ deposition. Chronic combination treatment with 33.4-mg/kg GRL-8234 and 10-mg/kg memantine, but not either drug alone, rescued cognitive deficits in 5XFAD mice at 12months of age (the endpoint after 60-day drug treatment), as assessed by the contextual fear conditioning, spontaneous alternation Y-maze and nest building tasks. Intact baseline performances of wild-type control mice on three cognitive paradigms demonstrated that combination treatment did not augment potential cognitive side effects of individual drugs. Biochemical and immunohistochemical examination showed that combination treatment did not synergistically reduce the β-amyloidogenic processing of amyloid precursor protein or Aβ levels in 5XFAD mouse brains. A combination strategy with BACE1 inhibitors and memantine may be able to increase the effectiveness of individual drugs within their safe dose range in AD therapy.

Abnormal dynamics of functional brain network in Apolipoprotein E ε4 carriers with mild cognitive impairment

<abstract> <p>As is well known, the Apolipoprotein E (APOE) ε4 allele is the most pertinent genetic hazardous element for Alzheimer's disease (AD). Mild cognitive impairment (MCI) is considered a prodromal stage of AD. How the APOE ε4 allele modulates functional connectivity of brain network in MCI group is a question worth exploring. At present, some studies have evaluated the relationship between APOE ε4 allele and static functional network connectivity (sFNC) for MCI individuals, while the relationship of dynamic FNC (dFNC) with APOE ε4 allele still remained puzzled. Thus, we aim to detect aberrant dFNC for APOE ε4 carriers in the MCI group. On the basis of the resting-state functional magnetic resonance imaging (rs-fMRI) data, seven intrinsic brain functional networks were first recognized by the group independent component analysis. Then, the technique of sliding window was employed to determine the dFNC, and two dFNC states were detected by the k-means clustering algorithm. Finally, three temporal properties of fraction time, mean dwell time as well as transition numbers in the dFNC states were investigated. The results found that the dFNC and temporal properties in APOE ε4 carriers were abnormal compared with those in APOE ε4 noncarriers. In detail, in the MCI group, compared with APOE ε4 noncarriers, carriers had 9 pairs of abnormal dFNC and had significant differences in all the three temporal properties of the two dFNC states. In addition, two pairs of dFNC were found significantly correlated with clinical measure. This detected abnormal dynamics of temporal properties and dFNC in APOE ε4 carriers were similar with that reported for AD patients in previous studies. These results may suggest that in the MCI group, APOE carriers are more at risk for AD compared to noncarriers. Our findings may offer novel insights into the mechanisms of abnormal brain reconfiguration for individuals at genetic risk for AD, which could also be regarded as biomarkers for the early identification of AD.</p> </abstract>

Hierarchical Graph Convolutional Network Built by Multiscale Atlases for Brain Disorder Diagnosis Using Functional Connectivity.

Functional connectivity network (FCN) data from functional magnetic resonance imaging (fMRI) is increasingly used for the diagnosis of brain disorders. However, state-of-the-art studies used to build the FCN using a single brain parcellation atlas at a certain spatial scale, which largely neglected functional interactions across different spatial scales in hierarchical manners. In this study, we propose a novel framework to perform multiscale FCN analysis for brain disorder diagnosis. We first use a set of well-defined multiscale atlases to compute multiscale FCNs. Then, we utilize biologically meaningful brain hierarchical relationships among the regions in multiscale atlases to perform nodal pooling across multiple spatial scales, namely "Atlas-guided Pooling (AP)." Accordingly, we propose a multiscale-atlases-based hierarchical graph convolutional network (MAHGCN), built on the stacked layers of graph convolution and the AP, for a comprehensive extraction of diagnostic information from multiscale FCNs. Experiments on neuroimaging data from 1792 subjects demonstrate the effectiveness of our proposed method in the diagnoses of Alzheimer's disease (AD), the prodromal stage of AD i.e., mild cognitive impairment (MCI), as well as autism spectrum disorder (ASD), with the accuracy of 88.9%, 78.6%, and 72.7%, respectively. All results show significant advantages of our proposed method over other competing methods. This study not only demonstrates the feasibility of brain disorder diagnosis using resting-state fMRI empowered by deep learning but also highlights that the functional interactions in the multiscale brain hierarchy are worth being explored and integrated into deep learning network architectures for a better understanding of the neuropathology of brain disorders. The codes for MAHGCN are publicly available at "https://github.com/MianxinLiu/ MAHGCN-code."

Memory dysfunction in mild cognitive impairment (MCI) and early Alzheimer disease (AD) dementia is closely associated with synapse loss, and shows significant correlation with pathological tau in synapses and inflammatory glial cell responses in postmortem human brain

AbstractBackgroundSynapse density loss is among the strongest histopathological correlates of dementia in AD. Prodromal stages of AD, comprising amnestic MCI and mild AD dementia, represent the most promising timepoints for interventions aimed at attaining efficacious neurobiological and clinical effects. Yet, the understanding of other contributing neuropathologic changes in these prodromal disease stages and their impact on early cognitive dysfunction remains limited.MethodsWe studied the visual cortex of 28 demented and non‐demented human brains who had died at Braak III‐IV stages of NFT pathology, and who showed a comparable β‐amyloid plaque burden and absence of NFT deposits in the studied brain region, and a group of age‐matched healthy controls. We used immunohistochemical analyses with artificial intelligence quantifications, expansion microscopy, synaptosome extractions, and Western blotting, to assess associations between antemortem MMSE scores and synapse densities, glial cell phenotypes, and pathological tau.ResultsWe found a significant loss of presynapses (Synapsin 1+), excitatory postsynapses (PSD95+), and colocalized synapses (Synapsin1‐PSD95+) in the brains of demented compared to non‐demented and controls. Moreover, we observed an association between excitatory synapse loss and memory dysfunction (MMSE score) as well as rate of disease progression (MMSE loss/time). MMSE scores were further associated with increase in tau oligomers (TOC1+) and phospho‐tau (AT270+) in synaptosomes, but not with 4G8+ β‐amyloid burden. Additionally, disease severity and rate of progression were significantly correlated with inflammatory glial changes.ConclusionsOur data suggest that excitatory synapse loss could serve as an early and robust neuropathologic correlate of disease severity and rate of progression from MCI stages of the disease, and be a closer and better determinant of cognitive decline than β‐amyloid and tau deposits. Moreover, early increases in soluble tau in synapses together with local inflammatory glial cell responses could drive development of incipient changes in memory function and serve as potential early biomarkers. Our results point to the importance of early detection and interventions aimed at synapse preservation from prodromal stages of AD, and suggest soluble tau and inflammatory glial cell changes as key targets in the early AD phases.

Identifying the optimal age to intervene in Alzheimer’s disease prevention trials: Validation of Emax modelling in sporadic Alzheimer’s disease

AbstractBackgroundMany clinical trials of disease‐modifying therapies which seek to delay or prevent Alzheimer’s disease (AD) currently exist. However, a limitation of these trials is the absence of considering the earliest age groups at which decline in cognition can be detected to guide optimal participant recruitment.Previous work has shown that in people with Down syndrome, Emax modelling can be used to identify the trajectory of cognitive decline in the preclinical and prodromal stages of AD. We aimed to validate Emaxmodelling to identify the earliest age of change in cognition in people who developed sporadic AD and compare these individuals to healthy controls without AD.MethodOur sample consisted of participants aged 65 years old from the Enquête Sante ́ Psychologique – Risques, Incidence et Traitement (ESPRIT) study. Participants were categorised into two groups based on whether they were ever diagnosed with possible and probable AD while enrolled in the study (n = 101) or did not receive a diagnosis of any subtype of dementia (n = 1392, our healthy control group). We included measures of general cognitive functioning (Mini Mental State Examination; MMSE), verbal fluency, visual memory (Benton Visual Retention Test) and executive functioning (Trail Making Test).ResultIn people with AD, the earliest decline in general cognitive functioning could be detected in the 67‐71 age band while verbal fluency appears to decline from the 41‐45 age band and visual memory in the 82‐86 age band according to our model. In healthy controls, general cognitive functioning shows early change in the 87‐91 age band while verbal fluency starts to decline in the 43‐47 age band and executive functioning in the 85‐89 age band. Models for Trail Making Models for people with AD and visual memory for controls were not well fitted to the data.ConclusionWe have shown that sensitivity to change depend on the primary outcome so authors designing trials need to ensure the research question, population and primary outcome are consistent. This has implications particularly for trials targeting the stages of disease before dementia diagnosis.

Empirical Project: Investigating the onset and trajectory of Alzheimer’s disease in Down syndrome

Three decades of data, collected at a community learning disability service in a region of the UK, are reported on. Participants included 579 people with Down syndrome (DS), who were followed up from baseline to the point of a dementia diagnosis, and in some cases until death. Since most people with DS develop Alzheimer’s disease (AD), the aim was to see whether certain neuropsychological measures were changing in the prodromal stages of AD, above that of normal ageing, to support timely diagnoses. Variables associated with earlier age at dementia onset and subsequent survival times were also assessed. Generalised linear mixed models in R were used to compute prodromal changes for 204 of the sample, who had more than two complete assessments. Regression and hazard regression models in SPSS were used for onset (n= 279) and survival times (n= 185), respectively. Results suggest that difficulties with lexical-retrieval and visual memory may be early indicators of later AD. Awareness of the level of intellectual disability appears essential, since profound disability produced ‘floor’ effects, which impacted on the possibility for later declines. Earlier age at first assessment and living with family were predictive of an earlier age at diagnosis, which then led to longer duration of life, post-diagnosis. Both earlyand late-onset epilepsy, and living in a long-stay hospital were associated with earlier mortality. Implications for clinical practice and research are discussed.

Early locus coeruleus degeneration impairs the longevity of fear memory in APPswe/PS1dE9 mice

AbstractBackgroundThe locus coeruleus (LC), a brainstem noradrenergic nucleus is known to modulate cognitive functions and behaviour. LC is one the first sites of appearance of misfolded tau protein which later develops into neurofibrillary tangles. Hyperphosphorylated tau and amyloid β are best protein correlates of cognitive decline in Alzheimer’s disease (AD). In early onset AD, subtle cognitive deficits develop <25 years before the patients develop dementia. Loss of LC neurons and its innervation has been found to be significantly associated with behavioural deficits observed during prodromal stage of AD. However, the extent and consequences of LC‐noradrenergic system degeneration during early stages of AD pathogenesis are still under investigation.MethodTo address this question, we have performed contextual fear conditioning (cFC) behavioural task to test fear memory in 2‐month‐old APPswe/PS1dE9 (APP/PS1) mice, a transgenic amyloidogenic model of AD. We further investigated the status of LC terminals and the distribution of β‐adrenoceptors (β‐AR) in the hippocampus using dopamine‐β‐hydroxylase (DBH), tyrosine hydroxylase (TH), and β‐AR immunohistochemistry respectively. Finally, we checked if stereotaxic delivery of β‐AR agonist to the hippocampus could rescue the impairments in long‐term fear memory.ResultOur study demonstrates that 2‐month‐old male but not female APP/PS1 mice exhibit impaired long‐term fear memory in cFC task. Immunohistochemical analysis of DBH and TH positive nerve terminals revealed loss of noradrenergic and dopaminergic terminals in male but not female APP/PS1 mice hippocampus. Further, male APP/PS1 mice were found to have low levels of β‐AR in the hippocampus and intra‐hippocampal administration of isoproterenol hydrochloride, a β‐AR agonist, immediately before cFC could restore long‐term contextual fear memory.ConclusionLC‐noradrenergic system degeneration displayed an inherent sex‐specific difference on longevity of fear memory with deficits occurring only in male APP/PS1 mice during early stages of AD.

Spectral power ratio as a measure of the EEG spectral power shift in mild cognitive impairment due to Alzheimer’s disease

AbstractBackgroundMarkers sensitive to brain changes at the transition from mild cognitive impairment (MCI) to dementia due to Alzheimer’s disease (AD) are needed for aiding prognosis and the selection of potential responders to novel interventional therapies. EEG markers may be advantageous due to their accessibility.Prior research suggests that AD is associated with a shift in the brain’s oscillatory activity from higher to lower frequencies which can be captured as changes in the EEG spectral power ratio (SPR: α + β /δ + θ), a measurement associated with executive function1. The aim of the present study is to extend these findings to the prodromal stage of AD, and test the association of the SPR with amyloid burden.MethodData was obtained from 31 participants, including 23 aMCI (17 amyloid positive: Aβ+aMCI) and 14 CU individuals. We compared the SPRs between Aβ+aMCI and CU individuals, and tested its correlation with composite scores of executive functions, learning and memory, dementia severity, as well as amyloid load in the Aβ+aMCI group. Test‐retest reliability of the SPR was also inspected and the SPR of MCI individuals with different amyloid status was explored in hypothesis generating analyses.ResultThe SPR was significantly lower in the Aβ+aMCI group compared to the CU group (p = 0.0271) and was significantly correlated with Executive Function scores (r = 0.5634). The SPR showed excellent test‐retest reliability (rAβ+aMCI = 0.8629 and rCU = 0.9786). Logistic regression suggested that aMCI participants with a lower SPR had an increased probability of a positive amyloid PET.ConclusionOur results extended previous findings in AD and suggested that the SPR may be sensitive to pathophysiological changes in aMCI individuals in a cognitively meaningful manner. Further research may confirm these findings and may explore the potential of this measure to aid in the classification of aMCI individuals according to their amyloid status.1. Benwell CSY, Davila‐Pérez P, Fried PJ, Jones RN, Travison TG, Santarnecchi E, Pascual‐Leone A, Shafi MM (2020) EEG spectral power abnormalities and their relationship with cognitive dysfunction in patients with Alzheimer’s disease and type 2 diabetes. Neurobiol Aging 85, 83‐95.

Not all regions are created equal: identifying regions and cell types associated with cognitive resilience in the AD‐BXD model population

AbstractBackgroundThe relationship between regional cell composition, brain pathology, and memory impairment in Alzheimer’s disease (AD) remains incompletely understood. The specific brain regions and tracts (and their interactions) that explain the heterogeneity of cognitive decline with AD are not clear. By integrating brain‐wide immunohistochemistry and cognitive outcomes we can achieve unbiased detection of regions of interest (ROIs) and identify cellular correlates of cognitive resilience for causal testing.MethodImmunohistochemistry(IHC) was completed to evaluate neurodegeneration (NeuN), gliosis (Iba1&GFAP), amyloid beta(Aβ) pathology(AB1‐42), and cell bodies(Thionine) in adult (6 months(m)) and middle‐aged (14m) mice of the AD‐BXD genetic reference panel (n = 227). Using the QUINT workflow, hemibrain slices were systematically segmented and registered to the Allen Brain Atlas to gain a global perspective of percent cell and pathology coverage. IHC traits were correlated with contextual fear conditioning outcomes to identify regions whose stain composition is associated with memory performance.ResultsContrary to our prior work using ELISA‐based Aβ measurement, we find that Aβ quantified via IHC at the presymptomatic time point (6m) is strongly correlated with differences in short‐ and long‐term memory in 14m female 5XFAD carriers. Furthermore, the degree of astrogliosis at 6m in cortical, striatal, and thalamic regions acts as a predictor of cognitive outcomes at 14m. While age‐related decreases in NeuN load were not observed, wide variation in neurodegeneration levels could be attributed to strain differences and 14m NeuN load was positively correlated with 14m long‐term memory among this female 5XFAD population. Highlighting the importance of genetic background on AD progression, we were able to categorize strains as resilient or susceptible to pathological and cognitive decline and evaluate the overlap of these traits. Strains that exhibit the unique identity of being pathologically susceptible but cognitively resilient offer a novel opportunity to investigate the underlying mechanisms of protection from cognitive decline with AD.ConclusionIntegrating brain‐wide IHC and behavioral data, we were able to identify regional and cellular correlates that may predict downstream cognitive outcomes. Detection of these biomarkers may prove a valuable resource to disseminate the insidious prodromal stages of AD in which biochemical changes precede apparent clinical symptoms.

21 Assessment of Semantic Memory Decline in aMCI : Naming and Semantic Knowledge of Unique and Non-Unique Entities

Objective:Semantic memory deficits have been reported in both Alzheimer's disease (AD) and amnestic mild cognitive impairment (aMCI). However, the nature of this decline is still a matter of debate. The aim of this study was to explore the patterns of semantic memory impairment in aMCI by examining performance on naming tasks, and on tests assessing both general and specific semantic knowledge.Participants and Methods:Participants were divided in two groups matched for age and education, one comprising 33 aMCI individuals and the other 39 healthy controls. Three experimental tests assessing naming and semantic knowledge of unique items of famous persons (FACE) and places (PLACE), logos recognition (LOGO: brands and pictograms), and non-unique entities (Boston Naming Test: BNT) were administered, and the performance of the two groups was compared.Results:Lower scores were observed on all naming tests (PLACE, FACE, LOGO and BNT) in the aMCI group compared to controls. On the PLACE test, the general knowledge mean score (M=84.5, SD=12.9) was significantly higher than the specific knowledge mean score (M=54.2, SD=18.5) in aMCI participants (t(31)=11.9, p<.001), but not in controls (general: M=92.2, SD=11.1; specific: M=73.7, SD=15.8), and there was a significant Group X Type of knowledge interaction (F(1,1)=15.13, p <.001, n2 = 18). On the FACE test, in addition to significant group and condition (naming, semantic questions) main effects, a significant interaction was found (F(1,1)=7.19, p = .009, n2 = .09). On the LOGO task, controls were significantly better on brand items (M= 94.4, SD=10.5) than on pictograms (M=83.3, SD=12.2), while no significant difference was noted in aMCI (brands: M=81.5, SD=22.6; pictograms: M=77.5, SD=14.1). Lastly, on the BNT, aMCI participants benefited more from phonemic cues than controls (F(1,1)=16.56, p<.001, n2=19), suggesting a lexical access deficit, in addition to their semantic memory impairment.Conclusions:This study adds to the growing evidence confirming the presence of semantic memory deficits in aMCI. Specific semantic knowledge seems to be more affected than general semantic knowledge, a finding reported in previous studies. Lexical access deficits, in addition to semantic decline, were also observed in the aMCI group. These results allow for a better understanding of the pattern of semantic memory deficits in the prodromal stage of AD and could potentially facilitate diagnosis of aMCI.

Multipredictor risk models for predicting individual risk of Alzheimer’s disease

BackgroundEarly prevention of Alzheimer’s disease (AD) is a feasible way to delay AD onset and progression. Information on AD prediction at the individual patient level will be useful in AD prevention. In this study, we aim to develop risk models for predicting AD onset at individual level using optimal set of predictors from multiple features.MethodsA total of 487 cognitively normal (CN) individuals and 796 mild cognitive impairment (MCI) patients were included from Alzheimer's Disease Neuroimaging Initiative. All the participants were assessed for clinical, cognitive, magnetic resonance imaging and cerebrospinal fluid (CSF) markers and followed for mean periods of 5.6 years for CN individuals and 4.6 years for MCI patients to ascertain progression from CN to incident prodromal stage of AD or from MCI to AD dementia. Least Absolute Shrinkage and Selection Operator Cox regression was applied for predictors selection and model construction.ResultsDuring the follow-up periods, 139 CN participants had progressed to prodromal AD (CDR ≥ 0.5) and 321 MCI patients had progressed to AD dementia. In the prediction of individual risk of incident prodromal stage of AD in CN individuals, the AUC of the final CN model was 0.81 within 5 years. The final MCI model predicted individual risk of AD dementia in MCI patients with an AUC of 0.92 within 5 years. The models were also associated with longitudinal change of Mini-Mental State Examination (p < 0.001 for CN and MCI models). An Alzheimer’s continuum model was developed which could predict the Alzheimer’s continuum for individuals with normal AD biomarkers within 3 years with high accuracy (AUC = 0.91).ConclusionsThe risk models were able to provide personalized risk for AD onset at each year after evaluation. The models may be useful for better prevention of AD.

Detecting Anosognosia from the Prodromal Stage of Alzheimer's Disease.

Though not originally developed for this purpose, the Healthy Aging Brain Care Monitor (HABC-M) seems a valuable instrument for assessing anosognosia in Alzheimer's disease (AD). Our study aimed at 1) investigating the validity of the HABC-M (31 items), and its cognitive, psychological, and functional subscales, in discriminating AD patients from controls; 2) exploring whether the HABC-M discrepancy scores between the self-reports of patients/controls in these different domains and the respective ratings provided by their caregivers/informants correlate with an online measure of self-awareness; 3) determining whether the caregiver burden level, also derived from the HABC-M, could add additional support for detecting anosognosia. The HABC-M was administered to 30 AD patients and 30 healthy controls, and to their caregivers/informants. A measure of online awareness was established from subjects' estimation of their performances in a computerized experiment. The HABC-M discrepancy scores distinguished AD patients from controls. The cognitive subscale discriminated the two groups from the prodromal AD stage, with an AUC of 0.88 [95% CI: 0.78;0.97]. Adding the caregiver burden level raised it to 0.94 [0.86;0.99]. Significant correlations between the HABC-M and online discrepancy scores were observed in the patients group, providing convergent validity of these methods. The cognitive HABC-M (six items) can detect anosognosia across the AD spectrum. The caregiver burden (four items) may corroborate the suspicion of anosognosia. The short-hybrid scale, built from these 10 items instead of the usual 31, showed the highest sensitivity for detecting anosognosia from the prodromal AD stage, which may further help with timely diagnosis.

The "when" matters: Evidence from memory markers in the clinical continuum of Alzheimer's disease.

Cognitive assessment able to detect impairments in the early neuropathological stages of Alzheimer's disease (AD) is urgently needed. The visual short-term memory binding task (VSTMBT) and the Free and Cued Selective Reminding Test (FCSRT) have been recommended by the neurodegenerative disease working group as promising tests to aid in the early detection of AD. In this study, we investigated their complementary value across the clinical stages of the AD continuum. One hundred and seventeen older adults with subjective cognitive complaint (SCC), 79 with mild cognitive impairment (MCI), 31 patients with AD dementia (ADD), and 37 cognitively unimpaired (CU) subjects, underwent assessment with the VSTMBT and the picture version of the Spanish FCSRT. After controlling for multiple comparisons, significant differences were found across groups. The VSTMBT was the only test that "marginally" differentiated between CU and SCC (d = 0.47, p = .052). Moreover, whereas the FCSRT showed a gradient (CU = SCC) > MCI > ADD, the VSTMBT gradient was CU > SCC > (MCI = ADD) suggesting that conjunctive binding deficits assessed by the latter may be sensitive to the very early stages of the disease. Our results suggest that the VSTMBT and the FCSRT are sensitive to the clinical continuum of AD. Whereas the former detects changes in the early prodromal stages, the latter is more sensitive to the advanced prodromal stages of AD. These novel tests can aid in the early detection, monitor disease progression and response to treatment, and thus support drug development programs. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Impact of transcranial direct current stimulation on white matter microstructure integrity in mild cognitive impairment patients according to effect modifiers as risk factors for Alzheimer's disease.

Little research exists on how individual risk factors for Alzheimer's disease (AD) affect the intermediate phenotype after transcranial direct current stimulation (tDCS), despite the importance of precision medicine-based therapeutic approaches. To determine how an application of sequential tDCS (2 mA/day, left dorsolateral prefrontal cortex, 10 sessions) affects changes in white matter (WM) microstructure integrity in 63 mild cognitive impairment (MCI) patients with effect modifiers such as Aβ deposition, APOE ε4 carrier status, BDNF Val66Met polymorphism status, and sex. We examined individual effect modifier-by-tDCS interactions and multiple effect modifiers-by-tDCS interactions for diffusion metrics. We also evaluated the association between baseline Aβ deposition and changes in WM microstructure integrity following tDCS. We found that APOE ε4 carrier status and sex had a significant interaction with tDCS, resulting in increased fractional anisotropy (FA) in the right uncinate fasciculus (UF) after stimulation. Additionally, we observed multiple effect modifiers-by-tDCS interactions on WM integrity of the right UF, leading to a more pronounced increase in FA values in APOE ε4 carriers and females with Val66 homozygotes. Finally, baseline Aβ deposition was positively associated with a difference in FA of the left cingulum in the hippocampal area, which showed a positive association with the changes in the score for delayed memory. Our study shows the differential impact of individual AD risk factors on changes in the early intermediate phenotype after sequential tDCS in MCI patients. This research emphasizes the importance of precision medicine approaches in tDCS for the prodromal stages of AD.

AT(N) biomarker profiles and Alzheimer's disease symptomology in Down syndrome.

Down syndrome (DS) is a genetic cause of early-onset Alzheimer's disease (AD). The National Institute on Aging-Alzheimer's Association AT(N) Research Framework is a staging model for AD biomarkers but has not been assessed in DS. Data are from the Alzheimer's Biomarker Consortium-Down Syndrome. Positron emission tomography (PET) amyloid beta (Aβ; 15 mCi of [11 C]Pittsburgh compound B) and tau (10 mCi of [18 F]AV-1451) were used to classify amyloid (A) -/+ and tau (T) +/-. Hippocampal volume classified neurodegeneration (N) -/+. The modified Cued Recall Test assessed episodic memory. Analyses included 162 adults with DS (aged M=38.84 years, standard deviation=8.41). Overall, 69.8% of participants were classified as A-/T-/(N)-, 11.1% were A+/T-/(N)-, 5.6% were A+/T+/(N)-, and 9.3% were A+/T+/(N)+. Participants deemed cognitively stable were most likely to be A-T-(N)- and A+T-(N)-. Tau PET (T+) most closely aligning with memory impairment and AD clinical status. Findings add to understanding of AT(N) biomarker profiles in DS. Overall, 69.8% of adults with Down syndrome (DS) aged 25 to 61 years were classified as amyloid (A)-/tau (T)-/neurodegeneration (N)-, 11.1% were A+/T-/(N)-, 5.6% were A+/T+/(N)-, and 9.3% were A+/T+/(N)+. The AT(N) profiles were associated with clinical Alzheimer's disease (AD) status and with memory performance, with the presence of T+ aligned with AD clinical symptomology. Findings inform models for predicting the transition to the prodromal stage of AD in DS.

The effect of plasma cortisol on hippocampal atrophy and clinical progression in mild cognitive impairment.

Both elevated cortisol and hippocampal volume have been linked to an increased risk for the development of Alzheimer's disease (AD). This longitudinal study assessed the effects of plasma cortisol on hippocampal atrophy and clinical progression rates in patients with mild cognitive impairment (MCI). Patients with amnestic MCI (n=304) were selected from the Alzheimer's Disease Neuroimaging Initiative (ADNI) based on availability of baseline plasma cortisol and hippocampal volume measures, assessed at baseline and during follow-ups. We investigated associations between plasma cortisol, hippocampal volume, and risk of clinical progression to AD over a study period of up to 100 months (mean follow-up time 36.8 months) using linear mixed models, Cox proportional hazards models, and Kaplan-Meier estimators. Plasma cortisol predicted greater hippocampal atrophy, such that participants with higher cortisol showed faster decline in hippocampal volume over time (interaction: β=-0.15, p=0.004). Small hippocampal volume predicted a higher risk of clinical progression to AD (haard ratio [HR]=2.15; confidence in terval [CI], 1.64-2.80; p<0.001). A similar effect was not found for cortisol (HR=1.206; CI, 0.82-1.37; p=0.670) and there was no statistical evidence for an interaction between hippocampal volume and cortisol on clinical progression (HR=0.81; CI, 0.57-0.17; p=0.260). Our findings suggest that higher cortisol predicts higher hippocampal atrophy, which in turn is a risk factor for progression to AD. Regulation of the hypothalamic-pituitary-adrenal axis through stress-reducing lifestyle interventions might be a protective factor against hippocampal degeneration at the prodromal stage of AD.

Olfactory memory in mild cognitive impairment and Alzheimer's disease.

Olfaction is impaired in Alzheimer's disease (AD). However, olfactory memory has rarely been examined. As the pathogenesis of AD remains largely unknown, collecting more data regarding the occurrence and progression of its symptoms would help gain more insight into the disease. To investigate olfactory memory and its relationship with verbal memory and other clinical features in patients with early-stage AD. Three groups of participants were enrolled in this study: patients with mild dementia due to AD (MD-AD, N = 30), patients with mild cognitive impairment due to AD (MCI-AD, N = 30), and cognitively normal older participants (CN, N = 30). All participants underwent cognitive evaluation (Clinical Dementia Rating scale, Mini Mental State Examination, Alzheimer's Disease Assessment Scale-Cognitive Subscale, delayed verbal recall, and verbal fluency tests) and assessment of olfactory immediate and delayed recognition memory. Olfactory immediate and delayed recognition memory scores were significantly lower in the MD-AD group than in the MCI-AD and CN groups. The MCI-AD and CN groups did not differ significantly [in both cases, Kruskal-Wallis test, p < 0.05; post hoc analysis revealed significant differences between the MD-AD and MCI-AD groups and between the MD-AD and CN groups (p < 0.05), and no significant difference between the MCI-AD and CN groups (p > 0.05)]. Verbal immediate recall, delayed recall after 5 min, and delayed recall after 30 min scores were significantly worse in the MD-AD and MCI-AD groups than in the CN group. MD-AD and MCI-AD groups did not differ significantly [in all cases Kruskal-Wallis test, p < 0.05; post hoc analysis revealed significant differences between MD-AD and CN groups, and MCI-AD and CN groups (p < 0.05) and no significant difference between MD-AD and MCI-AD groups (p > 0.05)]. Duration of AD symptoms was a strong predictor of both immediate and delayed olfactory recognition memory scores. Olfactory memory impairment was observed in patients with AD. The changes progress during the course of the disease. However, unlike verbal memory, olfactory memory is not significantly impaired in the prodromal stage of AD.

APOEε4 genotype boosts neurodegenerative structural changes in medial temporal lobe areas in adults with Mild Cognitive Impairment

AbstractBackgroundApolipoprotein E ε4 allele (APOEε4) is considered the major genetic risk factor of Alzheimer´s Disease (AD). Structural magnetic resonance imaging (sMRI) studies demonstrated that, compared to APOEε4 non‐carriers, APOEε4 carriers display structural changes in lateral and medial temporal lobe (MTL). However, the knowledge about the impact of this genotype on hippocampal subfields is still limited. The present sMRI study aimed to evaluate volumetric and cortical thickness differences between adults with mild cognitive impairment (MCI) APOEε4 non‐carriers compared with MCI‐APOEε4 carriers.MethodTwelve MCI‐APOEε4 non‐carriers (mean age: 70.33 years, SD: 5.12) and ten MCI‐APOEε4 carriers (mean age: 72.70 years, SD: 6.38), diagnosed as MCI according Petersen criteria (Petersen, 2004; Albert et al., 2011), underwent neuropsychological assessment, cerebrospinal fluid, genetic and MRI examinations. MRI surface‐based morphometry analyses was conducted with the FreeSurfer software to evaluate volumetric and thickness differences in the hippocampal subfields and its surrounding MTL areas.ResultCompared with MCI‐APOEε4 non‐carriers, the MCI‐APOEε4 carriers group showed a significant reduced volume in several areas of the left hemisphere. Specifically, in this hemisphere volumetric changes were found in the entorhinal cortex, the whole hippocampus and in its head, body and tail; the head of presubiculum, the head and body of subiculum, the CA1, CA3, CA4 subfields, the granulate cell of the molecular layer of dentate gyrus and the molecular layer of the hippocampus. This group also displayed a significant reduced volume in the right body of CA3 subfield.ConclusionThese results suggest that, in MCI adults, the presence of the APOEε4 genotype may have an additional neuropathological impact on the structure of brain regions of the MTL with a critical functional role in episodic memory, the most affected neurocognitive system in Alzheimer’s disease (AD). Particularly, the left MTL would show higher vulnerability to neurodegenerative changes in the prodromal stage of AD.