Alzheimer disease biomarkers are associated with decline in subjective memory, attention, and spatial navigation ability in clinically normal adults

OBJECTIVE

Subtle changes in memory, attention, and spatial navigation abilities have been associated with preclinical Alzheimer disease (AD). The current study examined whether baseline AD biomarkers are associated with self- and informant-reported decline in memory, attention, and spatial navigation.

METHOD

Clinically normal (Clinical Dementia Rating Scale (CDR®) = 0) adults aged 56-93 (N = 320) and their informants completed the memory, divided attention, and visuospatial abilities (which assesses spatial navigation) subsections of the Everyday Cognition Scale (ECog) annually for an average of 4 years. Biomarker data was collected within (±) 2 years of baseline (i.e., cerebrospinal fluid (CSF) p-tau181/Aβ42 ratio and hippocampal volume). Clinical progression was defined as CDR > 0 at time of final available ECog.

RESULTS

Self- and informant-reported memory, attention, and spatial navigation significantly declined over time (ps < .001). Baseline AD biomarkers were significantly associated with self- and informant-reported decline in cognitive ability (ps < .030), with the exception of p-tau181/Aβ42 ratio and self-reported attention (p = .364). Clinical progression did not significantly moderate the relationship between AD biomarkers and decline in self- or informant-reported cognitive ability (ps > .062). Post-hoc analyses indicated that biomarker burden was also associated with self- and informant-reported decline in total ECog (ps < .002), and again clinical progression did not significantly moderate these relationships (ps > .299).

CONCLUSIONS

AD biomarkers at baseline may indicate risk of decline in self- and informant-reported change in memory, attention, and spatial navigation ability. As such, subjectively reported decline in these domains may have clinical utility in tracking the subtle cognitive changes associated with the earliest stages of AD.

Utilizing Reduced Labeled Proton Clearance to Identify Preclinical Alzheimer Disease with 3D ASL MRI

Addressing the seminal pathophysiology in Alzheimer disease (AD) is the next logical focus for effective intervention, given the initial disappointing and more recent possibly encouraging results of monoclonal antibody trials. Endothelial cell dysfunction-induced blood-brain barrier leak with associated prolonged capillary mean transit time (cMTT) and glymphatic outflow dysfunction is the most proximal events in the degeneration cascade. Sensitive and reproducible markers are required to both identify early disease and assess future treatment trial outcomes. Two participants, with mild cognitive impairment (MCI) and one with AD, were evaluated clinically prior to MRI in this small case series report. From seven 3D turbo gradient and spin echo (TGSE) pulsed arterial spin echo (PASL) MRI sequences six homologous region of interest in bitemporal, bifrontal, and biparietal lobes for each sequence were examined and plotted against time. By choosing late perfusion times during cMTT phase of perfusion linear analysis of signal decay could be utilized. A reference axial FLAIR sequence was also obtained. Slope of the linear analysis correlated to the rate of labeled proton clearance with reduced clearance occurring in AD participants compared to normal participants in our previous study. Whether similar differences in clearance rate extend to either MCI or early AD was investigated. Participants were categorized by clinical phenotype before MRI and compared to previously published phenotype cohorts: n = 18 normal/healthy, n = 6 AD, n = 3 MCI. Significant differences in labeled proton clearance rates between AD and MCI/control phenotypes within bilateral temporal lobes (left p = 0.004, right p = 0.002) and within bilateral frontal lobes AD versus controls (left p = 0.001, right p = 0.008) and AD versus MCI (left p = 0.001, right p = 0.001) were found. This noninvasive MRI technique has potential for identifying MCI transition to AD.

Regional age-related atrophy after screening for preclinical alzheimer disease

Brain atrophy occurs in aging even in the absence of dementia, but it is unclear to what extent this is due to undetected preclinical Alzheimer disease. Here we examine a cross-sectional cohort (ages 18-88) free from confounding influence of preclinical Alzheimer disease, as determined by amyloid PET scans and three years of clinical evaluation post-imaging. We determine the regional strength of age-related atrophy using linear modeling of brain volumes and cortical thicknesses with age. Age-related atrophy was seen in nearly all regions, with greatest effects in the temporal lobe and subcortical regions. When modeling age with the estimated derivative of smoothed aging curves, we found that the temporal lobe declined linearly with age, subcortical regions declined faster at later ages, and frontal regions declined slower at later ages than during midlife. This age-derivative pattern was distinct from the linear measure of age-related atrophy and significantly associated with a measure of myelin. Atrophy did not detectably differ from a preclinical Alzheimer disease cohort when age ranges were matched.

Early memory deficits and extensive brain network disorganization in the AppNL-F/MAPT double knock-in mouse model of familial Alzheimer's disease

A critical challenge in current research on Alzheimer's disease (AD) is to clarify the relationship between network dysfunction and the emergence of subtle memory deficits in itspreclinical stage. The AppNL-F/MAPT double knock-in (dKI) model with humanized β-amyloid peptide (Aβ) and tau was used to investigate both memory and network dysfunctions at an early stage. Young male dKI mice (2 to 6 months) were tested in three tasks taxing different aspects of recognition memory affected in preclinical AD. An early deficit first appeared in the object-place association task at the age of 4 months, when increased levels of β-CTF and Aβ were detected in both the hippocampus and the medial temporal cortex, and tau pathology was found only in the medial temporal cortex. Object-place task-dependent c-Fos activation was then analyzed in 22 subregions across the medial prefrontal cortex, claustrum, retrosplenial cortex, and medial temporal lobe. Increased c-Fos activation was detected in the entorhinal cortex and the claustrum of dKI mice. During recall, network efficiency was reduced across cingulate regions with a major disruption of information flow through the retrosplenial cortex. Our findings suggest that early perirhinal-entorhinal pathology is associated with abnormal activity which may spread to downstream regions such as the claustrum, the medial prefrontal cortex and ultimately the key retrosplenial hub which relays information from frontal to temporal lobes. The similarity between our findings and those reported in preclinical stages of AD suggests that the AppNL-F/MAPT dKI model has a high potential for providing key insights into preclinical AD.

GPS driving: a digital biomarker for preclinical Alzheimer disease

BACKGROUND

Alzheimer disease (AD) is the most common cause of dementia. Preclinical AD is the period during which early AD brain changes are present but cognitive symptoms have not yet manifest. The presence of AD brain changes can be ascertained by molecular biomarkers obtained via imaging and lumbar puncture. However, the use of these methods is limited by cost, acceptability, and availability. The preclinical stage of AD may have a subtle functional signature, which can impact complex behaviours such as driving. The objective of the present study was to evaluate the ability of in-vehicle GPS data loggers to distinguish cognitively normal older drivers with preclinical AD from those without preclinical AD using machine learning methods.

METHODS

We followed naturalistic driving in cognitively normal older drivers for 1 year with a commercial in-vehicle GPS data logger. The cohort included n = 64 individuals with and n = 75 without preclinical AD, as determined by cerebrospinal fluid biomarkers. Four Random Forest (RF) models were trained to detect preclinical AD. RF Gini index was used to identify the strongest predictors of preclinical AD.

RESULTS

The F1 score of the RF models for identifying preclinical AD was 0.85 using APOE ε4 status and age only, 0.82 using GPS-based driving indicators only, 0.88 using age and driving indicators, and 0.91 using age, APOE ε4 status, and driving. The area under the receiver operating curve for the final model was 0.96.

CONCLUSION

The findings suggest that GPS driving may serve as an effective and accurate digital biomarker for identifying preclinical AD among older adults.

Quantification of white matter cellularity and damage in preclinical and early symptomatic Alzheimer's disease

Interest in understanding the roles of white matter (WM) inflammation and damage in the pathophysiology of Alzheimer disease (AD) has been growing significantly in recent years. However, in vivo magnetic resonance imaging (MRI) techniques for imaging inflammation are still lacking. An advanced diffusion-based MRI method, neuro-inflammation imaging (NII), has been developed to clinically image and quantify WM inflammation and damage in AD. Here, we employed NII measures in conjunction with cerebrospinal fluid (CSF) biomarker classification (for β-amyloid (Aβ) and neurodegeneration) to evaluate 200 participants in an ongoing study of memory and aging. Elevated NII-derived cellular diffusivity was observed in both preclinical and early symptomatic phases of AD, while disruption of WM integrity, as detected by decreased fractional anisotropy (FA) and increased radial diffusivity (RD), was only observed in the symptomatic phase of AD. This may suggest that WM inflammation occurs earlier than WM damage following abnormal Aβ accumulation in AD. The negative correlation between NII-derived cellular diffusivity and CSF Aβ42 level (a marker of amyloidosis) may indicate that WM inflammation is associated with increasing Aβ burden. NII-derived FA also negatively correlated with CSF t-tau level (a marker of neurodegeneration), suggesting that disruption of WM integrity is associated with increasing neurodegeneration. Our findings demonstrated the capability of NII to simultaneously image and quantify WM cellularity changes and damage in preclinical and early symptomatic AD. NII may serve as a clinically feasible imaging tool to study the individual and composite roles of WM inflammation and damage in AD.

Staging biomarkers in preclinical autosomal dominant Alzheimer's disease by estimated years to symptom onset

INTRODUCTION

Staging preclinical Alzheimer disease (AD) by the expected years to symptom onset (EYO) in autosomal dominant AD (ADAD) through biomarker correlations is important.

METHODS

We estimated the correlation matrix between EYO/cognition and imaging/CSF biomarkers, and searched for the EYO cutoff where a change in the correlations occurred before and after the cutoff among the asymptomatic mutation carriers of ADAD. We then estimated the longitudinal rate of change for biomarkers/cognition within each preclinical stage defined by the EYO.

RESULTS

Based on the change in the correlations, the preclinical ADAD was divided by EYOs -7 and -13 years. Mutation carriers demonstrated a temporal ordering of biomarker/cognition changes across the three preclinical stages.

DISCUSSION

Duration of each preclinical stage can be estimated in ADAD, facilitating better planning of prevention trials with the EYO cutoffs under the recently released FDA guidance. The generalization of these results to sporadic AD warrants further investigation.

Scores Obtained from a Simple Cognitive Test of Visuospatial Episodic Memory Performed Decades before Death Are Associated with the Ultimate Presence of Alzheimer Disease Pathology

BACKGROUND

Community- or population-based longitudinal studies of cognitive ability with a brain donation end point offer an opportunity to examine relationships between pathology and cognitive state prior to death. Discriminating the earliest signs of dementing disorders, such as Alzheimer disease (AD), is necessary to undertake early interventions and treatments.

METHODS

The neuropathological profile of brains donated from The University of Manchester Longitudinal Study of Cognition in Normal Healthy Old Age, including CERAD (Consortium to Establish a Registry for Alzheimer's Disease) and Braak stage, was assessed by immunohistochemistry. Cognitive test scores collected 20 years prior to death were correlated with the extent of AD pathology present at death.

RESULTS

Baseline scores from the Memory Circle test had the ability to distinguish between individuals who developed substantial AD pathology and those with no, or low, AD pathology. Predicted test scores at the age of 65 years also discriminated between these pathology groups. The addition of APOE genotype further improved the discriminatory ability of the model.

CONCLUSIONS

The results raise the possibility of identifying individuals at future risk of the neuropathological changes associated with AD over 20 years before death using a simple cognitive test. This work may facilitate early interventions, therapeutics and treatments for AD by identifying at-risk and minimally affected (in pathological terms) individuals.

Objective features of subjective cognitive decline in a United States national database

INTRODUCTION

Functional and cognitive features of subjective cognitive decline (SCD) were identified in a longitudinal database from the National Alzheimer's Coordinating Center.

METHODS

Cognitively normal older adults with (SCD+) and without (SCD-) self-reported memory complaints (N = 3915) were compared on (1) baseline Functional Assessment Questionnaire ratings, (2) baseline scores and longitudinal rate of change estimates from nine neuropsychological tests, and (3) final clinical diagnoses.

RESULTS

SCD+ had higher baseline ratings of functional impairment, reduced episodic memory practice effects and poorer performance on neuropsychological tests of psychomotor speed and language, and higher frequencies of mild cognitive impairment and dementia diagnoses at the end of follow-up compared with the SCD-group.

DISCUSSION

Subtle clinical features of SCD identified in this large cohort are difficult to detect at the individual level. More sensitive tests are needed to identify those with SCD who are vulnerable to cognitive decline and dementia.

Neuropsychological measures that detect early impairment and decline in preclinical Alzheimer disease

Identifying which neuropsychological measures detect early cognitive changes associated with Alzheimer disease (AD), brain pathology would be helpful clinically for the diagnosis of early AD and for the design of clinical trials. We evaluated which neuropsychological measures in our cognitive battery are most strongly associated with cerebrospinal fluid (CSF) biomarkers of AD brain pathology. We studied a large cohort (n = 233) of middle-to older-aged community-dwelling individuals (mean age 61 years) who had no clinical symptoms of dementia and underwent baseline CSF collection at baseline. Participants completed a battery of 9 neuropsychological measures at baseline and then every 1 to 3 years. CSF tau/Aβ42 was associated with baseline performance on 5/9 neuropsychological measures, especially measures of episodic memory, and longitudinal performance on 7/9 neuropsychological measures, especially measures of global cognition. The free recall portion of the Free and Cued Selective Reminding Task (FCSRT-free) detected declining cognition in the high CSF tau/Aβ42 group the earliest, followed by another measure of episodic memory and a sequencing task.

Subjective Cognitive Impairment Is a Predominantly Benign Condition in Memory Clinic Patients Followed for 6 Years: The Gothenburg-Oslo MCI Study

Background/Aims

In the quest for prevention or treatment, there is a need to find early markers for preclinical dementia. This study observed memory clinic patients with subjective cognitive impairment (SCI) and normal cognitive function at baseline. The primary aim was to address SCI as a potential risk factor for cognitive decline. The secondary aim was to address a potential relation between (1) baseline cerebrospinal fluid biomarkers and (2) a decline in memory performance over the first 2 years of follow-up, with a possible cognitive decline after 6 years.

Methods

Eighty-one patients (mean age 61 years) were recruited from university memory clinics and followed up for 6 years.

Results

Eighty-six percent of the cohort remained cognitively stable or improved, 9% developed mild cognitive impairment, and only 5% (n = 4) developed dementia. Regression analysis revealed that low levels of Aβ₄₂ at baseline and memory decline during the first 2 years predicted dementia. When combined, these variables were associated with a 50% risk of developing dementia.

Conclusions

Cognitive stability for 86% of the cohort suggests that SCI is predominantly a benign condition with regard to neuropathology. The low number of individuals who developed dementia limits the generalizability of the results and discussion of progression factors.

Medial temporal lobe subregional morphometry using high resolution MRI in Alzheimer's disease

Autopsy studies of Alzheimer's disease (AD) have found that neurofibrillary tangle (NFT) pathology of the medial temporal lobe (MTL) demonstrates selective topography with relatively stereotyped subregional involvement at early disease stages, prompting interest in more granular measurement of these structures with in vivo magnetic resonance imaging. We applied a novel, automated method for measurement of hippocampal subfields and extrahippocampal MTL cortical regions. The cohort included cognitively normal (CN) adults (n = 86), early mild cognitive impairment (n = 43), late MCI (n = 22), and mild AD (n = 40) patients from the Alzheimer's Disease Neuroimaging Initiative (ADNI). For pseudolongitudinal analysis of the continuum from preclinical to mild AD dementia, the groups were further divided according to amyloid status based on positron emission tomography. Specific subregions associated with the early NFT pathology of AD were more sensitive to preclinical and early prodromal AD than whole hippocampal volume while more diffuse involvement was found in later stages. In particular, BA35, the first region associated with NFT deposition, was the only region to discriminate preclinical AD from amyloid negative cognitively normal adults ("normal aging"). In general, patterns of atrophy in the pseudolongitudinal analysis largely recapitulated Braak staging of NFTs within the MTL.