Objective subtle cognitive difficulties predict future amyloid accumulation and neurodegeneration

Comorbid neuropathology and atypical presentation of Alzheimer's disease

INTRODUCTION

Alzheimer's disease (AD) neuropathological changes present with amnestic and nonamnestic (atypical) syndromes. The contribution of comorbid neuropathology as a substratum of atypical expression of AD remains under investigated.

METHODS

We examined whether atypical AD exhibited increased comorbid neuropathology compared to typical AD and if such neuropathologies contributed to the accelerated clinical decline in atypical AD.

RESULTS

We examined 60 atypical and 101 typical AD clinicopathological cases. The number of comorbid pathologies was similar between the groups (p = 0.09). Argyrophilic grain disease was associated with atypical presentation (p = 0.008) after accounting for sex, age of onset, and disease duration. Vascular brain injury was more common in typical AD (p = 0.022). Atypical cases had a steeper Mini-Mental Status Examination (MMSE) decline over time (p = 0.033).

DISCUSSION

Comorbid neuropathological changes are unlikely to contribute to atypical AD presentation and the steeper cognitive decline seen in this cohort.

Highlights

Autopsy cohort of 60 atypical and 101 typical AD; does comorbid pathology explain atypical presentation?Atypical versus Typical AD: No significant differences in comorbid neuropathologies were found (p = 0.09).Argyrophilic Grain Disease Association: significantly correlates with atypical AD presentations, suggesting a unique neuropathological pattern (p = 0.008).Vascular Brain Injury Prevalence: Vascular brain injury is more common in typical AD than in atypical AD (p = 0.022).Cognitive Decline in Atypical AD: Atypical AD patients experience a steeper cognitive decline measured by MMSE than those with typical AD despite lacking more comorbid neuropathology, highlighting the severity of atypical AD pathogenesis (p = 0.033).

Process approach as a cognitive biomarker related to gray matter volume in mild cognitive impairment and Alzheimer's disease

BACKGROUND

Process approach is valuable for memory assessment in Alzheimer's disease (AD) and mild cognitive impairment (MCI), yet its underlying mechanisms remain elusive. This study aims to synergize the process approach with brain structure analysis to explore both the discriminative capacity and potential mechanisms underlying the process approach.

METHODS

37 subjects of MCI, 35 subjects of AD and 38 subjects of healthy control (HC) were included. The process approach in Auditory Verbal Learning Test (AVLT), including discriminability (A'), response bias (B"D), semantic clustering (LBCsem) and serial clustering (LBCser) was performed. The gray matter volume (GMV) was analyzed by voxel-based morphometry. Receiver operating characteristic (ROC) analysis and partial correlations were conducted to explore the value of the process approach and investigate the relationship between the process approach, traditional indices of AVLT and GMV.

RESULTS

ROC analysis showed the value of A', B"D and LBCser in differentiating MCI and AD. Combining AVLT-Immediately Recall (AVLT-IR) and LBCser showed a higher value in diagnosing MCI. Partial correlations revealed that in the MCI group, A' and B"D were mainly positively associated with GMV of the hippocampus and temporal lobe.

CONCLUSION

This study indicated that the process approach is a promising cognitive biomarker to detect MCI and AD.

Impact of amyloid and tau positivity on longitudinal brain atrophy in cognitively normal individuals

BACKGROUND

Individuals on the preclinical Alzheimer's continuum, particularly those with both amyloid and tau positivity (A + T +), display a rapid cognitive decline and elevated disease progression risk. However, limited studies exist on brain atrophy trajectories within this continuum over extended periods.

METHODS

This study involved 367 ADNI participants grouped based on combinations of amyloid and tau statuses determined through cerebrospinal fluid tests. Using longitudinal MRI scans, brain atrophy was determined according to the whole brain, lateral ventricle, and hippocampal volumes and cortical thickness in AD-signature regions. Cognitive performance was evaluated with the Preclinical Alzheimer's Cognitive Composite (PACC). A generalized linear mixed-effects model was used to examine group × time interactions for these measures. In addition, progression risks to mild cognitive impairment (MCI) or dementia were compared among the groups using Cox proportional hazards models.

RESULTS

A total of 367 participants (48 A + T + , 86 A + T - , 63 A - T + , and 170 A - T - ; mean age 73.8 years, mean follow-up 5.1 years, and 47.4% men) were included. For the lateral ventricle and PACC score, the A + T - and A + T + groups demonstrated statistically significantly greater volume expansion and cognitive decline over time than the A - T - group (lateral ventricle: β = 0.757 cm3/year [95% confidence interval 0.463 to 1.050], P < .001 for A + T - , and β = 0.889 cm3/year [0.523 to 1.255], P < .001 for A + T + ; PACC: β =  - 0.19 /year [- 0.36 to - 0.02], P = .029 for A + T - , and β =  - 0.59 /year [- 0.80 to - 0.37], P < .001 for A + T +). Notably, the A + T + group exhibited additional brain atrophy including the whole brain (β =  - 2.782 cm3/year [- 4.060 to - 1.504], P < .001), hippocampus (β =  - 0.057 cm3/year [- 0.085 to - 0.029], P < .001), and AD-signature regions (β =  - 0.02 mm/year [- 0.03 to - 0.01], P < .001). Cox proportional hazards models suggested an increased risk of progressing to MCI or dementia in the A + T + group versus the A - T - group (adjusted hazard ratio = 3.35 [1.76 to 6.39]).

CONCLUSIONS

In cognitively normal individuals, A + T + compounds brain atrophy and cognitive deterioration, amplifying the likelihood of disease progression. Therapeutic interventions targeting A + T + individuals could be pivotal in curbing brain atrophy, cognitive decline, and disease progression.

Sensitivity of the African neuropsychology battery memory subtests and learning slopes in discriminating APOE 4 and amyloid pathology in adult individuals in the Democratic Republic of Congo

Background

The current study examined the sensitivity of two memory subtests and their corresponding learning slope metrics derived from the African Neuropsychology Battery (ANB) to detect amyloid pathology and APOEε4 status in adults from Kinshasa, the Democratic Republic of the Congo.

Methods

85 participants were classified for the presence of β-amyloid pathology and based on allelic presence of APOEε4 using Simoa. All participants were screened using CSID and AQ, underwent verbal and visuospatial memory testing from ANB, and provided blood samples for plasma Aβ42, Aβ40, and APOE proteotype. Pearson correlation, linear and logistic regression were conducted to compare amyloid pathology and APOEε4 status with derived learning scores, including initial learning, raw learning score, learning over trials, and learning ratio.

Results

Our sample included 35 amyloid positive and 44 amyloid negative individuals as well as 42 without and 39 with APOEε4. All ROC AUC ranges for the prediction of amyloid pathology based on learning scores were low, ranging between 0.56-0.70 (95% CI ranging from 0.44-0.82). The sensitivity of all the scores ranged between 54.3-88.6, with some learning metrics demonstrating good sensitivity. Regarding APOEε4 prediction, all AUC values ranged between 0.60-0.69, with all sensitivity measures ranging between 53.8-89.7. There were minimal differences in the AUC values across learning slope metrics, largely due to the lack of ceiling effects in this sample.

Discussion

This study demonstrates that some ANB memory subtests and learning slope metrics can discriminate those that are normal from those with amyloid pathology and those with and without APOEε4, consistent with findings reported in Western populations.

Alteration of functional connectivity network in population of objectively-defined subtle cognitive decline

The objectively-defined subtle cognitive decline individuals had higher progression rates of cognitive decline and pathological deposition than healthy elderly, indicating a higher risk of progressing to Alzheimer's disease. However, little is known about the brain functional alterations during this stage. Thus, we aimed to investigate the functional network patterns in objectively-defined subtle cognitive decline cohort. Forty-two cognitive normal, 29 objectively-defined subtle cognitive decline and 55 mild cognitive impairment subjects were included based on neuropsychological measures from the Alzheimer's disease Neuroimaging Initiative dataset. Thirty cognitive normal, 22 objectively-defined subtle cognitive declines and 48 mild cognitive impairment had longitudinal MRI data. The degree centrality and eigenvector centrality for each participant were calculated by using resting-state functional MRI. For cross-sectional data, analysis of covariance was performed to detect between-group differences in degree centrality and eigenvector centrality after controlling age, sex and education. For longitudinal data, repeated measurement analysis of covariance was used for comparing the alterations during follow-up period among three groups. In order to classify the clinical significance, we correlated degree centrality and eigenvector centrality values to Alzheimer's disease biomarkers and cognitive function. The results of analysis of covariance showed significant between-group differences in eigenvector centrality and degree centrality in left superior temporal gyrus and left precuneus, respectively. Across groups, the eigenvector centrality value of left superior temporal gyrus was positively related to recognition scores in auditory verbal learning test, whereas the degree centrality value of left precuneus was positively associated with mini-mental state examination total score. For longitudinal data, the results of repeated measurement analysis of covariance indicated objectively-defined subtle cognitive decline group had the highest declined rate of both eigenvector centrality and degree centrality values than other groups. Our study showed an increased brain functional connectivity in objectively-defined subtle cognitive decline individuals at both local and global level, which were associated with Alzheimer's disease pathology and neuropsychological assessment. Moreover, we also observed a faster declined rate of functional network matrix in objectively-defined subtle cognitive decline individuals during the follow-ups.

Consensus on rapid screening for prodromal Alzheimer's disease in China

Alzheimer's disease (AD) is a common cause of dementia, characterised by cerebral amyloid-β deposition, pathological tau and neurodegeneration. The prodromal stage of AD (pAD) refers to patients with mild cognitive impairment (MCI) and evidence of AD's pathology. At this stage, disease-modifying interventions should be used to prevent the progression to dementia. Given the inherent heterogeneity of MCI, more specific biomarkers are needed to elucidate the underlying AD's pathology. Although the uses of cerebrospinal fluid and positron emission tomography are widely accepted methods for detecting AD's pathology, their clinical applications are limited by their high costs and invasiveness, particularly in low-income areas in China. Therefore, to improve the early detection of Alzheimer's disease (AD) pathology through cost-effective screening methods, a panel of 45 neurologists, psychiatrists and gerontologists was invited to establish a formal consensus on the screening of pAD in China. The supportive evidence and grades of recommendations are based on a systematic literature review and focus group discussion. National meetings were held to allow participants to review, vote and provide their expert opinions to reach a consensus. A majority (two-thirds) decision was used for questions for which consensus could not be reached. Recommended screening methods are presented in this publication, including neuropsychological assessment, peripheral biomarkers and brain imaging. In addition, a general workflow for screening pAD in China is established, which will help clinicians identify individuals at high risk and determine therapeutic targets.

Symptomatic Clusters Related to Amyloid Positivity in Cognitively Unimpaired Individuals

Background

The NIA-AA Research Framework on Alzheimer's disease (AD) proposes a transitional stage (stage 2) characterized by subtle cognitive decline, subjective cognitive decline (SCD) and mild neurobehavioral symptoms (NPS).

Objective

To identify participant clusters based on stage 2 features and assess their association with amyloid positivity in cognitively unimpaired individuals.

Methods

We included baseline data of N = 338 cognitively unimpaired participants from the DELCODE cohort with data on cerebrospinal fluid biomarkers for AD. Classification into the AD continuum (i.e., amyloid positivity, A+) was based on Aβ42/40 status. Neuropsychological test data were used to assess subtle objective cognitive dysfunction (OBJ), the subjective cognitive decline interview (SCD-I) was used to detect SCD, and the Neuropsychiatric Inventory Questionnaire (NPI-Q) was used to assess NPS. A two-step cluster analysis was carried out and differences in AD biomarkers between clusters were analyzed.

Results

We identified three distinct participant clusters based on presented symptoms. The highest rate of A+ participants (47.6%) was found in a cluster characterized by both OBJ and SCD. A cluster of participants that presented with SCD and NPS (A+:26.6%) and a cluster of participants with overall few symptoms (A+:19.7%) showed amyloid positivity in a range that was not higher than the expected A+ rate for the age group. Across the full sample, participants with a combination of SCD and OBJ in the memory domain showed a lower Aβ42/ptau181 ratio compared to those with neither SCD nor OBJ.

Conclusions

The cluster characterized by participants with OBJ and concomitant SCD was enriched for amyloid pathology.

Machine Learning Predicts Conversion from Normal Aging to Mild Cognitive Impairment Using Medical History, APOE Genotype, and Neuropsychological Assessment

Background

Identifying individuals at risk for mild cognitive impairment (MCI) is of urgent clinical need.

Objective

This study aimed to determine whether machine learning approaches could harness longitudinal neuropsychology measures, medical data, and APOEɛ4 genotype to identify individuals at risk of MCI 1 to 2 years prior to diagnosis.

Methods

Data from 676 individuals who participated in the 'APOE in the Predisposition to, Protection from and Prevention of Alzheimer's Disease' longitudinal study (N = 66 who converted to MCI) were utilized in supervised machine learning algorithms to predict conversion to MCI.

Results

A random forest algorithm predicted conversion 1-2 years prior to diagnosis with 97% accuracy (p = 0.0026). The global minima (each individual's lowest score) of memory measures from the 'Rey Auditory Verbal Learning Test' and the 'Selective Reminding Test' were the strongest predictors.

Conclusions

This study demonstrates the feasibility of using machine learning to identify individuals likely to convert from normal cognition to MCI.

Rey Auditory Verbal Learning Test in idiopathic normal pressure hydrocephalus and Alzheimer's disease

Objective: This study aims to evaluate the ability of the Rey Auditory Verbal Learning Test (RAVLT), to separate the early stages of idiopathic normal pressure hydrocephalus (iNPH) from Alzheimer's disease (AD), both in comparison to each other and to healthy individuals (HI). Method: The RAVLT performance regarding learning, recall and recognition, was analyzed in three matched samples comprising 30 HI, 84 participants with AD and 84 with iNPH. The clinical samples were divided into two subgroups based on scores on the MMSE, High performers (27-30 points, n = 30) and Medium performers (18-26 points, n = 54). Results: Memory performance was significantly impaired in both clinical samples relative to HI, even in the comparisons with the subgroups consisting of only High-MMSE performers. Despite similar results on measures capturing learning, the iNPH patients outperformed AD patients on measures of recall and recognition. Conclusions: Learning impairment occurs early in iNPH and AD alike, when MMSE performance is still within normal limits. RAVLT measures of delayed recall and recognition are less affected in iNPH than in AD and may serve as differential diagnostic neuropsychological markers.

Degeneration of cholinergic white matter pathways and nucleus basalis of Meynert in individuals with objective subtle cognitive impairment

We evaluated alterations in the nucleus basalis of Meynert (NBM) volume and integrity of cholinergic white matter pathways in objective subtle cognitive impairment (Obj-SCI) individuals. NBM segmentation and cholinergic pathways tracking were conducted at baseline, 12-, 24-, and 48-month follow-ups in 41 Obj-SCI individuals and 61 healthy controls (HC). The baseline and 4-year rate of change in NBM volume and cholinergic pathways mean diffusivity were compared. Associations between cholinergic index changes and pathological processes and cognitive performance were evaluated. After controlling for age, sex, APOE genotype, and total intracranial volume, Obj-SCI individuals exhibited reduced NBM volume and increased medial pathway mean diffusivity compared to HC at baseline. Furthermore, amyloid-positive Obj-SCI individuals exhibited a steeper longitudinal decline in NBM volume than HC. Additionally, decreases in NBM volume and cholinergic pathways integrity were associated with amyloid and vascular pathologies and cognitive decline. Overall, degeneration of the cholinergic system plays an important role in cognitive impairment during the preclinical stage of Alzheimer's disease, which may provide a significant target for early therapeutic interventions.

Relevance of Minor Neuropsychological Deficits in Patients With Subjective Cognitive Decline

BACKGROUND AND OBJECTIVES

To determine the relevance of minor neuropsychological deficits (MNPD) in patients with subjective cognitive decline (SCD) with regard to CSF levels of Alzheimer disease (AD) biomarkers, cognitive decline, and clinical progression to mild cognitive impairment (MCI).

METHODS

This study included patients with clinical SCD and SCD-free, healthy control (HC) participants with available baseline CSF and/or longitudinal cognitive data from the observational DZNE Longitudinal Cognitive Impairment and Dementia study. We defined MNPD as a performance of at least 0.5SD below the mean on a demographically adjusted total score derived from the Consortium to Establish a Registry for Alzheimer's Disease neuropsychological assessment battery. We compared SCD patients with MNPD and those without MNPD with regard to CSF amyloid-β (Aβ)42/Aβ40, phosphorylated tau (p-tau181), total tau and Aβ42/p-tau181 levels, longitudinal cognitive composite trajectories, and risk of clinical progression to incident MCI (follow-up M ± SD: 40.6 ± 23.7 months). In addition, we explored group differences between SCD and HC in those without MNPD.

RESULTS

In our sample (N = 672, mean age: 70.7 ± 5.9 years, 50% female), SCD patients with MNPD (n = 55, 12.5% of SCD group) showed significantly more abnormal CSF biomarker levels, increased cognitive decline, and a higher risk of progression to incident MCI (HR: 4.07, 95% CI 2.46-6.74) compared with SCD patients without MNPD (n = 384). MNPD had a positive predictive value of 57.0% (95% CI 38.5-75.4) and a negative predictive value of 86.0% (95% CI 81.9-90.1) for the progression of SCD to MCI within 3 years. SCD patients without MNPD showed increased cognitive decline and a higher risk of incident MCI compared with HC participants without MNPD (n = 215; HR: 4.09, 95% CI 2.07-8.09), while AD biomarker levels did not differ significantly between these groups.

DISCUSSION

Our results suggest that MNPD are a risk factor for AD-related clinical progression in cognitively normal patients seeking medical counseling because of SCD. As such, the assessment of MNPD could be useful for individual clinical prediction and for AD risk stratification in clinical trials. However, SCD remains a risk factor for future cognitive decline even in the absence of MNPD.

Learning slopes in early-onset Alzheimer's disease

OBJECTIVE

Investigation of learning slopes in early-onset dementias has been limited. The current study aimed to highlight the sensitivity of learning slopes to discriminate disease severity in cognitively normal participants and those diagnosed with early-onset dementia with and without β-amyloid positivity METHOD: Data from 310 participants in the Longitudinal Early-Onset Alzheimer's Disease Study (aged 41 to 65) were used to calculate learning slope metrics. Learning slopes among diagnostic groups were compared, and the relationships of slopes with standard memory measures were determined RESULTS: Worse learning slopes were associated with more severe disease states, even after controlling for demographics, total learning, and cognitive severity. A particular metric-the learning ratio (LR)-outperformed other learning slope calculations across analyses CONCLUSIONS: Learning slopes appear to be sensitive to early-onset dementias, even when controlling for the effect of total learning and cognitive severity. The LR may be the learning measure of choice for such analyses.

HIGHLIGHTS

Learning is impaired in amyloid-positive EOAD, beyond cognitive severity scores alone. Amyloid-positive EOAD participants perform worse on learning slopes than amyloid-negative participants. Learning ratio appears to be the learning metric of choice for EOAD participants.

AMES: An Automated Self-Administered Scale to Detect Incipient Cognitive Decline in Primary Care Settings

Early identification and intervention of cognitive decline could be effective to prevent progression to dementia. We developed a self-delivered cognitive screening tool, Automated Memory and Executive Screening (AMES), to assess cognitive domains including memory, language, and executive function. 189 participants with diagnoses of mild cognitive impairment (MCI, n = 43), subjective cognitive decline (SCD, n = 29), objectively-defined subtle cognitive decline (obj-SCD, n = 18), and normal controls (NC, n = 99) completed the study. AMES had good convergent validity with conventional scales, and was good to discriminate patients with MCI (area under the curve [AUC] = 0.88; sensitivity = 86%; specificity = 80%) and obj-SCD (AUC = 0.78; sensitivity = 89%; specificity = 63%) from NC. These findings support that AMES is an easy to administer and effective instrument to screen for early cognitive impairment in community-based settings.

Primacy and recency effects in verbal memory are differentially associated with post-mortem frontal cortex p-tau 217 and 202 levels in a mixed sample of community-dwelling older adults

INTRODUCTION

Serial position effects in verbal memory are associated with in vivo fluid biomarkers and neuropathological outcomes in Alzheimer's disease (AD). To extend the biomarker literature, associations between serial position scores and postmortem levels of brain phosphorylated tau (p-tau) were examined, in the context of Braak stage of neurofibrillary tangle progression.

METHOD

Participants were 1091 community-dwelling adults (Mage = 80.2, 68.9% female) from the Rush University Religious Orders Study and Memory and Aging Project who were non-demented at enrollment and followed for a mean of 9.2 years until death. The CERAD Word List Memory test administered at baseline and within 1 year of death was used to calculate serial position (primacy, recency) and total recall scores. Proteomic analyses quantified p-tau 217 and 202 from dorsolateral prefrontal cortex samples. Linear regressions assessed associations between cognitive scores and p-tau with Braak stage as a moderator.

RESULTS

Cognitive status proximal to death indicated 34.7% were unimpaired, 26.2% met criteria for MCI, and 39.0% for dementia. Better baseline primacy recall, but not recency recall, was associated with lower p-tau 217 levels across Braak stages. Delayed recall showed a similar pattern as primacy. There was no main effect of immediate recall, but an interaction with Braak stages indicated a negative association with p-tau 217 level only in Braak V-VI. Within 1 year of death, there were no main effects for cognitive scores; however, recency, immediate and delayed recall scores interacted with Braak stage showing better recall was associated with lower p-tau 217 only in Braak V-VI. No associations were observed with p-tau 202.

CONCLUSIONS

Primacy recall measured in non-demented adults may be sensitive to emergent tau phosphorylation that occurs in the earliest stages of AD. Serial position scores may complement the routinely used delayed recall score and p-tau biomarkers to detect preclinical AD.

The relationship between learning slopes and Alzheimer's Disease biomarkers in cognitively unimpaired participants with and without subjective memory concerns

OBJECTIVE

Learning slopes represent serial acquisition of information during list-learning tasks. Although several calculations for learning slopes exist, the Learning Ratio (LR) has recently demonstrated the highest sensitivity toward changes in cognition and Alzheimer's disease (AD) biomarkers. However, investigation of learning slopes in cognitively unimpaired individuals with subjective memory concerns (SMC) has been limited. The current study examines the association of learning slopes to SMC, and the role of SMC in the relationship between learning slopes and AD biomarkers in cognitively unimpaired individuals.

METHOD

Data from 950 cognitively unimpaired participants from the Alzheimer's Disease Neuroimaging Initiative (aged 55 to 89) were used to calculate learning slope metrics. Learning slopes among those with and without SMC were compared with demographic correction, and the relationships of learning slopes with AD biomarkers of bilateral hippocampal volume and β-amyloid pathology were determined.

RESULTS

Learning slopes were consistently predictive of hippocampal atrophy and β-amyloid deposition. Results were heightened for LR relative to the other learning slopes. Additionally, interaction analyses revealed different associations between learning slopes and hippocampal volume as a function of SMC status.

CONCLUSIONS

Learning slopes appear to be sensitive to SMC and AD biomarkers, with SMC status influencing the relationship in cognitively unimpaired participants. These findings advance our knowledge of SMC, and suggest that LR - in particular - can be an important tool for the detection of AD pathology in both SMC and in AD clinical trials.

Sensitivity of memory subtests and learning slopes from the ADAS-Cog to distinguish along the continuum of the NIA-AA Research Framework for Alzheimer's Disease

Despite extensive use of the Alzheimer's Disease (AD) Assessment Scale - Cognitive Subscale (ADAS-Cog) in AD research, exploration of memory subtests or process scores from the measure has been limited. The current study sought to establish validity for the ADAS-Cog Word Recall Immediate and Delayed Memory subtests and learning slope scores by showing that they are sensitive to AD biomarker status. Word Recall subtest and learning slope scores were calculated for 441 participants from the Alzheimer's Disease Neuroimaging Initiative (aged 55 to 90). All participants were categorized using the NIA-AA Research Framework - based on PET-imaging of β-amyloid (A) and tau (T) deposition - as Normal AD Biomarkers (A-T-), Alzheimer's Pathologic Change (A + T-), or Alzheimer's disease (A + T+). Memory subtest and learning slope performances were compared between biomarker status groups, and with regard to how well they discriminated samples with (A + T+) and without (A-T-) biomarkers. Lower Word Recall memory subtest scores - and scores for a particular learning slope calculation, the Learning Ratio - were observed for the AD (A + T+) group than the other biomarker groups. Memory subtest and Learning Ratio scores further displayed fair to good receiver operator characteristics when differentiating those with and without AD biomarkers. When comparing across learning slopes, the Learning Ratio metric consistently outperformed others. ADAS-Cog memory subtests and the Learning Ratio score are sensitive to AD biomarker status along the continuum of the NIA-AA Research Framework, and the results offer criterion validity for use of these subtests and process scores as unique markers of memory capacity.

Cross-sectional associations of CSF tau levels with Rey's AVLT: A recency ratio study

OBJECTIVE

The preeminent in vivo cerebrospinal fluid (CSF) biomarkers of Alzheimer's disease (AD) are amyloid β 1-42 (Aβ42), phosphorylated Tau (p-tau), and total Tau (t-tau). The goal of this study was to examine how well traditional (total and delayed recall) and process-based (recency ratio [Rr]) measures derived from Rey's Auditory Verbal Learning test (AVLT) were associated with these biomarkers.

METHOD

Data from 235 participants (Mage = 65.5, SD = 6.9), who ranged from cognitively unimpaired to mild cognitive impairment, and for whom CSF values were available, were extracted from the Wisconsin Registry for Alzheimer's Prevention. Bayesian regression analyses were carried out using CSF scores as outcomes, AVLT scores as predictors, and controlling for demographic data and diagnosis.

RESULTS

We found moderate evidence that Rr was associated with both CSF p-tau (Bayesian factor [BFM] = 5.55) and t-tau (BFM = 7.28), above and beyond the control variables, while it did not correlate with CSF Aβ42 levels. In contrast, total and delayed recall scores were not linked with any of the AD biomarkers, in separate analyses. When comparing all memory predictors in a single regression, Rr remained the strongest predictor of CSF t-tau levels (BFM = 3.57).

CONCLUSIONS

Our findings suggest that Rr may be a better cognitive measure than commonly used AVLT scores to assess CSF levels of p-tau and t-tau in nondemented individuals. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Attenuation of amyloid-β-induced mitochondrial dysfunction by active components of anthocyanins in HT22 neuronal cells

Alzheimer's disease (AD) is a common form of neurodegenerative disease in the elderly. Amyloid-β (Aβ)-associated neurotoxicity is an important component of the neurodegenerative change in AD. Recent studies have revealed a beneficial effect of anthocyanins in improving learning and memory in AD animal models. Using cultured HT22 mouse hippocampal neuronal cells as an in vitro model, we examined in this study the protective effect of ten pure components of anthocyanins against Aβ ₄₂-induced cytotoxicity and also investigated the mechanism of their protective effects. We found that treatment of HT22 cells with the pure components of anthocyanins dose-dependently rescued Aβ ₄₂-induced cytotoxicity, with slightly different potencies. Using petunidin as a representative compound, we found that it enhanced mitochondrial homeostasis and function in Aβ ₄₂-treated HT22 cells. Mechanistically, petunidin facilitated β-catenin nuclear translocation and enhanced the interaction between β-catenin and TCF7, which subsequently upregulated mitochondrial homeostasis-related protein Mfn2, thereby promoting restoration of mitochondrial homeostasis and function in Aβ ₄₂-treated HT22 cells. Together, these results reveal that the pure components of anthocyanins have a strong protective effect in HT22 cells against Aβ ₄₂-induced cytotoxicity by ameliorating mitochondrial homeostasis and function in a β-catenin/TCF-dependent manner.

Longitudinal change in serial position scores in older adults with entorhinal and hippocampal neuropathologies

OBJECTIVE

Serial position scores on verbal memory tests are sensitive to early Alzheimer's disease (AD)-related neuropathological changes that occur in the entorhinal cortex and hippocampus. The current study examines longitudinal change in serial position scores as markers of subtle cognitive decline in older adults who may be in preclinical or at-risk states for AD.

METHODS

This study uses longitudinal data from the Religious Orders Study and the Rush Memory and Aging Project. Participants (n = 141) were included if they did not have dementia at enrollment, completed follow-up assessments, and died and were classified as Braak stage I or II. Memory tests were used to calculate serial position (primacy, recency), total recall, and episodic memory composite scores. A neuropathological evaluation quantified AD, vascular, and Lewy body pathologies. Mixed effects models were used to examine change in memory scores. Neuropathologies and covariates (age, sex, education, APOE e4) were examined as moderators.

RESULTS

Primacy scores declined (β = -.032, p < .001), whereas recency scores increased (β = .021, p = .012). No change was observed in standard memory measures. Greater neurofibrillary tangle density and atherosclerosis explained 10.4% of the variance in primacy decline. Neuropathologies were not associated with recency change.

CONCLUSIONS

In older adults with hippocampal neuropathologies, primacy score decline may be a sensitive marker of early AD-related changes. Tangle density and atherosclerosis had additive effects on decline. Recency improvement may reflect a compensatory mechanism. Monitoring for changes in serial position scores may be a useful in vivo method of tracking incipient AD.

Misinterpreting cognitive change over multiple timepoints: When practice effects meet age-related decline

OBJECTIVE

Practice effects (PE) on cognitive testing have been shown to delay detection of impairment and impede our ability to assess change. When decline over time is expected, as with older adults or progressive diseases, failure to adequately address PEs may lead to inaccurate conclusions because PEs artificially boost scores while pathology- or age-related decline reduces scores. Unlike most methods, a participant-replacement approach can separate pathology- or age-related decline from PEs; however, this approach has only been used across two timepoints. More than two timepoints make it possible to determine if PEs level out after the first follow-up, but it is analytically challenging because individuals may not be assessed at every timepoint.

METHOD

We examined 1,190 older adults who were cognitively unimpaired (n = 809) or had mild cognitive impairment (MCI; n = 381). Participants completed six neuropsychological measures at three timepoints (baseline, 12-month, 24-month). We implemented a participant-replacement method using generalized estimating equations in comparisons of matched returnees and replacements to calculate PEs.

RESULTS

Without accounting for PEs, cognitive function appeared to improve or stay the same. However, with the participant-replacement method, we observed significant PEs within both groups at all timepoints. PEs did not uniformly decrease across time; some-specifically on episodic memory measures-continued to increase beyond the first follow-up.

CONCLUSION

A replacement method of PE adjustment revealed significant PEs across two follow-ups. As expected in these older adults, accounting for PEs revealed cognitive decline. This, in turn, means earlier detection of cognitive deficits, including progression to MCI, and more accurate characterization of longitudinal change. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Correlation between ankle-brachial index and subtle cognitive decline

BACKGROUND

Subtle cognitive decline (SCD) is considered the early stage of Alzheimer's disease (AD) and is of great clinical significance for the prevention and treatment of AD. The ankle-brachial index (ABI) has been reported to be associated with cognitive impairment; however, there are few studies on the relationship between ABI and SCD.

METHODS

From August 2019 to April 2021, subjects were recruited to participate in a cognitive function test at the Shanghai Sixth People's Hospital. Based on the test results, 217 patients with SCD were selected as the experimental group and 259 patients with normal cognitive function were selected as the control group. The data of the two groups were compared, and the correlation between the ABI and cognitive decline was analyzed.

RESULTS

There were significant differences in age, sex, smoking status, hypertension, diabetes, triglycerides, serum creatinine, and ABI (p < .05)between the two groups. Logistic regression analysis showed that age, hypertension, diabetes, and ABI influenced cognitive decline(p < .05). After correcting for other factors, ABI was independently related to cognitive decline. Pearson's correlation analysis showed that a low ABI (<0.9) had a significant effect on memory and visual space of the cognitive domain (p < . 05).

CONCLUSIONS

ABI is significantly associated with SCD and may be a critical tool to predict early cognitive decline.

Advances and applications of fluids biomarkers in diagnosis and therapeutic targets of Alzheimer's disease

AIMS

Alzheimer's disease (AD) is a neurodegenerative disease with challenging early diagnosis and effective treatments due to its complex pathogenesis. AD patients are often diagnosed after the appearance of the typical symptoms, thereby delaying the best opportunity for effective measures. Biomarkers could be the key to resolving the challenge. This review aims to provide an overview of application and potential value of AD biomarkers in fluids, including cerebrospinal fluid, blood, and saliva, in diagnosis and treatment.

METHODS

A comprehensive search of the relevant literature was conducted to summarize potential biomarkers for AD in fluids. The paper further explored the biomarkers' utility in disease diagnosis and drug target development.

RESULTS

Research on biomarkers mainly focused on amyloid-β (Aβ) plaques, Tau protein abnormal phosphorylation, axon damage, synaptic dysfunction, inflammation, and related hypotheses associated with AD mechanisms. Aβ₄₂ , total Tau (t-Tau), and phosphorylated Tau (p-Tau), have been endorsed for their diagnostic and predictive capability. However, other biomarkers remain controversial. Drugs targeting Aβ have shown some efficacy and those that target BACE1 and Tau are still undergoing development.

CONCLUSION

Fluid biomarkers hold considerable potential in the diagnosis and drug development of AD. However, improvements in sensitivity and specificity, and approaches for managing sample impurities, need to be addressed for better diagnosis.

Brain Functional Alterations and Association with Cognition in People with Preclinical Subjective Cognitive Decline and Objective Subtle Cognitive Difficulties

Subjective cognitive decline (SCD) and objective subtle cognitive difficulties (Obj-SCD) are considered the initial stages of aberrant cognition prior to mild cognitive impairment (MCI) due to Alzheimer's disease (AD). We aimed to determine the difference of brain function of SCD and Obj-SCD, furthermore, to figure out which one could be the marker of early AD. One hundred and eighty-five participants were enrolled in this study to determine the amyloid pathology and glucose metabolism changes in SCD and Obj-SCD. The association of amyloid deposition and glucose metabolism with cognitive domains were also investigated. Obj-SCD displayed significantly increased amyloid deposition in frontal and temporal lobes compared to SCD and normal cognitive control (NCC). No difference of amyloid deposition between SCD and NCC, and no difference of glucose metabolism among the three groups were observed. Amyloid deposition was associated with function of memory, language and executive domains, and glucose metabolism was only associated with executive function in Obj-SCD. Amyloid deposition was only associated with executive function in SCD. Obj-SCD could be the early stage of AD, which displayed significant increased amyloid deposition, and the increased amyloid deposition was associated with cognitive function in different domains.

Circulatory proteins relate cardiovascular disease to cognitive performance: A mendelian randomisation study

Background and objectives: Mechanistic research suggests synergistic effects of cardiovascular disease (CVD) and dementia pathologies on cognitive decline. Interventions targeting proteins relevant to shared mechanisms underlying CVD and dementia could also be used for the prevention of cognitive impairment. Methods: We applied Mendelian randomisation (MR) and colocalization analysis to investigate the causal relationships of 90 CVD-related proteins measured by the Olink CVD I panel with cognitive traits. Genetic instruments for circulatory protein concentrations were obtained using a meta-analysis of genome-wide association studies (GWAS) from the SCALLOP consortium (N = 17,747) based on three sets of criteria: 1) protein quantitative trait loci (pQTL); 2) cis-pQTL (pQTL within ±500 kb from the coding gene); and 3) brain-specific cis-expression QTL (cis-eQTL) which accounts for coding gene expression based on GTEx8. Genetic associations of cognitive performance were obtained from GWAS for either: 1) general cognitive function constructed using Principal Component Analysis (N = 300,486); or, 2) g Factor constructed using genomic structural equation modelling (N = 11,263-331,679). Findings for candidate causal proteins were replicated using a separate protein GWAS in Icelanders (N = 35,559). Results: A higher concentration of genetically predicted circulatory myeloperoxidase (MPO) was nominally associated with better cognitive performance (p < 0.05) using different selection criteria for genetic instruments. Particularly, brain-specific cis-eQTL predicted MPO, which accounts for protein-coding gene expression in brain tissues, was associated with general cognitive function (βWald = 0.22, PWald = 2.4 × 10-4). The posterior probability for colocalization (PP.H4) of MPO pQTL with the g Factor was 0.577. Findings for MPO were replicated using the Icelandic GWAS. Although we did not find evidence for colocalization, we found that higher genetically predicted concentrations of cathepsin D and CD40 were associated with better cognitive performance and a higher genetically predicted concentration of CSF-1 was associated with poorer cognitive performance. Conclusion: We conclude that these proteins are involved in shared pathways between CVD and those for cognitive reserve or affecting cognitive decline, suggesting therapeutic targets able to reduce genetic risks conferred by cardiovascular disease.

Insight into the role of adult hippocampal neurogenesis in aging and Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia and seriously affects the quality of life of the elderly. Neurodegeneration is closely related to hippocampal dysfunction in AD patients. The hippocampus is key to creating new memories and is also one of the first areas of the brain to deteriorate with age. Mammalian neurogenesis occurs mainly in the hippocampus. Recent studies have confirmed that neurogenesis in the hippocampus is sustainable but decreases with age, which seriously affects the learning and memory function of AD patients. At present, our understanding of neurogenesis is still relatively shallow, especially pertaining to the influence and role of neurogenesis during aging and cognitive deficits in AD patients. Interestingly, many recent studies have described the characteristics of neurogenesis in animal models. This article reviews the progress of neurogenesis research in the context of aging and AD to provide new insights into neurogenesis.

Medial temporal lobe structure, mnemonic and perceptual discrimination in healthy older adults and those at risk for mild cognitive impairment

Cognitive tests sensitive to the integrity of the medial temporal lobe (MTL), such as mnemonic discrimination of perceptually similar stimuli, may be useful early markers of risk for cognitive decline in older populations. Perceptual discrimination of stimuli with overlapping features also relies on MTL but remains relatively unexplored in this context. We assessed mnemonic discrimination in two test formats (Forced Choice, Yes/No) and perceptual discrimination of objects and scenes in 111 community-dwelling older adults at different risk status for cognitive impairment based on neuropsychological screening. We also investigated associations between performance and MTL sub-region volume and thickness. The at-risk group exhibited reduced entorhinal thickness and impaired perceptual and mnemonic discrimination. Perceptual discrimination impairment partially explained group differences in mnemonic discrimination and correlated with entorhinal thickness. Executive dysfunction accounted for Yes/No deficits in at-risk adults, demonstrating the importance of test format for the interpretation of memory decline. These results suggest that perceptual discrimination tasks may be useful tools for detecting incipient cognitive impairment related to reduced MTL integrity in nonclinical populations.

Oxidative Stress and Natural Antioxidants: Back and Forth in the Neurological Mechanisms of Alzheimer's Disease

Alzheimer's disease (AD) is characterized by the progressive degeneration of neuronal cells. With the increase in aged population, there is a prevalence of irreversible neurodegenerative changes, causing a significant mental, social, and economic burden globally. The factors contributing to AD are multidimensional, highly complex, and not completely understood. However, it is widely known that aging, neuroinflammation, and excessive production of reactive oxygen species (ROS), along with other free radicals, substantially contribute to oxidative stress and cell death, which are inextricably linked. While oxidative stress is undeniably important in AD, limiting free radicals and ROS levels is an intriguing and potential strategy for deferring the process of neurodegeneration and alleviating associated symptoms. Therapeutic compounds from natural sources have recently become increasingly accepted and have been effectively studied for AD treatment. These phytocompounds are widely available and a multitude of holistic therapeutic efficiencies for treating AD owing to their antioxidant, anti-inflammatory, and biological activities. Some of these compounds also function by stimulating cholinergic neurotransmission, facilitating the suppression of beta-site amyloid precursor protein-cleaving enzyme 1, α-synuclein, and monoamine oxidase proteins, and deterring the occurrence of AD. Additionally, various phenolic, flavonoid, and terpenoid phytocompounds have been extensively described as potential palliative agents for AD progression. Preclinical studies have shown their involvement in modulating the cellular redox balance and minimizing ROS formation, displaying them as antioxidant agents with neuroprotective abilities. This review emphasizes the mechanistic role of natural products in the treatment of AD and discusses the various pathological hypotheses proposed for AD.

Impact of the Cannabinoid System in Alzheimer's Disease

Cannabinoids are compounds isolated from cannabis and are also widely present in both nervous and immune systems of animals. In recent years, with in-depth research on cannabinoids, their clinical medicinal value has been evaluated, and many exciting achievements have been continuously accumulating, especially in the field of neurodegenerative disease. Alzheimer's disease is the most common type of neurodegenerative disease that causes dementia and has become a global health problem that seriously impacts human health today. In this review, we discuss the therapeutic potential of cannabinoids for the treatment of Alzheimer's disease. How cannabinoids act on different endocannabinoid receptor subtypes to regulate Alzheimer's disease and the roles of the endocannabinoid system in Alzheimer's disease are outlined, and the underlying mechanisms are discussed. Finally, we summarize the most relevant opportunities of cannabinoid pharmacology related to Alzheimer's disease and discuss the potential usefulness of cannabinoids in the clinical treatment of Alzheimer's disease.

Altered functional connectivity pattern of hippocampal subfields in individuals with objectively-defined subtle cognitive decline and its association with cognition and cerebrospinal fluid biomarkers

Recent studies have shown that in the preclinical phase of Alzheimer's disease (AD), subtle cognitive changes can be detected using sensitive neuropsychological measures, and have proposed the concept of objectively-defined subtle cognitive decline (Obj-SCD). We aimed to assess the functional alteration of hippocampal subfields in individuals with Obj-SCD and its association with cognition and pathological biomarkers. Forty-two participants with cognitively normal (CN), 29 with Obj-SCD, and 55 with mild cognitive impairment (MCI) were retrospectively collected from the ADNI database. Neuropsychological performance, functional MRI, and cerebrospinal fluid (CSF) data were obtained. We calculated the seed-based functional connectivity (FC) of hippocampal subfields (cornu ammonis1 [CA1], CA2/3/dentate gyrus [DG], and subiculum) with whole-brain voxels. Additionally, we analyzed the correlation between FC values of significantly altered regions and neuropsychological performance and CSF biomarkers. The Obj-SCD group showed lower FC between left CA1-CA2/3/DG and right thalamus and higher FC between right subiculum and right superior parietal gyrus (SPG) compared with the CN and MCI groups. In the Obj-SCD group, FC values between left CA2/3/DG and right thalamus were positively associated with Auditory Verbal Learning Test (AVLT) recognition (r = 0.395, p = 0.046) and CSF Aβ1-42 levels (r = 0.466, p = 0.019), and FC values between left CA1 and right thalamus were positively correlated with CSF Aβ1-42 levels (r = 0.530, p = 0.006). Taken together, dysfunction in CA1-CA2/3/DG subregions suggests subtle cognitive impairment and AD-specific pathological changes in individuals with Obj-SCD. Additionally, increased subiculum connectivity may indicate early functional compensation for subtle cognitive changes.

Engineered Extracellular Vesicles with SHP2 High Expression Promote Mitophagy for Alzheimer's Disease Treatment

Mitochondrial dysfunction is a fundamental pathological feature of Alzheimer's disease (AD). However, toxicity and poor brain enrichment of existing mitophagy inducers limit their further applications. In this study, a platform for AD therapy is developed using nanosized mesenchymal-stem-cells-derived extracellular vesicles with tyrosine phosphatase-2 (SHP2) high-expression (MSC-EVs-SHP2). The high blood-brain barrier penetration ability of MSC-EVs-SHP2 is demonstrated in AD-mice, facilitating SHP2 delivery to the brain. In addition, MSC-EVs-SHP2 significantly induces mitophagy of neuronal cells, which alleviates mitochondrial damage-mediated apoptosis and NLRP3 inflammasome activation. Mitophagy further diminishes neuronal cells apoptosis and neuroinflammation, culminating with rescued synaptic loss and cognitive decline in an AD mouse model. The EV-engineering technology provides a potential platform for effective AD therapy by inducing mitophagy.

Recent Progress in Research on Mechanisms of Action of Natural Products against Alzheimer's Disease: Dietary Plant Polyphenols

Alzheimer's disease (AD) is an incurable degenerative disease of the central nervous system and the most common type of dementia in the elderly. Despite years of extensive research efforts, our understanding of the etiology and pathogenesis of AD is still highly limited. Nevertheless, several hypotheses related to risk factors for AD have been proposed. Moreover, plant-derived dietary polyphenols were also shown to exert protective effects against neurodegenerative diseases such as AD. In this review, we summarize the regulatory effects of the most well-known plant-derived dietary polyphenols on several AD-related molecular mechanisms, such as amelioration of oxidative stress injury, inhibition of aberrant glial cell activation to alleviate neuroinflammation, inhibition of the generation and promotion of the clearance of toxic amyloid-β (Aβ) plaques, inhibition of cholinesterase enzyme activity, and increase in acetylcholine levels in the brain. We also discuss the issue of bioavailability and the potential for improvement in this regard. This review is expected to encourage further research on the role of natural dietary plant polyphenols in the treatment of AD.

Association between age-related hearing loss with tinnitus and cognitive performance in older community-dwelling Chinese adults

AIM

To examine how the severity of age-related hearing loss (ARHL) and tinnitus or the presentation of ARHL with tinnitus is associated with overall cognition, in terms of specific cognitive domains in older community-dwelling Chinese adults.

METHODS

The study recruited 429 participants aged ≥58 years (mean age, 72.91 ± 7.014 years; female proportion, 57.30%), excluding those with dementia, disability, and severe mental illness. Patients were classified into normal cognition, pre-mild cognitive impairment (pre-MCI), and MCI according to the normative z-scores of neuropsychological test battery. The severity of ARHL and tinnitus was measured by pure-tone audiometry and the Tinnitus Handicap Inventory. Cognitive impairment and low functions in specific cognitive domains were used as dependent variables in multiple regression analyses adjusted for covariates.

RESULTS

ARHL severity was positively associated with MCI and low executive function, delayed memory, and language function. Only individuals with mild (odds ratio (OR) 1.791; CI, 0.952-3.373; P = 0.071), and moderate and the disaster tinnitus (OR, 2.493; CI, 0.982-6.328; P = 0.055) were marginally associated with increased odds of MCI in model 1. Individuals with ARHL and tinnitus (OR, 3.888, CI = 1.481-10.205; OR, 4.471, CI = 1.636-12.219) were independently associated with high risk for MCI in models 1 and 2.

CONCLUSIONS

ARHL severity and the presentation of ARHL or ARHL with tinnitus were associated with overall cognition. ARHL severity was independently associated with executive function, delayed memory, and language function. The association between tinnitus severity and cognition is not clear. But the group with ARHL and tinnitus is a high-risk group with cognitive impairment.

CLINICALTRIALS

gov identifier: NCT2017K020.

Associating persistent self-reported cognitive decline with neurocognitive decline in older breast cancer survivors using machine learning: The Thinking and Living with Cancer study

INTRODUCTION

Many cancer survivors report cognitive problems following diagnosis and treatment. However, the clinical significance of patient-reported cognitive symptoms early in survivorship can be unclear. We used a machine learning approach to determine the association of persistent self-reported cognitive symptoms two years after diagnosis and neurocognitive test performance in a prospective cohort of older breast cancer survivors.

MATERIALS AND METHODS

We enrolled breast cancer survivors with non-metastatic disease (n = 435) and age- and education-matched non-cancer controls (n = 441) between August 2010 and December 2017 and followed until January 2020; we excluded women with neurological disease and all women passed a cognitive screen at enrollment. Women completed the FACT-Cog Perceived Cognitive Impairment (PCI) scale and neurocognitive tests of attention, processing speed, executive function, learning, memory and visuospatial ability, and timed activities of daily living assessments at enrollment (pre-systemic treatment) and annually to 24 months, for a total of 59 individual neurocognitive measures. We defined persistent self-reported cognitive decline as clinically meaningful decline (3.7+ points) on the PCI scale from enrollment to twelve months with persistence to 24 months. Analysis used four machine learning models based on data for change scores (baseline to twelve months) on the 59 neurocognitive measures and measures of depression, anxiety, and fatigue to determine a set of variables that distinguished the 24-month persistent cognitive decline group from non-cancer controls or from survivors without decline.

RESULTS

The sample of survivors and controls ranged in age from were ages 60-89. Thirty-three percent of survivors had self-reported cognitive decline at twelve months and two-thirds continued to have persistent decline to 24 months (n = 60). Least Absolute Shrinkage and Selection Operator (LASSO) models distinguished survivors with persistent self-reported declines from controls (AUC = 0.736) and survivors without decline (n = 147; AUC = 0.744). The variables that separated groups were predominantly neurocognitive test performance change scores, including declines in list learning, verbal fluency, and attention measures.

DISCUSSION

Machine learning may be useful to further our understanding of cancer-related cognitive decline. Our results suggest that persistent self-reported cognitive problems among older women with breast cancer are associated with a constellation of mild neurocognitive changes warranting clinical attention.

Increased regional white matter hyperintensity volume in objectively-defined subtle cognitive decline and mild cognitive impairment

White matter hyperintensities (WMH), a marker of small vessel cerebrovascular disease, increase risk of developing mild cognitive impairment (MCI) and Alzheimer's disease (AD). Less is known about the extent and pattern of WMH in pre-MCI stages, such as among those with objectively-defined subtle cognitive decline (Obj-SCD). Five hundred and fifty-nine Alzheimer's Disease Neuroimaging Initiative participants (170 cognitively unimpaired [CU]; 83 Obj-SCD; 306 MCI) free of clinical dementia or stroke completed neuropsychological testing and MRI exams. ANCOVA models compared cognitive groups on regional WMH adjusting for age, sex, and apolipoprotein E (APOE) ɛ4 frequency. Compared with the CU group, those with Obj-SCD had greater temporal, occipital, and frontal WMH whereas those with MCI had higher WMH volume across all regions (p's < 0.01). No differences in WMH volume were observed between the Obj-SCD and MCI groups (p's > 0.05). Findings add to growing evidence of associations between Obj-SCD and imaging biomarkers, providing support for utility of these criteria to capture subtle cognitive changes that are biologically based.

Associations of plasma phosphorylated tau181 and neurofilament light chain with brain amyloid burden and cognition in objectively defined subtle cognitive decline patients

AIMS

There is increasing evidence that plasma biomarkers are specific biomarkers for Alzheimer's disease (AD) pathology, but their potential utility in Obj-SCD (objectively defined subtle cognitive decline) remains unclear.

METHODS

A total of 234 subjects, including 65 with brain amyloid beta (Aβ) negative normal cognition (Aβ- NC), 58 with Aβ-positive NC (Aβ+ NC), 63 with Aβ- Obj-SCD, and 48 with Aβ+ Obj-SCD were enrolled. Plasma Aβ42, Aβ40, Aβ42/Aβ40 ratio, phosphorylated tau181 (p-tau181), neurofilament light chain (NfL), and total tau (T-tau) were measured using Simoa assays. Logistic and linear regression analyses were used to examine the relationship between plasma biomarkers and brain amyloid, cognition, and imaging measures adjusting for age, sex, education, APOE ε4 status, and vascular risk scores. Receiver operating characteristics were used to evaluate the discriminative validity of biomarkers.

RESULTS

After adjustment, only plasma p-tau181 and NfL were significantly elevated in Aβ+ Obj-SCD participants compared to Aβ- NC group. Elevated p-tau181 was associated with brain amyloid accumulation, worse cognitive performance (visual episodic memory, executive function, and visuospatial function), and hippocampal atrophy. These associations mainly occurred in Aβ+ individuals. In contrast, higher NfL was correlated with brain amyloid burden and verbal memory decline. These associations predominantly occurred in Aβ- individuals. The adjusted diagnostic model combining p-tau181 and NfL levels showed the best performance in identifying Aβ+ Obj-SCD from Aβ- NC [area under the curve (AUC) = 0.814], which did not differ from the adjusted p-tau181 model (AUC = 0.763).

CONCLUSIONS

Our findings highlight that plasma p-tau181, alone or combined with NfL, contributes to identifying high-risk AD populations.

Application and prospect for generative adversarial networks in cross-modality reconstruction of medical images

Cross-modality reconstruction of medical images refers to predicting the image from one modality to another so as to achieve more accurate personalized medicine. Generative adversarial networks is the most commonly used deep learning technique in cross-modality reconstruction. It can generate realistic images by learning features from implicit distributions that follow the distributions of real data and then reconstruct the image of another modality rapidly. With the sharp increase in clinical demand for multi-modality medical image, this technology has been widely used in the task of cross modal reconstruction between different medical image modalities, such as magnetic resonance imaging, computed tomography and positron emission computed tomography. It can achieve accurate and efficient cross-modality image reconstruction in different parts of the body, such as the brain, heart, etc. In addition, although GAN has achieved some success in cross-modality reconstruction, its stability, generalization ability, and accuracy still need further research and improvement.

Tau levels are higher in objective subtle cognitive decline but not subjective memory complaint

BACKGROUND

The 2018 NIA-AA Alzheimer's Disease (AD) Research Framework states that subtle cognitive decline in cognitively unimpaired individuals can be measured by subjective reports or evidence of objective decline on neuropsychological measures. Both subjective memory complaint (SMC) and objective subtle cognitive decline (Obj-SCD) have been shown to be associated with future cognitive decline and AD biomarkers. We examined whether there are differences in tau PET levels between (a) SMC- vs. SMC+ participants, (b) Obj-SCD- vs. Obj-SCD+ participants, and (c) participants with overlapping vs. discrepant SMC and Obj-SCD classifications.

METHODS

Cognitively unimpaired participants from the Alzheimer's Disease Neuroimaging Initiative (ADNI; n = 236) were classified at baseline as positive or negative for SMC (SMC- n = 77; SMC+ n = 159) based on the first 12 items of the Cognitive Change Index and/or classified as positive or negative for Obj-SCD (Obj-SCD- n = 173; Obj-SCD+ n = 63) based on previously defined neuropsychological criteria. Analyses of covariance, adjusting for age, sex, APOE ε4 carrier status, and pulse pressure, examined the group differences in tau PET (AV-1451) using a composite standardized uptake variable ratio (SUVR) for regions consistent with Braak stage III/IV. The chi-squared tests examined the tau positivity rates across the groups.

RESULTS

Obj-SCD+ participants had higher tau continuous SUVR levels (p = .035, ηp2 = .019) and higher rates of tau positivity (15.8% Obj-SCD- vs. 30.2% Obj-SCD+) than Obj-SCD- participants. Neither tau levels (p = .381, ηp2 = .003) nor rates of tau positivity (18.2% SMC- and 20.1% SMC+) differed between the SMC groups. There was very little agreement between SMC and Obj-SCD classifications (42%; κ = 0.008, p = .862). Participants who were Obj-SCD+ without SMC had the highest tau PET levels and differed from participants who were SMC+ without Obj-SCD (p = .022). Tau levels in participants with both SMC and Obj-SCD did not differ from those with only Obj-SCD (p = .216). Tau positivity rates across the SMC-/Obj-SCD-, SMC+/Obj-SCD-, SMC-/Obj-SCD+, and SMC+/Obj-SCD+ groups were 10.5%, 18.1%, 40.0%, and 25.6%, respectively.

CONCLUSION

Participants with Obj-SCD had a greater tau PET burden than those without Obj-SCD, but SMC was not associated with higher tau levels. The combination of SMC and Obj-SCD did not have higher tau levels than Obj-SCD alone. Findings add to the evidence that the Obj-SCD classification is associated with AD biomarkers and faster cognitive decline in ADNI participants, but further work is needed to validate this approach in more representative/diverse cohorts.

Impaired type I interferon signaling activity implicated in the peripheral blood transcriptome of preclinical Alzheimer's disease

Background

Subjective or objective subtle cognitive decline (SCD) is considered the preclinical manifestation of Alzheimer's disease (AD), which is a potentially crucial window for preventing or delaying the progression of the disease.

Methods

To explore the potential mechanism of disease progression and identify relevant biomarkers, we comprehensively assessed the peripheral blood transcriptomic alterations in SCD, covering lncRNA, mRNA, and miRNA.

Findings

Dysregulated protein-coding mRNA at both gene and isoform levels implicated impairment in the type I interferon signaling pathway in SCD. Specifically, this pathway was regulated by the transcription factor STAT1 and ncRNAs NRIR and has-miR-146a-5p. The miRNA-mRNA-lncRNA co-expression network revealed hub genes for the interferon module. Individuals with lower interferon signaling activity and lower expression of a hub gene STAT1 exhibited a higher conversion rate to mild cognitive impairment (MCI).

Interpretation

Our findings illustrated the down-regulation of interferon signaling activity would potentially increase the risk of disease progression and thus serve as a pre-disease biomarker.

Funding

This work was partly supported by National Key R&D Program of China (2020YFA0712403), National Natural Science Foundation of China (61932008), Shanghai Municipal Science and Technology Major Project (2018SHZDZX01), the 111 Project (No. B18015) of China, Greater Bay Area Institute of Precision Medicine (Guangzhou) (Grand No. IPM21C008), Natural Science Foundation of Shanghai (21ZR1403200), and Shanghai Center for Brain Science and Brain-Inspired Technology.

Association Between Human Blood Metabolome and the Risk of Alzheimer's Disease

OBJECTIVE

Alzheimer's disease (AD) is the most common degenerative neurological disorder with limited therapeutic options. Therefore, it is particularly important to explore the potential biomarkers implicated in the occurrence and progression of AD prior to clinical testing.

METHODS

We selected 119 unique blood metabolites from 3 metabolome genome-wide association studies (GWASs) with 147,827 European participants. Summary data about AD were obtained from a GWAS meta-analysis with 63,926 European individuals from the International Genomics of Alzheimer's Project. MR analyses were performed to assess the associations of blood metabolites with AD, and a phenome-wide MR analysis was further applied to ascertain the potential on-target side effects of metabolite interventions.

RESULTS

Four metabolites were identified as causal mediators for AD, including epiandrosterone sulfate (odds ratio [OR] per SD increase: 0.60; 95% confidence interval [CI]: 0.51-0.71; P=6.14×10^-9 ), 5alpha-androstan-3beta-17beta-diol disulfate (OR per SD increase: 0.69; 95% CI: 0.57-0.84; P=1.98×10^-4 ), sphingomyelin (OR per SD increase: 2.53; 95% CI: 1.78-3.59; P=2.10×10^-7 ), and glutamine (OR per SD increase: 0.83; 95% CI: 0.77-0.89; P=2.09×10^-6 ). Phenome-wide MR analysis showed that epiandrosterone sulfate, 5alpha-androstan-3beta-17beta-diol disulfate and sphingomyelin mediated the risk of multiple diseases, and glutamine had beneficial effects on the risk of 4 diseases.

INTERPRETATION

Genetically predicted increased epiandrosterone sulfate, 5alpha-androstan-3beta-17beta-diol disulfate and glutamine might be associated with a decreased risk of AD, while sphingomyelin was associated with an increased risk. Side-effect profiles were characterized to help inform drug target prioritization, and glutamine might be a promising target for the prevention and treatment of AD with no predicted detrimental side effects. This article is protected by copyright. All rights reserved.

Validation of and Demographically Adjusted Normative Data for the Learning Ratio Derived from the RAVLT in Robustly Intact Older Adults

BACKGROUND

The learning ratio (LR) is a novel learning slope score that was developed to identify learning more accurately by considering the proportion of information learned after the first trial of a multi-trial learning task. Specifically, LR is the number of items learned after trial one divided by the number of items yet to be learned. Although research on LR has been promising, convergent validation, clinical characterization, and demographic norming of this LR metric are warranted to understand its clinical utility when derived from the Rey Auditory Verbal Learning Test (RAVLT).

METHOD

Data from 674 robustly cognitively intact older participants from the Alzheimer's Disease Neuroimaging Initiative (aged 54- 89) were used to calculate the LR metric. Comparison of LR's relationship with standard memory measures was undertaken relative to other traditional learning slope metrics. In addition, retest reliability at 6, 12, and 24 months was examined, and demographically adjusted normative comparisons were developed.

RESULTS

Lower LR scores were associated with poorer performances on memory measures, and LR scores outperformed traditional learning slope calculations across all analyses. Retest reliability exceeded acceptability thresholds across time, and demographically adjusted normative equations suggested better performance for cognitively intact participants than those with mild cognitive impairment.

CONCLUSIONS

These results suggest that this LR score possesses sound retest reliability and can better reflect learning capacity than traditional learning slope calculations. With the added development and validation of regression-based normative comparisons, these findings support the use of the RAVLT LR as a clinical tool to inform clinical decision-making and treatment.

Clinical Progression of Baseline Risk States for Mild Cognitive Impairment

BACKGROUND

This memory-clinic study joins efforts to study earliest clinical signs and symptoms of Alzheimer's disease and related dementias: subjective reports and objective neuropsychological test performance.

OBJECTIVE

The memory-clinic denoted two clinical "grey zones": 1) subjective cognitive decline (SCD; n = 107) with normal objective test scores, and 2) isolated low test scores (ILTS; n = 74) without subjective complaints to observe risk for future decline.

METHODS

Initial and annual follow-up clinical research evaluations and consensus diagnosis were used to evaluate baseline characteristics and clinical progression over 2.7 years, compared to normal controls (NC; n = 117).

RESULTS

The ILTS group was on average older than the NC and SCD groups. They had a higher proportion of people identifying as belonging to a minoritized racial group. The SCD group had significantly more years of education than the ILTS group. Both ILTS and SCD groups had increased risk of progression to mild cognitive impairment. Older age, minoritized racial identity, and baseline cognitive classification were risk factors for progression.

CONCLUSION

The two baseline risk groups look different from each other, especially with respect to demographic correlates, but both groups predict faster progression than controls, over and above demographic differences. Varied presentations of early risk are important to recognize and may advance cognitive health equity in aging.

Network alterations underlying anxiety symptoms in early multiple sclerosis

BACKGROUND

Anxiety, often seen as comorbidity in multiple sclerosis (MS), is a frequent neuropsychiatric symptom and essentially affects the overall disease burden. Here, we aimed to decipher anxiety-related networks functionally connected to atrophied areas in patients suffering from MS.

METHODS

Using 3-T MRI, anxiety-related atrophy maps were generated by correlating longitudinal cortical thinning with the severity of anxiety symptoms in MS patients. To determine brain regions functionally connected to these maps, we applied a technique termed "atrophy network mapping". Thereby, the anxiety-related atrophy maps were projected onto a large normative connectome (n = 1000) performing seed-based functional connectivity. Finally, an instructed threat paradigm was conducted with regard to neural excitability and effective connectivity, using transcranial magnetic stimulation combined with high-density electroencephalography.

RESULTS

Thinning of the left dorsal prefrontal cortex was the only region that was associated with higher anxiety levels. Atrophy network mapping identified functional involvement of bilateral prefrontal cortex as well as amygdala and hippocampus. Structural equation modeling confirmed that the volumes of these brain regions were significant determinants that influence anxiety symptoms in MS. We additionally identified reduced information flow between the prefrontal cortex and the amygdala at rest, and pathologically increased excitability in the prefrontal cortex in MS patients as compared to controls.

CONCLUSION

Anxiety-related prefrontal cortical atrophy in MS leads to a specific network alteration involving structures that resemble known neurobiological anxiety circuits. These findings elucidate the emergence of anxiety as part of the disease pathology and might ultimately enable targeted treatment approaches modulating brain networks in MS.

Cross-sectional associations of CSF tau levels with Rey's AVLT: A recency ratio study

OBJECTIVE

The preeminent in vivo cerebrospinal fluid (CSF) biomarkers of Alzheimer's disease (AD) are amyloid β 1-42 (Aβ42), phosphorylated Tau (p-tau), and total Tau (t-tau). The goal of this study was to examine how well traditional (total and delayed recall) and process-based (recency ratio [Rr]) measures derived from Rey's Auditory Verbal Learning test (AVLT) were associated with these biomarkers.

METHOD

Data from 235 participants (M_age = 65.5, SD = 6.9), who ranged from cognitively unimpaired to mild cognitive impairment, and for whom CSF values were available, were extracted from the Wisconsin Registry for Alzheimer's Prevention. Bayesian regression analyses were carried out using CSF scores as outcomes, AVLT scores as predictors, and controlling for demographic data and diagnosis.

RESULTS

We found moderate evidence that Rr was associated with both CSF p-tau (Bayesian factor [BF_M] = 5.55) and t-tau (BF_M = 7.28), above and beyond the control variables, while it did not correlate with CSF Aβ42 levels. In contrast, total and delayed recall scores were not linked with any of the AD biomarkers, in separate analyses. When comparing all memory predictors in a single regression, Rr remained the strongest predictor of CSF t-tau levels (BF_M = 3.57).

CONCLUSIONS

Our findings suggest that Rr may be a better cognitive measure than commonly used AVLT scores to assess CSF levels of p-tau and t-tau in nondemented individuals. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

β-Amyloid in blood neuronal-derived extracellular vesicles is elevated in cognitively normal adults at risk of Alzheimer's disease and predicts cerebral amyloidosis

Background

Blood biomarkers that can be used for preclinical Alzheimer’s disease (AD) diagnosis would enable trial enrollment at a time when the disease is potentially reversible. Here, we investigated plasma neuronal-derived extracellular vesicle (nEV) cargo in patients along the Alzheimer’s continuum, focusing on cognitively normal controls (NCs) with high brain β-amyloid (Aβ) loads (Aβ+).

Methods

The study was based on the Sino Longitudinal Study on Cognitive Decline project. We enrolled 246 participants, including 156 NCs, 45 amnestic mild cognitive impairment (aMCI) patients, and 45 AD dementia (ADD) patients. Brain Aβ loads were determined using positron emission tomography. NCs were classified into 84 Aβ− NCs and 72 Aβ+ NCs. Baseline plasma nEVs were isolated by immunoprecipitation with an anti-CD171 antibody. After verification, their cargos, including Aβ, tau phosphorylated at threonine 181, and neurofilament light, were quantified using a single-molecule array. Concentrations of these cargos were compared among the groups, and their receiver operating characteristic (ROC) curves were constructed. A subset of participants underwent follow-up cognitive assessment and magnetic resonance imaging. The relationships of nEV cargo levels with amyloid deposition, longitudinal changes in cognition, and brain regional volume were explored using correlation analysis. Additionally, 458 subjects in the project had previously undergone plasma Aβ quantification.

Results

Only nEV Aβ was included in the subsequent analysis. We focused on Aβ₄₂ in the current study. After normalization of nEVs, the levels of Aβ₄₂ were found to increase gradually across the cognitive continuum, with the lowest in the Aβ− NC group, an increase in the Aβ+ NC group, a further increase in the aMCI group, and the highest in the ADD group, contributing to their diagnoses (Aβ− NCs vs. Aβ+ NCs, area under the ROC curve values of 0.663; vs. aMCI, 0.857; vs. ADD, 0.957). Furthermore, nEV Aβ₄₂ was significantly correlated with amyloid deposition, as well as longitudinal changes in cognition and entorhinal volume. There were no differences in plasma Aβ levels among NCs, aMCI, and ADD individuals.

Conclusions

Our findings suggest the potential use of plasma nEV Aβ₄₂ levels in diagnosing AD-induced cognitive impairment and Aβ+ NCs. This biomarker reflects cortical amyloid deposition and predicts cognitive decline and entorhinal atrophy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13195-022-01010-x.

A Single Baseline Amyloid Positron Emission Tomography Could Be Sufficient for Predicting Alzheimer's Disease Conversion in Mild Cognitive Impairment

OBJECTIVE

Baseline amyloid burden in mild cognitive impairment (MCI) has been linked to conversion to Alzheimer's disease (AD), but the comparison of baseline and longitudinal changes in amyloid burden for predicting AD remains unresolved. The objectives of this study aimed to compare the prognostic ability of baseline and longitudinal changes in amyloid burden in MCI patients.

METHODS

Seventy-five individuals with MCI were recruited and examined annually by clinical interviews for a mean follow-up of 24 months (range, 11.6-42.0). [18F]Florbetaben positron emission tomography (PET) scans were performed. T1-weighted 3D volumes were acquired for co-registration, and to define regions of interest. We examined whether baseline and longitudinal amyloid burden changes can improve AD conversion by Cox proportional hazard model analysis and receiver operating characteristic (ROC) curve analysis.

RESULTS

Cox proportional hazards model analysis showed that baseline amyloid burden was significantly associated with increased risk of conversion to AD (hazard ratio [HR]=10.0; 95% confidence interval [CI], 1.15-85.39; p=0.04), but longitudinal amyloid burden changes was not (HR=0.2; 95% CI, 0.02-1.18; p=0.07). When predicting AD, longitudinal amyloid burden changes had better ROC accuracy of 65.2% (95% CI, 48.4-82.0) than baseline amyloid burden of 59.6% (95% CI, 40.3-79.0), without statistical significance in pairwise comparison.

CONCLUSION

A single baseline amyloid PET could be sufficient in the prediction of AD conversion in MCI.

Peripheral Pathways to Neurovascular Unit Dysfunction, Cognitive Impairment, and Alzheimer’s Disease

Alzheimer’s disease (AD) is the most common form of dementia. It was first described more than a century ago, and scientists are acquiring new data and learning novel information about the disease every day. Although there are nuances and details continuously being unraveled, many key players were identified in the early 1900’s by Dr. Oskar Fischer and Dr. Alois Alzheimer, including amyloid-beta (Aβ), tau, vascular abnormalities, gliosis, and a possible role of infections. More recently, there has been growing interest in and appreciation for neurovascular unit dysfunction that occurs early in mild cognitive impairment (MCI) before and independent of Aβ and tau brain accumulation. In the last decade, evidence that Aβ and tau oligomers are antimicrobial peptides generated in response to infection has expanded our knowledge and challenged preconceived notions. The concept that pathogenic germs cause infections generating an innate immune response (e.g., Aβ and tau produced by peripheral organs) that is associated with incident dementia is worthwhile considering in the context of sporadic AD with an unknown root cause. Therefore, the peripheral amyloid hypothesis to cognitive impairment and AD is proposed and remains to be vetted by future research. Meanwhile, humans remain complex variable organisms with individual risk factors that define their immune status, neurovascular function, and neuronal plasticity. In this focused review, the idea that infections and organ dysfunction contribute to Alzheimer’s disease, through the generation of peripheral amyloids and/or neurovascular unit dysfunction will be explored and discussed. Ultimately, many questions remain to be answered and critical areas of future exploration are highlighted.

Using the Alzheimer's Disease Neuroimaging Initiative to improve early detection, diagnosis, and treatment of Alzheimer's disease

INTRODUCTION

The Alzheimer's Disease Neuroimaging Initiative (ADNI) has accumulated 15 years of clinical, neuroimaging, cognitive, biofluid biomarker and genetic data, and biofluid samples available to researchers, resulting in more than 3500 publications. This review covers studies from 2018 to 2020.

METHODS

We identified 1442 publications using ADNI data by conventional search methods and selected impactful studies for inclusion.

RESULTS

Disease progression studies supported pivotal roles for regional amyloid beta (Aβ) and tau deposition, and identified underlying genetic contributions to Alzheimer's disease (AD). Vascular disease, immune response, inflammation, resilience, and sex modulated disease course. Biologically coherent subgroups were identified at all clinical stages. Practical algorithms and methodological changes improved determination of Aβ status. Plasma Aβ, phosphorylated tau181, and neurofilament light were promising noninvasive biomarkers. Prognostic and diagnostic models were externally validated in ADNI but studies are limited by lack of ethnocultural cohort diversity.

DISCUSSION

ADNI has had a profound impact in improving clinical trials for AD.

Associations of Stages of Objective Memory Impairment With Amyloid PET and Structural MRI: The A4 Study

BACKGROUND AND OBJECTIVES

The goal of this work was to investigate the neuroimaging correlates of the Stages of Objective Memory Impairment (SOMI) system operationalized with the Free and Cued Selective Reminding Test (FCSRT), a widely used episodic memory measure.

METHODS

The FCSRT begins with a study phase in which items (e.g., grapes) are identified in response to unique semantic cues (e.g., fruit) that are used in the test phase to prompt recall of items not retrieved by free recall. There are 3 test trials of the 16 items (maximum 48). Data from 4,484 cognitively unimpaired participants from the Anti-Amyloid Treatment in Asymptomatic Alzheimer's (A4) study were used. All participants had amyloid PET imaging, and a subset of 1,262 β-amyloid (Aβ)-positive had structural MRIs. We compared the Aβ mean cortical standardized uptake value ratio (SUVR) and volumetric measures of hippocampus, parahippocampal gyrus, entorhinal cortex, and inferior temporal cortex between the 5 SOMI stages.

RESULTS

Participants had a mean age of 71.3 (SD 4.6) years; 40.6% were male; and 34.6% were APOE ε4 positive. Half had no memory impairment; the other half had retrieval deficits, storage limitations, or both. Analysis of covariance in the entire sample while controlling for age, sex, education, and APOE ε4 showed that individuals in higher SOMI stages had higher global amyloid SUVR (p < 0.001). Both SOMI-4 and -3 subgroups had higher amyloid SUVR than SOMI-0 and SOMI-1 subgroups. Individuals in higher SOMI stages had smaller hippocampal volume (p = 0.003), entorhinal cortex (p < 0.05), and inferior temporal lobes (p < 0.05), but there was no difference between parahippocampal gyrus volume of different SOMI stages. Pairwise comparison of SOMI subgroups showed that the SOMI-4, -3, and -2 subgroups had smaller hippocampal volume than the SOMI-0 and -1 subgroup. The SOMI-4 subgroup had significantly smaller entorhinal cortex and smaller inferior temporal lobe compared to all other groups.

DISCUSSION

Presence of Alzheimer disease pathology is closely related to memory impairment according to SOMI stages in the cognitively unimpaired sample of A4. Results from structural MRIs suggest that memory storage impairment (SOMI-3 and -4) is present when there is widespread medial temporal lobe atrophy.

TRIAL REGISTRATION INFORMATION

ClinicalTrials.gov identifier: NCT02008357.

CLASSIFICATION OF EVIDENCE

This study provides Class I evidence that, in normal older individuals, higher stages of memory impairment assessed with FCSRT were associated with higher amyloid imaging burden and lower volume of hippocampus, entorhinal cortex, and inferior temporal lobes.

Non-linear Character of Plasma Amyloid Beta Over the Course of Cognitive Decline in Alzheimer’s Continuum

Plasma amyloid-β (Aβ) was associated with brain Aβ deposition and Alzheimer’s disease (AD) development. However, changes of plasma Aβ over the course of cognitive decline in the Alzheimer’s continuum remained uncertain. We recruited 449 participants to this study, including normal controls (NC), subjective cognitive decline (SCD), mild cognitive impairment (MCI), AD, and non-AD dementia. All the participants underwent plasma Aβ42, Aβ40, and t-tau measurements with single-molecule array (Simoa) immunoassay and PET scan with 18F-florbetapir amyloid tracer. In the subgroup of Aβ-PET positive, plasma Aβ42 and Aβ42/Aβ40 ratio was significantly lower in AD than NC, SCD and MCI, yet SCD had significantly higher levels of plasma Aβ42 than both NC and MCI. In the diagnostic groups of MCI and dementia, participants with Aβ-PET positive had lower plasma Aβ42 and Aβ42/40 ratio than participants with Aβ-PET negative, and the increasing levels of plasma Aβ42 and Aβ42/40 ratio indicated lower risks of Aβ-PET positive. However, in the participants with SCD, plasma Aβ42 and Aβ40 were higher in the subgroup of Aβ-PET positive than Aβ-PET negative, and the increasing levels of plasma Aβ42 and Aβ40 indicated higher risks of Aβ-PET positive. No significant association was observed between plasma Aβ and Aβ-PET status in normal controls. These findings showed that, in the continuum of AD, plasma Aβ42 had a significantly increasing trend from NC to SCD before decreasing in MCI and AD. Furthermore, the predictive values of plasma Aβ for brain amyloid deposition were inconsistent over the course of cognitive decline.