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  • 1
    In: Alzheimer's & Dementia: Translational Research & Clinical Interventions, Wiley, Vol. 9, No. 1 ( 2023-01)
    Abstract: The positron emission tomography (PET) radiotracer [ 18 F]MK‐6240 exhibits high specificity for neurofibrillary tangles (NFTs) of tau protein in Alzheimer's disease (AD), high sensitivity to medial temporal and neocortical NFTs, and low within‐brain background. Objectives were to develop and validate a reproducible, clinically relevant visual read method supporting [ 18 F]MK‐6240 use to identify and stage AD subjects versus non‐AD and controls. Methods Five expert readers used their own methods to assess 30 scans of mixed diagnosis (47% cognitively normal, 23% mild cognitive impairment, 20% AD, 10% traumatic brain injury) and provided input regarding regional and global positivity, features influencing assessment, confidence, practicality, and clinical relevance. Inter‐reader agreement and concordance with quantitative values were evaluated to confirm that regions could be read reliably. Guided by input regarding clinical applicability and practicality, read classifications were defined. The readers read the scans using the new classifications, establishing by majority agreement a gold standard read for those scans. Two naïve readers were trained and read the 30‐scan set, providing initial validation. Inter‐rater agreement was further tested by two trained independent readers in 131 scans. One of these readers used the same method to read a full, diverse database of 1842 scans; relationships between read classification, clinical diagnosis, and amyloid status as available were assessed. Results Four visual read classifications were determined: no uptake, medial temporal lobe (MTL) only, MTL and neocortical uptake, and uptake outside MTL. Inter‐rater kappas were 1.0 for the naïve readers gold standard scans read and 0.98 for the independent readers 131‐scan read. All scans in the full database could be classified; classification frequencies were concordant with NFT histopathology literature. Discussion This four‐class [ 18 F]MK‐6240 visual read method captures the presence of medial temporal signal, neocortical expansion associated with disease progression, and atypical distributions that may reflect different phenotypes. The method demonstrates excellent trainability, reproducibility, and clinical relevance supporting clinical use. Highlights A visual read method has been developed for [ 18 F]MK‐6240 tau positron emission tomography. The method is readily trainable and reproducible, with inter‐rater kappas of 0.98. The read method has been applied to a diverse set of 1842 [ 18 F]MK‐6240 scans. All scans from a spectrum of disease states and acquisitions could be classified. Read classifications are consistent with histopathological neurofibrillary tangle staging literature.
    Type of Medium: Online Resource
    ISSN: 2352-8737 , 2352-8737
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 2832891-7
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  • 2
    In: Alzheimer's & Dementia, Wiley, Vol. 18, No. S6 ( 2022-12)
    Abstract: Ethno‐racial factors may influence the multifactorial etiology and heterogeneity of Alzheimer Disease (AD). Given the conflicting reports on racial differences in AD, well‐powered cohort studies are needed to identify differences in AD biomarkers between racialized groups. Method This NIH‐funded study aims to determine cross‐sectional and longitudinal differences in AD biomarkers between self‐reported Black/African Americans (AA) and non‐Hispanic Whites. It implements a longitudinal design with centralized and standardized analyses of cerebrospinal fluid (CSF) and plasma samples, MRI and amyloid and tau PET scans, and harmonized clinical/cognitive outcomes. It leverages available retrospective biofluid samples and brain scans, and prospectively collected data from four ADRCs (Washington University (WU), University of Pennsylvania, Emory University, University of Alabama), and the study of African Americans Fighting Alzhiemer’s in Midlife (AA‐FAIM)), in addition to the derived data from the Harvard Aging Brain Study and the Anti‐Amyloid Treatment in Asymptomatic Alzheimer’s (A4) trial. It will further determine the roles of major risk factors and Social and Structural Determinants Influencing Aging and Dementia (SS‐DIAD) in racial differences. Results By 12/31/2021, ∼3114 CSF samples, 4896 MRI scans, 3754 amyloid PET scans, and 998 tau PET scans retrospectively collected across studies were transferred to WU Knight ADRC Fluid Biomarker and Imaging Cores. CSF Aβ42, Aβ40, Tau, pTau181, and NfL were measured from all CSF samples. A subset of 3687 MRI scans and 2336 amyloid PET scans were re‐processed. Preliminary analyses on data from 179 AAs and 1180 Whites (all CDR 0 at baseline) indicated that baseline CSF Tau and pTau181 were lower, and Aβ42/Aβ40 was higher, in AAs compared to Whites. Longitudinally, CSF Aβ42/Aβ40 declined more slowly, and amyloid (PET) uptake and CSF Tau (pTau181) increased more slowly, in AAs than Whites. Additionally, a multi‐domain battery of SS‐DIAD was pilot tested, and revealed high test‐retest intraclass correlations (ICC 〉 =0.83) for multiple domains, facilitating a uniform collection of SS‐DIAD across sites. Conclusion It is feasible to harmonize biomarker data and SS‐DIAD across multiple studies to understand cross‐sectional and longitudinal ethno‐racial differences in AD. Preliminary analyses suggest cross‐sectional and longitudinal differences in both amyloid and tau biomarkers between self‐reported AA and Whites.
    Type of Medium: Online Resource
    ISSN: 1552-5260 , 1552-5279
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2022
    detail.hit.zdb_id: 2201940-6
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  • 3
    In: Alzheimer's & Dementia, Wiley, Vol. 18, No. 8 ( 2022-08), p. 1545-1564
    Abstract: Black Americans are disproportionately affected by dementia. To expand our understanding of mechanisms of this disparity, we look to Alzheimer's disease (AD) biomarkers. In this review, we summarize current data, comparing the few studies presenting these findings. Further, we contextualize the data using two influential frameworks: the National Institute on Aging–Alzheimer's Association (NIA‐AA) Research Framework and NIA's Health Disparities Research Framework. The NIA‐AA Research Framework provides a biological definition of AD that can be measured in vivo. However, current cut‐points for determining pathological versus non‐pathological status were developed using predominantly White cohorts—a serious limitation. The NIA's Health Disparities Research Framework is used to contextualize findings from studies identifying racial differences in biomarker levels, because studying biomakers in isolation cannot explain or reduce inequities. We offer recommendations to expand study beyond initial reports of racial differences. Specifically, life course experiences associated with racialization and commonly used study enrollment practices may better account for observations than exclusively biological explanations.
    Type of Medium: Online Resource
    ISSN: 1552-5260 , 1552-5279
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2022
    detail.hit.zdb_id: 2201940-6
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  • 4
    In: Alzheimer's & Dementia, Wiley, Vol. 18, No. S5 ( 2022-12)
    Abstract: In an emerging biomarker era, scientists, clinicians and patients must trust that Alzheimer’s disease (AD) biomarkers are broadly applicable across populations. However, biomarker studies inadequately include minoritized populations – largely because biomarker collection is invasive and centralized, and outreach wholly insufficient. The AA‐FAIM study collected plasma and cognitive data from a Black cohort by leveraging existing resources from the Wisconsin Alzheimer’s Disease Research Center and Wisconsin Registry for Alzheimer’s Prevention. We compared two easily‐decentralized and low‐burden options for measuring preclinical changes–either alone or combined, testing associations of baseline plasma Aβ42/40 and intra‐individual cognitive variability (IICV) with longitudinal cognition. Methods Using AA‐FAIM participants’ cognitive data, we derived an estimate of baseline IICV from z‐scores, representing standard deviation across five indices from list learning, executive function, and confrontational naming tests. PrecivityAD TM assays quantified baseline plasma Aβ42/40. After comparing baseline IICV associations for factor‐validity (Figure 1), we conducted linear mixed‐effects models examining associations of baseline plasma Aβ42/40, IICV, or the combination of markers with longitudinal cognition on eight outcomes. Fully adjusted models included age‐at‐assessment, gender, education, and random intercepts. Benjamini‐Hochberg (BH) corrections controlling false discovery rate at 5% were applied across outcomes. Using Bayesian Information Criterion (BIC), plasma Aβ42/40 models were assessed for comparative fits with and without IICV interactions and main effects. Results Models included between 163‐667 observations from 56‐174 participants (Table 1). In models without plasma, IICV * age was weakly significant only for Trails tests with higher baseline IICV being associated with worse trajectories (Table 2; uncorrected/corrected p‐values=0.057/0.227 (log Trails A) and 0.044/0.227 (log Trails B)). Plasma Aβ42/40 was significantly associated with trajectories across multiple cognitive outcomes regardless of IICV inclusion (Table 3). Model estimates suggested lower baseline Aβ42/40 was associated with worse performance over time (Figures 2‐3). All interactions survived correction with IICV in the model. Without IICV, only Trails B survived correction. BIC comparisons suggested removing the IICV * age interaction from plasma models, but retaining IICV main effects. Conclusions Baseline plasma Aβ42/40 predicted cognitive trajectory in a Black cohort. Although IICV appeared less sensitive than plasma Aβ42/40 in moderating cognitive trajectory, models including both IICV and plasma Aβ42/40 may be better in predicting trajectories.
    Type of Medium: Online Resource
    ISSN: 1552-5260 , 1552-5279
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2022
    detail.hit.zdb_id: 2201940-6
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  • 5
    In: Alzheimer's & Dementia, Wiley, Vol. 14, No. 7S_Part_9 ( 2018-07)
    Type of Medium: Online Resource
    ISSN: 1552-5260 , 1552-5279
    Language: English
    Publisher: Wiley
    Publication Date: 2018
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  • 6
    In: Alzheimer's & Dementia, Wiley, Vol. 16, No. S3 ( 2020-12)
    Abstract: Amyloidosis in Alzheimer’s disease (AD) is a common feature that can be measured via cerebrospinal fluid (CSF), positron emission tomography (PET), and autopsy measures of neuritic plaques. While individual genome‐wide association studies (GWAS) have identified more than 40 loci as potential biological drivers of AD, fewer drivers of amyloidosis have been identified due to the small sample sizes in endophenotype analyses. Combining unimodal measures of amyloid into a larger multi‐modal analysis could provide new insight into mechanisms driving amyloidosis. The goal of this study was to conduct a large meta‐analysis of CSF‐, PET‐, and pathology‐derived metrics of amyloid positivity. Method 11,941 non‐Hispanic white participants (CSF = 2505, PET = 3976, Autopsy = 5460) from 14 cohorts were analyzed. To facilitate cross‐modality harmonization, a binarized amyloid status (negative/positive) was determined on an individual cohort basis using two approaches: a Gaussian mixture model clustering algorithm for CSF/PET measurements and CERAD thresholds (CERAD 〉 sparse or CERAD ≤ sparse) for autopsy measures of amyloid pathology. In total, our analysis included 5,634 amyloid‐negative and 6,307 amyloid‐positive individuals. GWAS using a logistic regression model covarying for age and sex were performed in each of the 14 cohorts, and a meta‐analysis was performed within each modality. These meta‐analyses were followed with a multi‐modal meta‐analysis. The standard genome‐wide threshold of statistical significance (p  〈  5 × 10 −8 ) was applied. Additionally, we performed candidate analysis for the 39 previously published clinical AD or amyloid risk loci. Result Aside from variants within the APOE region, our multi‐modal meta‐analysis did not identify any genome‐wide loci (Figure 1). A lack of convergent GWAS signals was also observed when stratifying by age, sex, and APOE carrier status. However, our candidate gene analysis demonstrated some consistency across modalities. Two prior loci were significant in 2/3 modalities, including ABCA7 (rs4147929; p = 1.98 × 10 −4 ) and CLU (rs4236671; p = 0.001). Conclusion In the largest GWAS of brain amyloidosis, we found a lack of convergence across modalities, suggesting substantial heterogeneity across measures and cohorts. Candidate analyses highlight some consistent signals in ABCA7 and CLU . Results suggest continued emphasis on increasing sample sizes for endophenotype analyses and on standardized methodologies to reduce sample heterogeneity to improve statistical power.
    Type of Medium: Online Resource
    ISSN: 1552-5260 , 1552-5279
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2020
    detail.hit.zdb_id: 2201940-6
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  • 7
    In: Alzheimer's & Dementia, Wiley, Vol. 16, No. S5 ( 2020-12)
    Abstract: Reduced cerebral blood flow (CBF) has been considered as a potentially early biomarker of late‐onset Alzheimer’s disease (AD). We sought to detect the pattern of age‐related CBF trajectories, and to investigate how these trajectories are affected by APOE , chromosomal sex, and cardiometabolic measurements. Method From two ongoing longitudinal cohort studies—the Wisconsin Registry for Alzheimer's Prevention and the Wisconsin Alzheimer’s Disease Research Center—we included 950 individuals (age range 40—89 years), who were cognitively unimpaired at their first visit. CBF was measured using pseudo‐continuous arterial spin labeling MRI. Demographic factors, APOE ɛ4 status, and cardiometabolic measurements were obtained during a clinic visit that included structured interviews, physical examinations, and blood sampling. We applied linear mixed‐effects models in our analyses, which focused on brain regions of relevance to AD. Result During the follow‐up period (median 2.17 years, range 0.13—8.24 years), increasing age was significantly associated with decreasing CBF in total gray matter (β=‐1.54) (Figure, a), hippocampus (‐1.33), superior frontal gyrus (‐1.92), middle frontal gyrus (‐2.20), posterior cingulate (‐2.71), and precuneus (‐2.32), with all p‐values 〈 0.01. A three‐way interactive effect of age, sex, and APOE ɛ4 allele was observed on CBF trajectories. That is, compared with male ɛ4 carriers, female ɛ4 carriers showed a faster decline in global and regional CBF with increasing age (Figure, c), whereas age‐related decline in CBF was similar between male and female ɛ4 non‐carriers (Figure, b). Worse cardiometabolic profile (i.e., increased systolic blood pressure, body mass index, total cholesterol, and blood glucose) was associated with lower CBF at all the visits. When time‐varying cardiometabolic measurements were adjusted in the model, the synergistic effect of sex and APOE ɛ4 on age‐related CBF trajectories became largely attenuated. Conclusion Our findings demonstrate that APOE genotype and sex interactively impact CBF trajectories across the lifespan, and that this effect may be partially explained by cardiometabolic alterations.
    Type of Medium: Online Resource
    ISSN: 1552-5260 , 1552-5279
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2020
    detail.hit.zdb_id: 2201940-6
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  • 8
    In: Alzheimer's & Dementia, Wiley, Vol. 16, No. S3 ( 2020-12)
    Abstract: Genetic studies of Alzheimer’s disease (AD) have focused on the clinical or pathological diagnosis as the primary outcome, but little is known about the genetic basis of the preclinical phase of the disease. Our goal was to identify the underlying genetic bases for brain amyloidosis during the preclinical phase of AD. Method We performed genome‐wide association studies of positron emission tomography (PET) amyloid levels and meta‐analyzed the results. Genetic and imaging data were acquired from ten cohorts of primarily non‐demented individuals. The largest cohort, the A4 study (n = 3,154) was a secondary prevention trial designed to slow cognitive decline associated with brain amyloidosis. The other, smaller longitudinal cohort studies, similar in design, provided additional amyloid PET data with existing genetic data (n = 1,160 analyzed and n = 550 currently being analyzed). Result We identified a locus for amyloidosis within RBFOX1 in addition to APOE along with several loci nearing significance. Conclusion Multiple genetic loci may be associated with brain amyloidosis. Further research into these specific loci and genes will help in our understanding of the molecular bases of amyloid buildup in the brain.
    Type of Medium: Online Resource
    ISSN: 1552-5260 , 1552-5279
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2020
    detail.hit.zdb_id: 2201940-6
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  • 9
    In: Alzheimer's & Dementia, Wiley, Vol. 16, No. S1 ( 2020-12)
    Abstract: Understanding cerebrovascular health in Alzheimer’s disease (AD) is vital, as the majority of individuals with dementia due to AD are also found to have vascular disease at autopsy. We examined the relationships between centrally and peripherally measured vascular health markers and amyloid accumulation across the AD clinical spectrum. Method Cerebral white matter (WM) disease was determined by a neuroradiologist using the Cardiovascular Health Study (CHS) score in 236 individuals (75% cognitively healthy, 25% cognitively impaired; Table 1) from the Wisconsin ADRC and WRAP cohorts. A subset (n = 73) of individuals completed [C‐11]PiB PET imaging. Metrics of internal carotid arterial (ICA) health assessed by 4D‐flow MRI as well as WM hyperintensity lesion volume (WMH‐LV), amyloid accumulation, vascular risk factors, and cognitive status were examined across individuals with high (≥3) and low ( 〈 3) CHS scores (Table 2, Figures 1 & 2). A threshold for vascular positivity (V+/‐) was identified as 1.5SD 〉 the mean %WMH‐LV of total intracranial volume in individuals with CHS 〈 3. Participants were classified according to their amyloid and vascular positivity status. Result In the larger dataset (n = 236), individuals with CHS≥3 were significantly older, more likely to be cognitively impaired, and demonstrated higher pulse pressure, lower cholesterol, and greater %WMH‐LV (Table 1, Figure 1). There was no difference between CHS groups in average ICA blood flow, ICA pulse wave velocity, or global PiB accumulation (Table 2). Neither CHS rating nor %WMH‐LV were associated with amyloid (Spearman’s rho = ‐.128, p = .280; Spearman’s rho = .078, p = .511, respectively). When using %WMH‐LV as a biomarker for cerebrovascular health, the vascular positivity threshold was 0.409%. In individuals with amyloid imaging, 54.8%(38/73) were V‐/A‐, 8.2%(8/73) were V+/A‐, 34.2%(24/73) were V‐/A+, and (2/73)0.8% were V+/A+. CHS rating and vascular positivity were not related to cognitive diagnosis in the amyloid imaging subset (Figure 2). Conclusion Elevated cerebral WM disease (CHS≥3) was related to greater WMH lesion burden, but not blood flow or pulse wave velocity of the ICAs. Thus far, in this sample spanning the continuum of AD, neuroimaging measures of vascular health were not related to amyloid, suggesting independence of these pathologies. Investigations into the associations between amyloid, cerebrovascular health, and cognition are ongoing as more data become available.
    Type of Medium: Online Resource
    ISSN: 1552-5260 , 1552-5279
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2020
    detail.hit.zdb_id: 2201940-6
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  • 10
    In: Alzheimer's & Dementia, Wiley, Vol. 17, No. S1 ( 2021-12)
    Abstract: Cerebrovascular disease (CVD), has been linked with dementia stages of Alzheimer’s disease (AD); however, the question of whether CVD is associated with underlying AD pathophysiology remains unresolved. This work investigated the relationship between advanced MRI based cerebrovascular markers with AD biomarkers of β‐amyloid deposition and neurofibrillary tau tangles in subjects spanning the AD clinical spectrum. Method Subjects: Study groups are summarized in figure 1. MRI: Whole brain 4D‐Flow data were acquired on a 3.0T system using a 32‐channel head coil. From 4D‐Flow images, intracranial blood flow, trans‐capillary pulse wave delay, and low frequency oscillations (LFOs) were estimated. Trans‐capillary pulse wave delay was defined as the cardiac pulse wave transit time from intracranial arteries‐to‐capillaries‐to‐veins and was measured from cardiac wave time‐to‐upstroke differences in arteries and veins. White matter hyperintensity (WMH) lesion volumes were segmented from T2‐FLAIR images using the Lesion Segmentation Toolbox in SPM12. PET: Four groups were established based on clinical diagnosis and biomarker positivity. Subjects were classified as cognitively normal (CN) or impaired (IM) (MCI or dementia) based on a clinical consensus review. Amyloid (A) (+/‐) was determined using a previously established global PiB DVR threshold 〉 1.19 and tau (T) (+/‐) was determined using a previously established entorhinal cortex MK‐6240 SUVR threshold 〉 1.27. Pairwise statistical differences were assessed using ANOVA followed by post‐hoc analysis (P 〈 0.05 significance). Result Trans‐capillary pulse wave delay was significantly longer in controls (A‐/T‐/CN) when compared with AD biomarker confirmed groups (fig 2 b) (P 〈 0.001). Low frequency flow range and LFOs were significantly lower and diminished in A+T+ groups both cognitively normal and impaired (fig 3 P 〈 0.001; fig 4 P=0.027, P=0.046, P=0.046). Linear regression analysis showed a weak correlation between trans‐capillary pulse wave delay and PiB and MK‐6240 (R 2 =0.12, R 2 =0.04), and between LFOs and PiB and MK‐6240 (R 2 =0.07, R 2 =0.03) (fig 5). No significant AT biomarker group differences were observed across other modalities such as traditional cardiovascular and cerebrovascular metrics, including WMH lesion volumes (fig 1). Conclusion Although more traditional measures of CVD were not related to biomarker groups, 4D‐Flow MRI based vascular markers suggest significant intracranial vascular stiffness and reduced autoregulation‐related vasomotion in AD biomarker positive subjects during preclinical AD.
    Type of Medium: Online Resource
    ISSN: 1552-5260 , 1552-5279
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 2201940-6
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