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Association of Amyloid and Tau With Cognition in Preclinical Alzheimer Disease: A Longitudinal Study.

ABSTRACT: Importance:Positron emission tomography (PET) imaging now allows in vivo visualization of both neuropathologic hallmarks of Alzheimer disease (AD): amyloid-? (A?) plaques and tau neurofibrillary tangles. Observing their progressive accumulation in the brains of clinically normal older adults is critically important to understand the pathophysiologic cascade leading to AD and to inform the choice of outcome measures in prevention trials. Objective:To assess the associations among A?, tau, and cognition, measured during different observation periods for 7 years. Design, Setting, and Participants:Prospective cohort study conducted between 2010 and 2017 at the Harvard Aging Brain Study, Boston, Massachusetts. The study enrolled 279 clinically normal participants. An additional 90 individuals were approached but declined the study or did not meet the inclusion criteria. In this report, we analyzed data from 60 participants who had multiple A? and tau PET observations available on October 31, 2017. Main Outcomes and Measures:A median of 3 Pittsburgh compound B-PET (A?, 2010-2017) and 2 flortaucipir-PET (tau, 2013-2017) images were collected. We used initial PET and slope data, assessing the rates of change in A? and tau, to measure cognitive changes. Cognition was evaluated annually using the Preclinical Alzheimer Cognitive Composite (2010-2017). Annual consensus meetings evaluated progression to mild cognitive impairment. Results:Of the 60 participants, 35 were women (58%) and 25 were men (42%); median age at inclusion was 73 years (range, 65-85 years). Seventeen participants (28%) exhibited an initial high A? burden. An antecedent rise in A? was associated with subsequent changes in tau (1.07 flortaucipir standardized uptake value ratios [SUVr]/PiB-SUVr; 95% CI, 0.13-3.46; P?=?.02). Tau changes were associated with cognitive changes (-3.28 z scores/SUVR; 95% CI, -6.67 to -0.91; P?=?.001), covarying baseline A? and tau. Tau changes were greater in the participants who progressed to mild cognitive impairment (n?=?6) than in those who did not (n?=?11; 0.05 SUVr per year; 95% CI, 0.03-0.07; P?=?.001). A serial mediation model demonstrated that the association between initial A? and final cognition, measured 7 years later, was mediated by successive changes in A? and tau. Conclusions and Relevance:We identified sequential changes in normal older adults, from A? to tau to cognition, after which the participants with high A? with greater tau increase met clinical criteria for mild cognitive impairment. These findings highlight the importance of repeated tau-PET observations to track disease progression and the importance of repeated amyloid-PET observations to detect the earliest AD pathologic changes.

SUBMITTER: Hanseeuw BJ

PROVIDER: S-EPMC6547132 | biostudies-literature | 2019 Jun

REPOSITORIES: biostudies-literature

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Association of Amyloid and Tau With Cognition in Preclinical Alzheimer Disease: A Longitudinal Study.

Hanseeuw Bernard J BJ Betensky Rebecca A RA Jacobs Heidi I L HIL Schultz Aaron P AP Sepulcre Jorge J Becker J Alex JA Cosio Danielle M Orozco DMO Farrell Michelle M Quiroz Yakeel T YT Mormino Elizabeth C EC Buckley Rachel F RF Papp Kathryn V KV Amariglio Rebecca A RA Dewachter Ilse I Ivanoiu Adrian A Huijbers Willem W Hedden Trey T Marshall Gad A GA Chhatwal Jasmeer P JP Rentz Dorene M DM Sperling Reisa A RA Johnson Keith K

JAMA neurology 20190801 8

<h4>Importance</h4>Positron emission tomography (PET) imaging now allows in vivo visualization of both neuropathologic hallmarks of Alzheimer disease (AD): amyloid-β (Aβ) plaques and tau neurofibrillary tangles. Observing their progressive accumulation in the brains of clinically normal older adults is critically important to understand the pathophysiologic cascade leading to AD and to inform the choice of outcome measures in prevention trials.<h4>Objective</h4>To assess the associations among A ...[more]

PMID: 31157827

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Project description:Importance:The accumulation of aggregated ?-amyloid and tau proteins into plaques and tangles is a central feature of Alzheimer disease (AD). While plaque and tangle accumulation likely contributes to neuron and synapse loss, disease-related changes to oligodendrocytes and myelin are also suspected of playing a role in development of AD dementia. Still, to our knowledge, little is known about AD-related myelin changes, and even when present, they are often regarded as secondary to concomitant arteriosclerosis or related to aging. Objective:To assess associations between hallmark AD pathology and novel quantitative neuroimaging markers while being sensitive to white matter myelin content. Design, Setting, and Participants:Magnetic resonance imaging was performed at an academic research neuroimaging center on a cohort of 71 cognitively asymptomatic adults enriched for AD risk. Lumbar punctures were performed and assayed for cerebrospinal fluid (CSF) biomarkers of AD pathology, including ?-amyloid 42, total tau protein, phosphorylated tau 181, and soluble amyloid precursor protein. We measured whole-brain longitudinal and transverse relaxation rates as well as the myelin water fraction from each of these individuals. Main Outcomes and Measures:Automated brain mapping algorithms and statistical models were used to evaluate the relationships between age, CSF biomarkers of AD pathology, and quantitative magnetic resonance imaging relaxometry measures, including the longitudinal and transverse relaxation rates and the myelin water fraction. Results:The mean (SD) age for the 19 male participants and 52 female participants in the study was 61.6 (6.4) years. Widespread age-related changes to myelin were observed across the brain, particularly in late myelinating brain regions such as frontal white matter and the genu of the corpus callosum. Quantitative relaxometry measures were negatively associated with levels of CSF biomarkers across brain white matter and in areas preferentially affected in AD. Furthermore, significant age-by-biomarker interactions were observed between myelin water fraction and phosphorylated tau 181/?-amyloid 42, suggesting that phosphorylated tau 181/?-amyloid 42 levels modulate age-related changes in myelin water fraction. Conclusions and Relevance:These findings suggest amyloid pathologies significantly influence white matter and that these abnormalities may signify an early feature of the disease process. We expect that clarifying the nature of myelin damage in preclinical AD may be informative on the disease's course and lead to new markers of efficacy for prevention and treatment trials.

Project description:Importance:It is critically important to improve our ability to diagnose and track Alzheimer disease (AD) as early as possible. Individuals with autosomal dominant forms of AD can provide clues as to which and when biological changes are reliably present prior to the onset of clinical symptoms. Objective:To characterize the associations between amyloid and tau deposits in the brains of cognitively unimpaired and impaired carriers of presenilin 1 (PSEN1) E280A mutation. Design, Setting, and Participants:In this cross-sectional imaging study, we leveraged data from a homogeneous autosomal dominant AD kindred, which allowed us to examine measurable tau deposition as a function of individuals' proximity to the expected onset of dementia. Cross-sectional measures of carbon 11-labeled Pittsburgh Compound B positron emission tomography (PET) and flortaucipir F 18 (previously known as AV 1451, T807) PET imaging were assessed in 24 PSEN1 E280A kindred members (age range, 28-55 years), including 12 carriers, 9 of whom were cognitively unimpaired and 3 of whom had mild cognitive impairment, and 12 cognitively unimpaired noncarriers. Main Outcomes and Measures:We compared carbon 11-labeled Pittsburgh Compound B PET cerebral with cerebellar distribution volume ratios as well as flortaucipir F 18 PET cerebral with cerebellar standardized uptake value ratios in mutation carriers and noncarriers. Spearman correlations characterized the associations between age and mean cortical Pittsburgh Compound B distribution volume ratio levels or regional flortaucipir standardized uptake value ratio levels in both groups. Results:Of the 24 individuals, the mean (SD) age was 38.0 (7.4) years, or approximately 6 years younger than the expected onset of clinical symptoms in carriers. Compared with noncarriers, cognitively unimpaired mutation carriers had elevated mean cortical Pittsburgh Compound B distribution volume ratio levels in their late 20s, and 7 of 9 carriers older than 30 years reached the threshold for amyloidosis (distribution volume ratio level?>?1.2). Elevated levels of tau deposition were seen within medial temporal lobe regions in amyloid-positive mutation carriers 6 years before clinical onset of AD in this kindred. Substantial tau deposition in the neocortex was only observed in 1 unimpaired carrier and in those with mild cognitive impairment. ?-Amyloid uptake levels were diffusely elevated in unimpaired carriers approximately 15 years prior to expected onset of mild cognitive impairment. In carriers, higher levels of tau deposition were associated with worse performance on the Mini-Mental State Examination (entorhinal cortex: r?=?-0.60; P?=?.04; inferior temporal lobe: r?=?-0.54; P?=?.06) and the Consortium to Establish a Registry for Alzheimer Disease Word List Delayed Recall (entorhinal cortex: r?=?-0.86; P?<?.001; inferior temporal lobe: r?=?-0.70; P?=?.01). Conclusions and Relevance:The present findings add to the growing evidence that molecular markers can characterize biological changes associated with AD in individuals who are still cognitively unimpaired. The findings also suggest that tau PET imaging may be useful as a biomarker to distinguish individuals at high risk to develop the clinical symptoms of AD and to track disease progression.

Project description:Importance:Older age, high levels of ?-amyloid (A?), and the presence of the apolipoprotein E (APOE) ?4 allele are risk factors for Alzheimer disease (AD). However, the extent to which increasing age, A?, and ?4 are associated with memory decline remains unclear, and the age at which memory decline begins for A?-positive ?4 carriers and noncarriers has not been determined. Objective:To determine the association of age, A? level, and APOE ?4 with memory decline in a large group of cognitively healthy older adults. Design, Setting, and Participants:This longitudinal observational study included cognitively healthy older adults (age >60 years) enrolled in the Australian Imaging, Biomarkers and Lifestyle (AIBL) study from March 31, 2006, through March 31, 2017; of 1583 individuals enrolled, 1136 refused or were excluded owing to other criteria (eg, having mild cognitive impairment or AD). Participants underwent A? imaging in research clinics in Perth and Melbourne and more than 72 months of follow-up (at 18-month intervals). The association of age with memory was fitted to a quadratic model. Age was treated as a continuous, time-dependent variable. Exposures:?-Amyloid imaging using positron emission tomography, genotyping for APOE ?4, and longitudinal neuropsychological assessments of episodic memory during the 72-month follow-up. Main Outcomes and Measures:Episodic memory composite score. Results:Of the 447 participants, 203 (45.4%) were men and 244 (54.6%) were women; mean (SD) age was 72.5 (6.6) years. Equal proportions of female participants were observed in each A?-?4 group (24 of 51 A?-positive ?4 noncarriers [47.1%] ; 35 of 64 A?-negative ?4 carriers [54.7%]; 40 of 72 A?-positive ?4 carriers [55.6%]; and 145 of 260 A?-negative ?4 noncarriers [55.8%]). Adults with A? findings (mean [SD] age, 74.4 [6.8] years) were approximately 4 years older than those negative for A? (mean [SD] age, 69.8 [6.1] years). Memory decline diverged significantly from A?-negative ?4 noncarriers at an earlier age in A?-positive ?4 carriers (64.5 years) than in A?-positive ?4 noncarriers (76.5 years), such that by 85 years of age, A?-positive ?4 carriers performed approximately 1.5 SD units worse on the episodic memory composite than A?-negative ?4 noncarriers and approximately 0.8 SD units worse than A?-positive ?4 noncarriers. Memory performance of A?-negative ?4 carriers did not differ from that of the A?-negative ?4 noncarriers (estimate [SE], 0.001 [0.001]; t?=?0.526; P?=?.77). Conclusions and Relevance:Prior work has shown that A? and ?4 combine to influence memory decline in nondemented older adults. Results of this study indicate that increasing age may further exacerbate these effects. The estimates provided may be used to determine the risk of memory decline associated with A? and ?4 at each age.

Project description:Clinical trials testing treatments for Alzheimer disease (AD) are increasingly focused on cognitively normal individuals in the preclinical phase of the disease. To optimize observing a treatment effect, such trials need to enroll cognitively normal individuals likely to show cognitive decline over the duration of the trial.To identify which group of cognitively normal individuals shows the greatest cognitive decline over time based on their cerebrospinal fluid biomarker profile.In this cohort study, cognitively normal participants were classified into 1 of the following 4 hypothetical preclinical AD groups using baseline cerebrospinal fluid levels of A? and tau or A? and phosphorylated tau (p-tau): stage 0 (high A? and low tau), stage 1 (low A? and low tau), stage 2 (low A? and high tau), and suspected non-AD pathology (SNAP) (high A? and high tau). The data presented herein were collected between August 1995 and August 2014.An a priori cognitive composite score based on the following 4 tests previously shown to predict progression from normal cognition to symptom onset of mild cognitive impairment or dementia: Paired Associates immediate recall, Logical Memory delayed recall, Boston Naming, and Digit-Symbol Substitution. Linear mixed-effects models were used to compare the cognitive composite scores across the 4 groups over time, adjusting for baseline age, sex, education, and their interactions with time.Two hundred twenty-two cognitively normal participants were included in the analyses (mean follow-up, 11.0 years [range, 0-18.3 years] and mean baseline age, 56.9 years [range, 22.1-85.8 years]). Of these, 102 were stage 0, 46 were stage 1, 28 were stage 2, and 46 were SNAP. Individuals in stage 2 (low A? and high tau [or p-tau]) had lower baseline cognitive scores and a greater decline in the cognitive composite score relative to the other 3 groups (????-0.06 for all and P???.001 for the rate of decline for all). Individuals in stage 0, stage 1, and SNAP did not differ from one another in cognitive performance at baseline or over time (11.0 years) and showed practice-related improvement in performance. The APOE ?4 genotype was not associated with baseline cognitive composite score or the rate of change in the cognitive composite score.These results suggest that, to optimize observing a treatment effect, clinical trials enrolling cognitively normal individuals should selectively recruit participants with abnormal levels of both amyloid and tau (ie, stage 2) because this group would be expected to show the greatest cognitive decline over time if untreated.

Project description:ObjectiveTo examine the cross-sectional associations between regional tau, β-amyloid (Aβ), and cortical thickness and neuropsychological function across the preclinical and clinical spectrum of Alzheimer disease (AD).MethodsWe included 106 participants from the Swedish Biomarkers for Identifying Neurodegenerative Disorders Early and Reliably (BioFINDER) study, of whom 33 had preclinical AD (Aβ-positive cognitively normal individuals), 25 had prodromal AD (Aβ-positive mild cognitive impairment), and 48 had probable AD dementia. All underwent [18F]flortaucipir (tau) and structural MRI (cortical thickness), and 88 of 106 underwent [18F]flutemetamol (Aβ) PET. Linear regression models adjusted for age, sex, and education were performed to examine associations between 7 regions of interest and 7 neuropsychological tests for all 3 imaging modalities.ResultsIn preclinical AD, [18F]flortaucipir, but not [18F]flutemetamol or cortical thickness, was associated with decreased global cognition, memory, and processing speed (range standardized β = 0.35-0.52, p < 0.05 uncorrected for multiple comparisons). In the combined prodromal AD and AD dementia group, both increased [18F]flortaucipir uptake and reduced cortical thickness were associated with worse performance on a variety of neuropsychological tests (most regions of interest survived correction for multiple comparisons at p < 0.05), while increased [18F]flutemetamol uptake was specifically associated with lower scores on a delayed recall memory task (p < 0.05 uncorrected for multiple comparisons). The strongest effects for both [18F]flortaucipir and cortical thickness on cognition were found in the lateral and medial parietal cortex and lateral temporal cortex. The effect of [18F]flutemetamol on cognition was generally weaker and less region specific.ConclusionOur findings suggest that tau PET is more sensitive than Aβ PET and measures of cortical thickness for detecting early cognitive changes in preclinical AD. Furthermore, both [18F]flortaucipir PET and cortical thickness show strong cognitive correlates at the clinical stages of AD.

Project description:ImportanceThe amyloid/tau/neurodegeneration (A/T/N) framework uses cerebrospinal fluid (CSF) levels of total tau (tTau) as a marker of neurodegeneration and CSF levels of phosphorylated tau 181 (pTau181) as a marker of tau tangles. However, it is unclear whether CSF levels of tTau and pTau181 have similar or different trajectories over the course of Alzheimer disease.ObjectivesTo examine the rates of change in CSF levels of tTau and pTau181 across the Alzheimer disease course and how the rates of change are associated with brain atrophy as measured by magnetic resonance imaging.Design, setting, and participantsThis cohort study was set in tertiary research clinics. Each participant was a member of a pedigree with a known mutation for dominantly inherited Alzheimer disease. Participants were divided into 3 groups on the basis of the presence of a mutation and their Clinical Dementia Rating score. Data analysis was performed in June 2019.Main outcomes and measuresRates of change of CSF tTau and pTau181 levels and their association with the rate of change of brain volume.ResultsData from 465 participants (283 mutation carriers and 182 noncarriers) were analyzed. The mean (SD) age of the cohort was 37.8 (11.3) years, and 262 (56.3%) were women. The mean (SD) follow-up duration was 2.7 (1.5) years. Two or more longitudinal CSF and magnetic resonance imaging assessments were available for 160 and 247 participants, respectively. Sixty-five percent of mutation carriers (183) did not have symptoms at baseline (Clinical Dementia Rating score, 0). For mutation carriers, the annual rates of change for CSF tTau and pTau181 became significantly different from 0 approximately 10 years before the estimated year of onset (mean [SE] rates of change, 5.5 [2.8] for tTau [P = .05] and 0.7 [0.3] for pTau 181 [P = .04]) and 15 years before onset (mean [SE] rates of change, 5.4 [3.9] for tTau [P = .17] and 1.1 [0.5] for pTau181 [P = .03]), respectively. The rate of change of pTau181 was positive and increased at the early stages of the disease, showing a positive rate of change starting at 15 estimated years before onset until 5 estimated years before onset (mean [SE], 0.4 [0.3]), followed by a positive but decreasing rate of change at year 0 (mean [SE], 0.1 [0.3]) and then negative rates of change at 5 years (mean [SE], -0.3 [0.4]) and 10 years (mean [SE], -0.6 [0.6]) after symptom onset. In individuals without symptoms (Clinical Dementia Rating score, 0), the rates of change of CSF tTau and pTau181 were negatively associated with brain atrophy (high rates of change in CSF measures were associated with low rates of change in brain volume in asymptomatic stages). After symptom onset (Clinical Dementia Rating score, >0), an increased rate of brain atrophy was not associated with rates of change of levels of both CSF tTau and pTau181.Conclusions and relevanceThese findings suggest that CSF tTau and pTau181 may have different associations with brain atrophy across the disease time course. These results have implications for understanding the dynamics of disease pathobiology and interpreting neuronal injury biomarker concentrations in response to Alzheimer disease progression and disease-modifying therapies.

Project description:ImportanceCharacterization of early tau deposition in individuals with preclinical Alzheimer disease (AD) is critical for prevention trials that aim to select individuals at risk for AD and halt the progression of disease.ObjectiveTo evaluate the prevalence of cortical tau positron emission tomography (PET) heterogeneity in a large cohort of clinically unimpaired older adults with elevated β-amyloid (A+).Design, setting, and participantsThis cross-sectional study examined prerandomized tau PET, amyloid PET, structural magnetic resonance imaging, demographic, and cognitive data from the Anti-Amyloid Treatment in Asymptomatic AD (A4) Study from April 2014 to December 2017. Follow-up analyses used observational tau PET data from the Alzheimer's Disease Neuroimaging Initiative (ADNI), the Harvard Aging Brain Study (HABS), and the Wisconsin Registry for Alzheimer's Prevention and the Wisconsin Alzheimer's Disease Research Center (together hereinafter referred to as Wisconsin) to evaluate consistency. Participants were clinically unimpaired at the study visit closest to the tau PET scan and had available amyloid and tau PET data (A4 Study, n = 447; ADNI, n = 433; HABS, n = 190; and Wisconsin, n = 328). No participants who met eligibility criteria were excluded. Data were analyzed from May 11, 2021, to January 25, 2022.Main outcomes and measuresIndividuals with preclinical AD with heterogeneous cortical tau PET patterns (A+T cortical+) were identified by examining asymmetrical cortical tau signal and disproportionate cortical tau signal relative to medial temporal lobe (MTL) tau. Voxelwise tau patterns, amyloid, neurodegeneration, cognition, and demographic characteristics were examined.ResultsThe 447 A4 participants (A+ group, 392; and normal β-amyloid group, 55), with a mean (SD) age of 71.8 (4.8) years, included 239 women (54%). A total of 36 individuals in the A+ group (9% of the A+ group) exhibited heterogeneous cortical tau patterns and were further categorized into 3 subtypes: asymmetrical left, precuneus dominant, and asymmetrical right. A total of 116 individuals in the A+ group (30% of the A+ group) showed elevated MTL tau (A+T MTL+). Individuals in the A+T cortical+ group were younger than those in the A+T MTL+ group (t61.867 = -2.597; P = .03). Across the A+T cortical+ and A+T MTL+ groups, increased regional tau was associated with reduced hippocampal volume and MTL thickness but not with cortical thickness. Memory scores were comparable between the A+T cortical+ and A+T MTL+ groups, whereas executive functioning scores were lower for the A+T cortical+ group than for the A+T MTL+ group. The prevalence of the A+T cortical+ group and tau patterns within the A+T cortical+ group were consistent in ADNI, HABS, and Wisconsin.Conclusions and relevanceThis study suggests that early tau deposition may follow multiple trajectories during preclinical AD and may involve several cortical regions. Staging procedures, especially those based on neuropathology, that assume a uniform trajectory across individuals are insufficient for disease monitoring with tau imaging.

Dataset Information

Association of Amyloid and Tau With Cognition in Preclinical Alzheimer Disease: A Longitudinal Study.

Publications

Association of Amyloid and Tau With Cognition in Preclinical Alzheimer Disease: A Longitudinal Study.

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