Dataset Information

Association of Elevated Amyloid Levels With Cognition and Biomarkers in Cognitively Normal People From the Community.

ABSTRACT: The role of amyloid in the progression of Alzheimer disease (AD) pathophysiology is of central interest to the design of randomized clinical trials. The presence of amyloid has become a prerequisite for enrollment in several secondary prevention trials for AD, yet the precise effect of elevated amyloid levels on subsequent clinical and biomarker events is less certain.To explore the effect of elevated amyloid levels on subsequent changes in cognition and biomarkers.A total of 564 cognitively normal individuals (median age, 78 years) from the Mayo Clinic Study of Aging, a population-based longitudinal study in Olmsted County, Minnesota, with serial cognitive data were selected for this study. The data used in this study were collected from January 12, 2006, to January 9, 2014. Individuals included in this study had undergone magnetic resonance imaging, fluorodeoxyglucose positron emission tomography (FDG-PET), and Pittsburgh Compound B (PiB) PET at baseline were not cognitively impaired at baseline and had at least 1 clinical follow-up. A subset of 286 individuals also underwent serial imaging. Elevated amyloid level was defined as a standardized uptake value ratio of greater than 1.5 on PiB PET. Associations with baseline amyloid status and baseline and longitudinal change in clinical and imaging measures were evaluated after adjusting for age and hippocampal volume. APOE4 effects were also evaluated.Cognitive measures of memory, language, attention/executive function, visuospatial skills, PiB levels, hippocampal and ventricular volumes, and FDG-PET measures.At baseline, 179 (31.7%) individuals with elevated amyloid levels had poorer cognition in all domains measured, reduced hippocampal volume, and greater FDG-PET hypometabolism. Elevated amyloid levels at baseline were associated with a greater rate of cognitive decline in all domains (0.04 to 0.09 z score units per year) except language and a greater rate of amyloid accumulation (1.6% per year), hippocampal atrophy (30 mm3 per year), and ventricular enlargement (565 mm3 per year). Elevated amyloid levels were also associated with an increased risk of mild cognitive impairment (hazard ratio, 2.9; 95% CI, 1.7-5.0, and hazard ratio, 1.6; 95% CI, 0.9-2.8, for PiB+ APOE4 carriers and PiB+ noncarriers, respectively, compared with PiB- noncarriers). These associations were largely independent of APOE4.In persons selected from a population-based study, elevated amyloid levels at baseline were associated with worse cognition and imaging biomarkers at baseline and with greater clinical decline and neurodegeneration. These results have implications for the design of randomized clinical trials for AD.

SUBMITTER: Petersen RC

PROVIDER: S-EPMC4710552 | biostudies-literature | 2016 Jan

REPOSITORIES: biostudies-literature

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Association of Elevated Amyloid Levels With Cognition and Biomarkers in Cognitively Normal People From the Community.

Petersen Ronald C RC Wiste Heather J HJ Weigand Stephen D SD Rocca Walter A WA Roberts Rosebud O RO Mielke Michelle M MM Lowe Val J VJ Knopman David S DS Pankratz Vernon S VS Machulda Mary M MM Geda Yonas E YE Jack Clifford R CR

JAMA neurology 20160101 1

<h4>Importance</h4>The role of amyloid in the progression of Alzheimer disease (AD) pathophysiology is of central interest to the design of randomized clinical trials. The presence of amyloid has become a prerequisite for enrollment in several secondary prevention trials for AD, yet the precise effect of elevated amyloid levels on subsequent clinical and biomarker events is less certain.<h4>Objective</h4>To explore the effect of elevated amyloid levels on subsequent changes in cognition and biom ...[more]

PMID: 26595683

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Project description:Among cognitively normal individuals, elevated brain amyloid (defined by cerebrospinal fluid assays or positron emission tomography regional summaries) can be related to risk for later Alzheimer-related cognitive decline.To characterize and quantify the risk for Alzheimer-related cognitive decline among cognitively normal individuals with elevated brain amyloid.Exploratory analyses were conducted with longitudinal cognitive and biomarker data from 445 cognitively normal individuals in the United States and Canada. Participants were observed from August 23, 2005, to June 7, 2016, for a median of 3.1 years (interquartile range, 2.0-4.2 years; maximum follow-up, 10.3 years) as part of the Alzheimer's Disease Neuroimaging Initiative (ADNI).Individuals were classified at baseline as having normal (n?=?243) or elevated (n?=?202) brain amyloid using positron emission tomography amyloid imaging or a cerebrospinal fluid assay of amyloid ?.Outcomes included scores on the Preclinical Alzheimer Cognitive Composite (PACC; a sum of 4 baseline standardized z scores, which decreases with worse performance), Mini-Mental State Examination (MMSE; 0 [worst] to 30 [best] points), Clinical Dementia Rating Sum of Boxes (CDR-Sum of Boxes; 0 [best] to 18 [worst] points), and Logical Memory Delayed Recall (0 [worst] to 25 [best] story units).Among the 445 participants (243 with normal amyloid, 202 with elevated amyloid), mean (SD) age was 74.0 (5.9) years, mean education was 16.4 (2.7) years, and 52% were women. The mean score for PACC at baseline was 0.00 (2.60); for MMSE, 29.0 (1.2); for CDR-Sum of Boxes, 0.04 (0.14); and for Logical Memory Delayed Recall, 13.1 (3.3). Compared with the group with normal amyloid, those with elevated amyloid had worse mean scores at 4 years on the PACC (mean difference, 1.51 points [95% CI, 0.94-2.10]; P?<?.001), MMSE (mean difference, 0.56 points [95% CI, 0.32-0.80]; P?<?.001), and CDR-Sum of Boxes (mean difference, 0.23 points [95% CI, 0.08-0.38]; P?=?.002). For Logical Memory Delayed Recall, between-group score was not statistically significant at 4 years (mean difference, 0.73 story units [95% CI, -0.02 to 1.48]; P?=?.056).Exploratory analyses of a cognitively normal cohort followed up for a median of 3.1 years suggest that elevation in baseline brain amyloid level, compared with normal brain amyloid level, was associated with higher likelihood of cognitive decline, although the findings are of uncertain clinical significance. Further research is needed to assess the clinical importance of these differences and measure longer-term associations.

Project description:Importance:The goal of Alzheimer disease (AD) prevention together with advances in understanding the pathophysiology of AD have led to clinical trials testing drugs in cognitively unimpaired persons who show evidence of AD biomarkers. Data are needed to inform the processes of describing AD biomarkers to cognitively normal adults and assessing their understanding of this knowledge. Objective:To determine the comprehension of an elevated amyloid positron emission tomographic (PET) biomarker result by cognitively unimpaired adults. Design, Setting, and Participants:The Study of Knowledge and Reactions to Amyloid Testing, a substudy of an AD prevention trial, involved 2 semistructured telephone interviews with 80 participants recruited from 9 study sites: 50 received elevated and 30 received not elevated amyloid PET scan results. Interviews were conducted 4 to 12 weeks after result disclosure and again 1 year later. Data presented here were collected from November 5, 2014, through December 10, 2015. The 50 participants included in this study were cognitively normal, aged 65 to 85 years, evenly distributed by gender, and had elevated amyloid PET results. Subsequent reports will examine persons with "not elevated" results and compare the influence of the different results. Main Outcomes and Measures:Participant comprehension of an elevated amyloid result was assessed by analyzing their responses to the following questions: "What was the result of your amyloid PET scan?" (followed by "Can you tell me in your own words what that means?" or "How would you explain it to a friend?"), "Was it the result you expected?" and "Did the result teach you anything or clarify anything for you?" Results:Of the 50 participants aged 65 to 85 years, 49 (98%) were white, 40 (80%) reported a family history of AD, and 30 (60%) had a postgraduate educational level. Most participants (31 [62%]) understood that elevated amyloid conferred an increased but uncertain risk of developing AD. Some desired understanding of the term elevated other than its being a categorical result enabling trial entry eligibility; they wanted information regarding how elevated their amyloid was, how close to the study threshold they were, or percentages, numbers, or a scale to help them make sense of the result. Conclusions and Relevance:Including an explanation of how and why a dimensional biomarker is converted to a categorical classification would enhance future AD biomarker clinical trials and educational materials.

Project description:Importance:Emotional and behavioral symptoms in cognitively normal older people may be direct manifestations of Alzheimer disease (AD) pathophysiology at the preclinical stage, prior to the onset of mild cognitive impairment. Loneliness is a perceived state of social and emotional isolation that has been associated with cognitive and functional decline and an increased risk of incident AD dementia. We hypothesized that loneliness might occur in association with elevated cortical amyloid burden, an in vivo research biomarker of AD. Objective:To determine whether cortical amyloid burden is associated with greater loneliness in cognitively normal older adults. Design, Setting, and Participants:Cross-sectional analyses using data from the Harvard Aging Brain Study of 79 cognitively normal, community-dwelling participants. A continuous, aggregate measure of cortical amyloid burden, determined by Pittsburgh Compound B-positron emission tomography (PiB-PET), was examined in association with loneliness in linear regression models adjusting for age, sex, apolipoprotein E ?4 (APOE?4), socioeconomic status, depression, anxiety, and social network (without and with the interaction of amyloid and APOE?4). We also quantified the association of high amyloid burden (amyloid-positive group) to loneliness (lonely group) using logistic regression, controlling for the same covariates, with the amyloid-positive group and the lonely group, each composing 32% of the sample (n?=?25). Main Outcomes and Measures:Loneliness, as determined by the 3-item UCLA Loneliness Scale (possible range, 3-12, with higher score indicating greater loneliness). Results:The 79 participants included 43 women and 36 men with a mean (SD) age of 76.4 (6.2) years. Mean (SD) cortical amyloid burden via PiB-PET was 1.230 (0.209), and the mean (SD) UCLA-3 loneliness score was 5.3 (1.8). Twenty-two (28%) had positive APOE?4 carrier status, and 25 (32%) were in the amyloid-positive group with cortical PiB distribution volume ratio greater than 1.2. Controlling for age, sex, APOE?4, socioeconomic status, depression, anxiety, and social network, we found that higher amyloid burden was significantly associated with greater loneliness: compared with individuals in the amyloid-negative group, those in the amyloid-positive group were 7.5-fold (95% CI, 1.7-fold to 34.0-fold) more likely to be classified as lonely than nonlonely (??=?3.3, partial r?=?0.4, P?=?.002). Furthermore, the association of high amyloid burden and loneliness was stronger in APOE?4 carriers than in noncarriers. Conclusions and Relevance:We report a novel association of loneliness with cortical amyloid burden in cognitively normal older adults, suggesting that loneliness is a neuropsychiatric symptom relevant to preclinical AD. This work will inform new research into the neural underpinnings and disease mechanisms involved in loneliness and may enhance early detection and intervention research in AD.

Dataset Information

Association of Elevated Amyloid Levels With Cognition and Biomarkers in Cognitively Normal People From the Community.

Publications

Association of Elevated Amyloid Levels With Cognition and Biomarkers in Cognitively Normal People From the Community.

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