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Title: Association of β-Amyloid and Apolipoprotein E ε4 With Memory Decline in Preclinical Alzheimer Disease.
Austin Authors: Lim, Yen Ying;Kalinowski, Pawel;Pietrzak, Robert H;Laws, Simon M;Burnham, Samantha C;Ames, David;Villemagne, Victor L ;Fowler, Christopher J;Rainey-Smith, Stephanie R;Martins, Ralph N;Rowe, Christopher C ;Masters, Colin L ;Maruff, Paul T
Affiliation: The Florey Institute of Neuroscience and Mental Health, University of Melbourne, Parkville, Victoria, Australia
CogState, Ltd, Melbourne, Victoria, Australia
Department of Psychiatry, Yale University School of Medicine, New Haven, Connecticut
Centre of Excellence for Alzheimer's Disease Research and Care, Edith Cowan University, Joondalup, Western Australia, Australia
Sir James McCusker Alzheimer's Disease Research Unit, Hollywood Private Hospital, Perth, Western Australia, Australia
Cooperative Research Centre for Mental Health, Carlton, Victoria, Australia
Commonwealth Scientific and Industrial Research Organisation Preventative Health National Research Flagship, Australian e-Health Research Centre, Brisbane, Queensland, Australia
Academic Unit for Psychiatry of Old Age, St Vincent's Health, University of Melbourne, Kew, Victoria, Australia
National Ageing Research Institute, Parkville, Victoria, Australia
Department of Nuclear Medicine and Centre for PET, Austin Health, Heidelberg, Victoria, Australia
Department of Medicine, Austin Health, The University of Melbourne, Heidelberg, Victoria, Australia
Issue Date: 22-Jan-2018
Date: 2018-01-22
Publication information: JAMA neurology 2018; 75(4): 488-494
Abstract: Older age, high levels of β-amyloid (Aβ), and the presence of the apolipoprotein E (APOE) ε4 allele are risk factors for Alzheimer disease (AD). However, the extent to which increasing age, Aβ, and ε4 are associated with memory decline remains unclear, and the age at which memory decline begins for Aβ-positive ε4 carriers and noncarriers has not been determined. To determine the association of age, Aβ level, and APOE ε4 with memory decline in a large group of cognitively healthy older adults. 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 Aβ 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. β-Amyloid imaging using positron emission tomography, genotyping for APOE ɛ4, and longitudinal neuropsychological assessments of episodic memory during the 72-month follow-up. Episodic memory composite score. 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 Aβ-ɛ4 group (24 of 51 Aβ-positive ε4 noncarriers [47.1%] ; 35 of 64 Aβ-negative ε4 carriers [54.7%]; 40 of 72 Aβ-positive ε4 carriers [55.6%]; and 145 of 260 Aβ-negative ε4 noncarriers [55.8%]). Adults with Aβ findings (mean [SD] age, 74.4 [6.8] years) were approximately 4 years older than those negative for Aβ (mean [SD] age, 69.8 [6.1] years). Memory decline diverged significantly from Aβ-negative ɛ4 noncarriers at an earlier age in Aβ-positive ɛ4 carriers (64.5 years) than in Aβ-positive ɛ4 noncarriers (76.5 years), such that by 85 years of age, Aβ-positive ε4 carriers performed approximately 1.5 SD units worse on the episodic memory composite than Aβ-negative ε4 noncarriers and approximately 0.8 SD units worse than Aβ-positive ε4 noncarriers. Memory performance of Aβ-negative ɛ4 carriers did not differ from that of the Aβ-negative ɛ4 noncarriers (estimate [SE], 0.001 [0.001]; t = 0.526; P = .77). Prior work has shown that Aβ and ε4 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 Aβ and ε4 at each age.
DOI: 10.1001/jamaneurol.2017.4325
ORCID: 0000-0003-3910-2453
Journal: JAMA neurology
PubMed URL: 29356823
Type: Journal Article
Appears in Collections:Journal articles

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