Cognitive Decline in Adults with Amnestic Mild Cognitive Impairment and High Amyloid-β: Prodromal Alzheimer's Disease?

Article type: Research Article

Authors: Lim, Yen Ying^{a; b; *} | Ellis, Kathryn A.^{a; c; d} | Harrington, Karra^a | Pietrzak, Robert H.^e | Gale, Joanne^f | Ames, David^{c; d} | Bush, Ashley I.^a | Darby, David^{a; g} | Martins, Ralph N.^h | Masters, Colin L.^a | Rowe, Christopher C.^{i; j} | Savage, Greg^k | Szoeke, Cassandra^{a; d} | Villemagne, Victor L.^{a; i; j} | Maruff, Paul^{a; f} | For the AIBL Research Group

Affiliations: [a] Mental Health Research Institute, The University of Melbourne, Parkville, VIC, Australia | [b] Department of Psychiatry, The University of Melbourne, Parkville, VIC, Australia | [c] Academic Unit for Psychiatry of Old Age, Department of Psychiatry, The University of Melbourne, St George's Hospital, Kew, VIC, Australia | [d] National Ageing Research Institute, Parkville, VIC, Australia | [e] Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA | [f] CogState Ltd., Melbourne, VIC, Australia | [g] Florey Neuroscience Institutes, The University of Melbourne, Carlton South, VIC, Australia | [h] Centre of Excellence for Alzheimer's Disease Research and Care, School of Exercise, Biomedical and Health Sciences, Edith Cowan University, Perth, WA, Australia | [i] Department of Nuclear Medicine and Centre for PET, Austin Health, Heidelberg, VIC, Australia | [j] Department of Medicine, Austin Health, The University of Melbourne, Heidelberg, VIC, Australia | [k] Department of Psychology and ARC Centre of Excellence in Cognition and its Disorders, Macquarie University, Sydney, Australia

Correspondence: [*] Correspondence to: Yen Ying Lim, Mental Health Research Institute, 155 Oak Street, Parkville, VIC 3052, Australia. Tel.: +61 3 9389 2932; Fax: +61 3 9388 1698; E-mail: y.lim@mhri.edu.au.

Abstract: We aimed to characterize the nature and magnitude of cognitive decline in a group of adults with amnestic mild cognitive impairment (aMCI) with high and low levels of amyloid-β (Aβ) in relation to healthy older adults with low Aβ levels. Healthy older adults and adults with aMCI enrolled in the Australian Imaging, Biomarker, and Lifestyle study, completed the CogState brief battery at baseline and 18 months, and underwent positron emission tomography neuroimaging for Aβ at baseline. In this study, we included adults with MCI who had been classified as having high and low levels of Aβ and healthy older adults who had been classified as having low levels of Aβ. Linear model analyses adjusted for baseline cognitive function indicated that relative to healthy older adults with low Aβ, adults with aMCI and high Aβ showed greater decline in working memory and in verbal and visual episodic memory at 18 months. Adults with aMCI and low Aβ also showed greater decline in working memory; however they did not evidence any decline in episodic memory at 18 months. The results of our study suggests that relative to healthy older adults and adults with aMCI with low Aβ, adults with aMCI and high levels of Aβ showed faster rates of decline on measures of episodic memory over 18 months, and this was approximately twice that observed previously for healthy older adults with high Aβ levels.

Keywords: Alzheimer's disease, amyloid-β, cognitive change, cognitive neuropsychology, mild cognitive impairment

DOI: 10.3233/JAD-121771

Journal: Journal of Alzheimer's Disease, vol. 33, no. 4, pp. 1167-1176, 2013