Episodic Memory and Learning Dysfunction Over an 18-Month Period in Preclinical and Prodromal Alzheimer’s Disease

Article type: Research Article

Authors: Baker, Jenalle E.^{a; b; *} | Lim, Yen Ying^{a; #} | Jaeger, Judith^{c; d} | Ames, David^{e; f} | Lautenschlager, Nicola T.^f | Robertson, Joanne^a | Pietrzak, Robert H.^{g; h} | Snyder, Peter J.ⁱ | Villemagne, Victor L.^{a; j; k} | Rowe, Christopher C.^{j; k} | Masters, Colin L.^a | Maruff, Paul^{a; l; #}

Affiliations: [a] The Florey Institute of Neuroscience and Mental Health, Parkville, Victoria, Australia | [b] Cooperative Research Centre for Mental Health, Carlton, Victoria, Australia | [c] CognitionMetrics, LLC., Wilmington, DE, USA | [d] Albert Einstein College of Medicine, Bronx, NY, USA | [e] National Ageing Research Institute, Parkville, VIC, Australia | [f] Department of Psychiatry, Academic Unit for Psychiatry of Old Age, The University of Melbourne, St. George’s Hospital, Kew, VIC, Australia | [g] U.S. Department of Veterans Affairs National Center for Posttraumatic Stress Disorder, Clinical Neurosciences Division, VA Connecticut Healthcare System, West Haven, CT, USA | [h] Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA | [i] Ryan Institute for Neuroscience, University of Rhode Island, Kingston, RI, USA | [j] Department of Nuclear Medicine and Centre for PET, Austin Health, Heidelberg, VIC, Australia | [k] Department of Medicine, Austin Health, The University of Melbourne, Heidelberg, VIC, Australia | [l] Cogstate Ltd., Melbourne, VIC, Australia

Correspondence: [*] Correspondence to: Jenalle Baker, 30 Royal Parade, Parkville, VIC 3052, Australia. Tel.: +61 614 23 271 223; E-mail: jenalle.baker@florey.edu.au.

Note: [#] Co-senior authors.

Abstract: Recent meta-analyses suggest that episodic memory impairment associated with preclinical Alzheimer’s disease (AD) equates to 0.15–0.24 standard deviations below that of cognitively healthy older adults. The current study aimed to characterize impairments in verbal acquisition and recall detectable at a single assessment, and investigate how verbal learning and episodic memory deteriorates in preclinical AD. A verbal list-learning task, the International Shopping List Test (ISLT), was administered multiple times over an 18-month period, to three groups of participants: amyloid-beta negative healthy older adults (Aβ– CN; n = 50); Aβ+ positive healthy older adults (preclinical AD; n = 25); and Aβ+ positive individuals diagnosed with mild cognitive impairment (prodromal AD; n = 22). At baseline, there was no significant difference between the preclinical AD and control groups rate of acquisition, or total and delayed recall, however all indices were impaired in prodromal AD. Performance on ISLT total score improved in the control group over the 18-month period, but showed a moderate magnitude decline in the preclinical AD group (Cohen’s d = – 0.63, [– 1.12, – 0.14]) and the prodromal AD group (Cohen’s d = – 0.36, [– 0.94, 0.22]). No significant impairment in acquisition associated with preclinical AD was seen at baseline. Individuals with preclinical AD showed a significantly different performance on the ISLT total score over an 18-month period, compared to those without abnormal Aβ. Individuals with prodromal AD showed substantial impairment on the ISLT at baseline and declined to a greater extent over time.

Keywords: Alzheimer’s disease, amyloid-β protein, cognitive decline, learning curve, memory and learning tests, mild cognitive impairment, neuropsychology, transfer of learning

DOI: 10.3233/JAD-180344

Journal: Journal of Alzheimer's Disease, vol. 65, no. 3, pp. 977-988, 2018