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Cognitive super-aging versus typical aging in community-dwelling older adults: Longitudinal trajectories in global cortical thickness over six years

Sohrabi, H.R.ORCID: 0000-0001-8017-8682, Gardener, S.L., Weinborn, M., Shen, K., Rainey-Smith, S.R., Brown, B.M.ORCID: 0000-0001-7927-2540, Taddei, K., Doecke, J.D., Salvado, O., Villemagne, V.L.L., Maruff, P., Savage, G., Ames, D., Masters, C.L., Rowe, C.C. and Martins, R.N. (2017) Cognitive super-aging versus typical aging in community-dwelling older adults: Longitudinal trajectories in global cortical thickness over six years. Alzheimer's & Dementia, 13 (7 Supp.). P1463.

Link to Published Version: https://doi.org/10.1016/j.jalz.2017.07.531
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Abstract

Background
It is common for older adults to experience decline in some cognitive functions with increasing age. Importantly, a subset, usually referred to as super-agers (SA; Rogalski, et al., 2013, J Cog Neurosc, 25: 29-36) live to an old age whilst continuing to maintain cognitive function at levels similar to demographically-matched peers at least 20-30 years their junior. The current study reports trajectories of change in cortical thickness on a well-defined group of SAs vs. typical agers (TA) followed longitudinally over six years in the Australian Imaging, Biomarkers & Lifestyle Study (AIBL) (Ellis et al., 2009, Int Psychogeriat, 2: 672-87).

Methods
Super-Agers were defined as individuals aged 60+ who scored in the normative range for individuals aged 30 – 44 on the CVLT-II, a test of verbal episodic memory, at baseline and two consecutive time-points 18 months apart. SAs additionally must have performed in the unimpaired range in all other cognitive domains, as compared to same-aged peers. Typical agers must have scored within the normal range on all cognitive measures compared with same-aged peers. This report describes data from 21 SAs and 24 TAs. The TAs were chosen from a larger group matched on age, education and gender to the SA group. All participants completed brain magnetic resonance imaging every 18 months for six years. We conducted multiple linear mixed models analyses to assess the association between preservation of cortical thickness in SAs and TAs.

Results
From 34 regions of interest identified as potentially differentiating SAs from TAs from previous neuroimaging studies, our results were consistent in finding greater cortical thinning amongst TAs in 20 of these regions (p-values ranging between ≤ .000 and .047), with an additional five regions at trend level (p-values ranging between ≥ .05 and .073). Using false discovery rates, we found significantly preserved thickness in three regions not previously reported including left superior parietal gyrus, left precuneus, and left paracentral lobule.

Conclusions
SAs and TAs displayed similar cortical thickness at baseline (p >.40), but showed different trajectories over time. The findings will be discussed in the context of current models of cognitive and brain reserve.

Item Type: Journal Article
Murdoch Affiliation: School of Psychology and Exercise Science
Publisher: Elsevier Inc.
Copyright: © 2017 Elsevier B.V.
URI: http://researchrepository.murdoch.edu.au/id/eprint/55935
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