Trajectories of irregular word reading ability as a proxy for premorbid intelligence in Alzheimer's disease, mild cognitive impairment, and healthy aging

a longitudinal study

Michael Weinborn*, Romola S. Bucks, Hamid R. Sohrabi, Stephanie R. Rainey-Smith, Belinda M. Brown, Samantha L. Gardener, Aleksandra Gozt, Daniel Christensen, Greg Savage, Simon M. Laws, Kevin Taddei, Paul Maruff, Joanne S. Robertson, Kathryn A. Ellis, David Ames, Colin L. Masters, Christopher C. Rowe, Ralph N. Martins

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

The ability to read irregularly spelled words is commonly used to estimate premorbid intelligence, as this ability has been thought to be resistant to early effects of neurodegenerative disorders. However, studies evaluating decline of this skill in Alzheimer's disease (AD) have produced conflicting results. Irregular word reading was assessed three times over 36 months in a large (N = 995) sample, including healthy control, AD, and Mild Cognitive Impairment (MCI) groups. At baseline, MCI and AD groups read correctly an average of 3.01 and 7.39 fewer words, respectively, than healthy controls. The MCI group's performance remained stable during the study, but the AD group declined. Importantly, the observed decline was likely an underestimate, as significant numbers of the AD participants (42.6%) could not complete the task at follow-up. Use of alternate (e.g., demographics-based) methods is advised to augment or replace word pronunciation in estimating premorbid intelligence in individuals with even mild AD.

Original languageEnglish
Pages (from-to)1308-1316
Number of pages9
JournalPsychological Assessment
Volume30
Issue number10
DOIs
Publication statusPublished - 1 Oct 2018

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Keywords

  • Alzheimer's disease
  • Cognitive reserve
  • Irregular word reading
  • Mild cognitive impairment
  • Premorbid intelligence
  • WTAR

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