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
Hamid R. Sohrabi, Edith Cowan UniversityFollow
Stephanie Rainey-Smith, Edith Cowan UniversityFollow
Belinda M Brown
Samantha L Gardener
Aleksandra Gozt, Edith Cowan UniversityFollow
Simon Laws, Edith Cowan UniversityFollow
Kevin Taddei, Edith Cowan UniversityFollow
Joanne S Robertson
Kathryn A Ellis
Colin L Masters
Christopher C Rowe
Ralph Martins, Edith Cowan UniversityFollow
American Psychological Association Inc.
School of Medical and Health Sciences
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. (PsycINFO Database Record (c) 2018 APA, all rights reserved).