Aim: This study examined the significance of age-related subtest scores from the Japanese version of the Wechsler Adult Intelligence Scale-III in patients in the early stages of Alzheimer's disease (AD).
Methods: The subjects of this study included 58 elderly Japanese persons classified into two groups: AD group (n = 29) and control group (n = 29). These groups did not differ in age, years of education, gender ratio, Hasegawa's Dementia Scale-Revised score, or Full-Scale IQ score. No subject scored below the cut-off point on Hasegawa's Dementia Scale-Revised, a frequently used dementia screen test in Japan.
Results: At the index score level, General Ability Index scores were the only scores that differed significantly between the groups, with the AD group scoring significantly lower than the control group (P < 0.05, Hedges' g = 0.54). At the subtest level, information scores were the only scores that differed significantly between the groups, with the AD group significantly lower than the control group (P < 0.01, Hedges' g = 0.74).
Conclusion: The General Ability Index is a composite score that deducts components of working memory and processing speed, which are sensitive to decline with normal ageing, from the Full-Scale IQ. It also served as a subtest measuring crystallized intelligence, especially of acquired knowledge of general and factual information. Therefore, the results of this study seem to suggest that Wechsler Adult Intelligence Scale-III profile of very early AD may be characterized by weak performance on subtests normally resistant to decline with ageing.
Keywords: WAIS-III profile; crystallized intelligence; early Alzheimer's disease.
© 2014 The Authors. Psychogeriatrics © 2014 Japanese Psychogeriatric Society.