Wechsler adult intelligence scale-4th edition digit span performance in subjective cognitive complaints, amnestic mild cognitive impairment, and probable dementia of the Alzheimer type

Objective: The Digit Span (DS) subtest from the Wechsler Adult Intelligence Scale-4^th Edition (WAIS-IV) was updated to better measure working memory which is potentially clinically relevant as prior unreplicated studies showed that sequencing tasks differentiated normal from neurologic groups. This study examines performance on DS for individuals from a memory disorder clinic diagnosed with amnestic mild cognitive impairment (aMCI), probable dementia of the Alzheimer type (DAT), or those with subjective cognitive complaints (SCC). Method: Seven hundred and six individuals were drawn from 1256 consecutive referrals who underwent a standard neuropsychological evaluation and obtained a consensus diagnosis from a neuropsychologist and a neurologist of DAT, aMCI, or having SCC. This resulted in a sample of 290 individuals with DAT, 255 with aMCI, and 161 with SCC. Results: Those with DAT performed significantly worse for DS Forward, Backward, and Total Score versus those with aMCI and SCC, whose performances were similar. Digit Span Sequencing was significantly different in each group (DAT < aMCI < SCC), with a high rate of the DAT group showing cross-task perseveration. Conclusions: The DS sequencing results differed between the three clinical groups, which is consistent with the hypothesis that working memory declines would be evident on this measure. Discontinuation of DSS due to cross-task perseveration was frequently seen in, although not unique to, the DAT group. Both poorer DSS performance and the presence of perseveration can offer useful clinical information on the context of a thorough evaluation of the aMCI/DAT spectrum.