Objective: The purpose of the present study was to clarify as to which cognitive functions are improved by donepezil hydrochloride (DPZ) in patients with dementia of Alzheimer's type (DAT).
Design: We assessed the initial effect of DPZ on various aspects of cognitive function in patients with DAT by using the Japanese version of the Wechsler Adult Intelligence Scale-Revised (WAIS-R).
Materials and Methods: A hundred consecutive outpatients with mild-to-moderate DAT (meeting the NINCDS-ADRDA criteria for the diagnosis of probable Alzheimer's disease) were divided into two groups. Thirty nine patients received 3 mg/day DPZ for two weeks, after which the dose was increased to 5 mg/day (D group). The control group consisted of 61 patients who had been followed up before DPZ was released for use (C group). Both groups underwent WAIS-R testing, before and after 10 months of treatment with DPZ for group D, and at the time of diagnosis of DAT and 10 months later for group C.
Results: The D and C groups did not differ significantly in terms of gender ratio (D: 13 males; 26 females, C: 21 males; 40 females), years of education(D: 10.7±3.5, C: 10.2±3.3), age at onset of DAT (D: 70.5±8.8, C: 68.7±8.6), age at administration of DPZ or at diagnosis of DAT(D: 74.2±7.7, C: 72.8±8), severity of dementia (D: mild 24; moderate 15, C: mild 37; moderate 24), MMSE score (D: 17.3±4.7, C: 19±5.2), presence of BPSD (D: 13, C: 30), concomitant use of psychotropic medication (D: 8, C: 22), and initiation of rehabilitation (D: 16, C: 26). No significant difference was found between the D and C groups in verbal (V), performance (P) and full-scale (F) Intelligent Quotient (IQ), and in six verbal subtest scores of VIQ and five performance subtest scores of PIQ on WAIS-R, at administration of DPZ or diagnosis of DAT. However, in comparison of differences between each score on WAIS-R at diagnosis of DAT or administration of DPZ and 10 months later, the decline observed in group D was significantly less than that observed in group C.
Conclusion: DPZ was not effective in improving cognitive function in patients with DAT. However, DPZ inhibited the decrease of FIQ and of VIQ, PIQ, vocabulary, similarities, picture arrangement and object assembly subtest scores on WAIS-R. These indices are related to concept formation and abstract thinking, which form part of executive function. DPZ effectively prevented decline of cognitive function, particularly executive function, in patients with DAT.
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