Objective: To compare the cognitive effects of donepezil and placebo treatment, as assessed by the Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-cog), in vascular dementia (VaD) versus Alzheimer's disease (AD) patients.
Design: Combined analysis of two 24-week, double-blind studies in patients with probable or possible VaD, and results from a similar study in patients with probable AD.
Materials and Methods: Patients were randomized to receive placebo or donepezil (5 or 10 mg/day). Data are presented separately for those patients that showed any improvement from baseline and those who showed any decline from baseline on the ADAS-cog for the intent-to-treat population at Week 24 (LOCF analysis).
Results: 1219 VaD patients (placebo, n=392; donepezil 5 mg/day, n=406; 10 mg/day, n=421) and 473 AD patients (placebo, n=162; donepezil 5 mg/day, n=154; 10 mg/day, n=157) were enrolled. More donepezil- than placebo-treated patients showed improvement, both in VaD (placebo, 37%; donepezil 5 mg/day, 53%; 10 mg/day, 54%), and in AD (placebo, 27%; donepezil 5 mg/day, 38%; 10 mg/day, 54%). Fewer donepezil- than placebo-treated patients declined, both in VaD (placebo, 19%; donepezil 5 mg/day, 12%; 10 mg/day, 12%), and in AD (placebo, 42%; donepezil 5 mg/day, 20%; 10 mg/day, 19%).
Conclusion: Although there were a variety of responses observed within all treatment groups, both in AD and in VaD, donepezil-treated patients were more likely than placebo-treated patients to show cognitive improvements, as measured on the ADAS-cog. The number of patients showing a response to donepezil (10 mg/day) was similar in VaD and AD patients, with >50% improving by ³4 points and >80% showing no decline. Placebo-treated VaD patients were less likely to show decline than placebo-treated AD patients. Therefore, differing treatment effect sizes in VaD versus AD may be explained by differences in placebo response, since in VaD patients significant treatment effects have to be driven by improvement.
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