The long-term efficacy of donepezil for the treatment of cognitive impairment in mild to moderate AD (MMSE score of 10–26) has also been established in a double-blind, placebo-controlled study. Specifically, the MMSE scores of patients with mild to moderate AD receiving donepezil (10 mg/day) were maintained at close to base-line levels over the course of one year, while patients receiving placebo showed significant cognitive deterioration. Data from long-term, open-label studies of up to 4.9 years in patients with mild to moderate AD have also demonstrated that treatment with donepezil (10 mg/day) slows the expected rate of cognitive decline, as measured by ADAS-cog scores.

The effect of donepezil on cognitive symptoms in persons with moderate to severe AD was demonstrated in a double-blind, placebo- controlled trial. In this study, MMSE scores were improved and significantly different from placebo following six months of donepezil (10 mg/day) treatment.