Donepezil

People with mild cognitive impairment taking the medication donepezil were at reduced risk of progressing to Alzheimer's disease during the first 18 months of a three-year study when compared with their counterparts who were taking a placebo, according to a July 18, 2004, news release from the National Institutes of Health. The reduced risk of progressing from mild cognitive impairment to a diagnosis of Alzheimer's disease among participants on donepezil no longer existed after 18 months, and by the end of the study, the probability of progressing to Alzheimer's disease was the same in the two groups.

The study compared donepezil, vitamin E, and placebo in participants with mild cognitive impairment to see whether the medications would delay or prevent progression to Alzheimer's disease. During the course of the study, among people who did progress to Alzheimer's disease, the participants taking donepezil averaged 661 days until a diagnosis of Alzheimer's disease; a second group taking vitamin E averaged 540 days from mild cognitive impairment to Alzheimer's disease; and those taking placebo averaged 484 days to Alzheimer's disease. The investigators reported a statistically significant effect when donepezil was compared to placebo but said there was no apparent benefit from vitamin E.

The National Institute on Aging and the scientists conducting the study emphasized that further analyses are needed to assess the practical, clinical implications of the new data. The study is complex, and the effects appear to be time limited.

People with mild cognitive impairment have notable memory Loss and are at higher risk for developing Alzheimer's disease than those of similar age and health in the general population. Donepezil was used in the study because of its current approval as a medication for treating patients already diagnosed with Alzheimer's disease. The antioxidant vitamin E has been linked in animal research to a reduction in cognitive decline and in some population studies to reduced risk of Alzheimer's disease.

In addition to being tested for Alzheimer's disease, study participants were assessed in specific areas of cognitive function, including orientation, Language, and attention, and in everyday function (ie, activities of daily living). These secondary analyses suggest that decline among the group taking donepezil occurred at a slower rate on tests of global cognition, memory, and language than among the other participants during the first half of the study but progressed at the same rate thereafter.

The Memory Impairment Study was conducted nationwide at 69 sites. It involved 769 participants with mild cognitive impairment, who were followed for three years and tested for Alzheimer's disease at six-month intervals during their 36 months in the study. The average age of the participants was 73 years.

Donepezil May Have Short-Term Benefit for Mild Cognitive Impairment; More Analyses Needed to Assess Clinical Implications of New Data (news release, Bethesda, Md: National Institutes of Health, July 18, 2004) http://www.nih.gov/news/pr/jul2004/nia-18.htm (accessed 3 Aug 2004).

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