Aricept, a drug licensed for treating Alzheimer’s disease, may slow the progression of mild cognitive impairment to dementia, according to researchers at the Mayo Clinic College of Medicine in Rochester, Minnesota, and in other centers.

Lead investigator Dr. Ronald C. Petersen told Reuters Health that although the effects of the Aricept (known technically as donepezil) were modest in people with signs of mental decline, “this is the first study that has been able to demonstrate any kind of effect of pushing back the window of diagnosis of Alzheimer’s disease.”

Petersen and colleagues studied 769 subjects aged 55 to 90 years with mild cognitive impairment, mostly related to memory. The subjects were randomly assigned to daily treatment with high doses of vitamin E, donepezil, or placebo for 3 years.

Results of the study, to be published in the New England Journal of Medicine, were released early to coincide with this week’s presentation of the results at the American Academy of Neurology meeting in Miami.

After 12 months, 16 subjects in the donepezil group had progressed to Alzheimer’s disease versus 38 in the placebo group - a significant difference. By the third year, the difference had narrowed, with 63 people in the donepezil group and 73 in the placebo group having developed Alzheimer’s.

Contrary to results of earlier, observational studies, the mental decline of study participants in the vitamin E group did not differ significantly from that in the placebo group.

In a related editorial, Dr. Deborah Blacker, from Harvard Medical School in Boston, suggests that these results are “hopeful,” given that a variety of agents for warding off Alzheimer’s disease are now in clinical trials.

“There is every reason to expect that at least some of these agents will prove effective,” she added, “and can be deployed early in the hope of stopping the disease process while function remains intact.”