(The Associated Press) -- People with a common memory disorder that often leads to Alzheimer's disease may be able to briefly delay that fate by taking a drug normally prescribed for Alzheimer's, a new study indicates.

But ultimately the drug Aricept doesn't cut the risk of getting the feared illness, despite an average delay of six months.

The lead author of the study, Dr. Ronald Petersen of the Mayo Clinic, said it was too early to make any recommendations for doctors and patients. He called the new results "a foot in the door" to finding more effective treatments.

The same study found no effect from vitamin E, long viewed as a possible weapon against Alzheimer's.

The experiment is the first to show that Alzheimer's can be delayed in people with the memory disorder, mild cognitive impairment, Petersen said. So researchers might be able to find other treatments that will produce more than the "modest" effect of Aricept, he said.

MCI may be at least as common as Alzheimer's, which afflicts some 4 million Americans. Petersen said it might appear in some 18 percent to 20 percent of people older than 65 who do not have Alzheimer's or other dementia. Most of these people go on to develop Alzheimer's, with about 10 percent to 15 percent receiving an Alzheimer's diagnosis each year, Petersen said.

People with MCI are more forgetful than normal for their age. They repeatedly forget important things like luncheon engagements and golfing dates, often enough that friends and family notice the problem. But they don't show other symptoms of Alzheimer's like impaired judgment or reasoning.

Petersen spoke in a telephone interview before presenting the study results Sunday in Philadelphia at the Ninth International Conference on Alzheimer's Disease and Related Disorders.

The study was financed by the federal government and the two companies that co-market Aricept in the United States, Pfizer Inc. and Eisai Inc. DSM Nutritional Products donated vitamin E.

The research included 769 MCI patients who took Aricept, vitamin E or a placebo pill daily. Those taking Aricept had a lower risk of developing Alzheimer's than patients on placebo did for the first 18 months of the study, but that difference evaporated in the following 18 months.

The patients on Aricept who ultimately developed Alzheimer's disease took an average of 22 months to do so, about six months longer than patients on a placebo.

Bill Thies, vice president for medical and scientific affairs of the Alzheimer's Association, said vitamin E "is used by almost anyone who's worried about Alzheimer's disease," whether because of a family history or a sense of slipping memory, and users will probably continue to take it despite the study's finding.

As for the evidence that Aricept can delay the transition from MCI to Alzheimer's, "I suspect there will be a lot of people interested in that" among doctors, patients and families, Thies said.

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