Mild Cognitive Impairment. During the past several years, scientists have focused on a type of memory change called mild cognitive impairment (MCI) which is different from both Alzheimer's disease and normal age-related memory change. People with MCI have ongoing memory problems, but they do not have other losses such as confusion, attention problems, and difficulty with language. The NIA-funded Memory Impairment Study compared donepezil (Aricept), vitamin E, or placebo in participants with MCI to see whether the drugs might delay or prevent progression to Alzheimer's disease. The study found that the group with MCI taking the drug donepezil were at reduced risk of progressing to Alzheimer's disease for the first 18 months of a 3-year study when compared with their counterparts on placebo.
The reduced risk of progressing from MCI to a diagnosis of Alzheimer's disease among participants on donepezil disappeared 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. Vitamin E had no effect at any time point in the study when compared with placebo.
Inflammation. There is evidence that inflammation in the brain may contribute to Alzheimer's disease damage. Some studies have suggested that drugs such as nonsteroidal anti-inflammatory drugs (NSAIDs) might help slow the progression of Alzheimer's disease, but clinical trials thus far have not demonstrated a benefit from these drugs. A clinical trial studying two of these drugs, rofecoxib (Vioxx) and naproxen (Aleve) showed that they did not delay the progression of Alzheimer's disease in people who already have the disease. Another trial, testing whether the NSAIDs celecoxib (Celebrex) and naproxen could prevent Alzheimer's disease in healthy older people at risk of the disease, has been suspended. However, investigators are continuing to follow the participants and are examining data regarding possible cardiovascular risk. Researchers are continuing to look for ways to test how other anti-inflammatory drugs might affect the development or progression of Alzheimer's disease.
Antioxidants. Several years ago, a clinical trial showed that vitamin E slowed the progress of some consequences of Alzheimer's disease by about 7 months. Additional studies are investigating whether antioxidants— vitamins E and C— can slow Alzheimer's disease. Another clinical trial is examining whether vitamin E and/or selenium supplements can prevent Alzheimer's disease or cognitive decline, and additional studies on other antioxidants are ongoing or being planned.
Ginkgo biloba. Early studies suggested that extracts from the leaves of the ginkgo biloba tree may be of some help in treating Alzheimer's disease symptoms. There is no evidence yet that ginkgo biloba will cure or prevent Alzheimer's disease, but scientists now are trying to find out in a clinical trial whether ginkgo biloba can delay cognitive decline or prevent dementia in older people.
Estrogen. Some studies have suggested that estrogen used by women to treat the symptoms of menopause also protects the brain. Experts also wondered whether using estrogen could reduce the risk of Alzheimer's disease or slow the disease. Clinical trials to test estrogen, however, have not shown that estrogen can slow the progression of already diagnosed Alzheimer's disease. One study found that women over the age of 65 who used estrogen with a progestin were at greater risk of dementia, including Alzheimer's disease, and that older women using only estrogen could also increase their chance of developing dementia.
Scientists believe that more research is needed to find out if estrogen may play some role in Alzheimer's disease. They would like to know whether starting estrogen therapy around the time of menopause, rather than at age 65 or older, will protect memory or prevent Alzheimer's disease.