MONDAY, July 19, 2004 (HealthDayNews) -- A drug used to treat mild to moderate Alzheimer's disease may slow down development of the less severe forms of cognitive impairment that sometimes lead to the more devastating brain condition.
Patients with mild cognitive impairment (MCI) who took donepezil (brand name Aricept) had a lower risk of developing Alzheimer's compared to people taking a placebo, according to research presented at the International Conference on Alzheimer's Disease and Related Disorders being held in Philadelphia from July 17 to 22.
The reduction in risk lasted only for the first 18 months of the three-year trial, however. When those taking donepezil did develop Alzheimer's, it was an average of six months later than those in the placebo group.
MCI can be a sort of border region between the normal cognitive changes of aging and Alzheimer's disease. Not everyone with MCI goes on to have Alzheimer's disease or another dementia.
It's now unclear which people with MCI will go on to develop a dementia such as Alzheimer's. "What we want to do is predict who will progress to dementia or Alzheimer's," said Dr. Claudia Kawas, a professor of neurology at the University of California, Irvine College of Medicine, who moderated a news conference announcing these preliminary results. "The problem now is I can't predict."
The study authors looked specifically at people exhibiting one form of MCI, amnestic MCI, in which memory is significantly impaired but other functions remain relatively normal. None of the study participants had dementia.
Almost 800 individuals were randomly assigned to one of three groups: to receive 2,000 international units (IUs) daily of vitamin E; to receive 10 milligrams of Aricept a day; or to receive a placebo. All participants also received a multivitamin and were evaluated every six months for three years.
Those in the vitamin E and placebo groups progressed to Alzheimer's at about the same rate. Those taking donepezil, however, did not progress as rapidly for the first 18 months of the study. At this midpoint, 54 people in the placebo group and 50 in the vitamin E group had transitioned to Alzheimer's, while only 30 in the donepezil group had progressed, said Dr. Ronald Petersen of the Mayo Clinic, who is a principal investigator in the National Institute of Aging-funded study.
By three years, however, the rates had effectively converged. "The donepezil group caught up in the last half of the study, but it seemed like there was some activity in the first half of the trial," Petersen said. "We concluded that neither vitamin E nor donepezil had an overall effect over the entire 36 months but donepezil reduced risk for the first 18 months."
The data is consistent with what experts already know about this class of drugs, cholinesterase inhibitors, which is that they have an effect on symptoms but do not affect the underlying disease process, said William Thies, vice president of medical and scientific affairs at the Alzheimer's Association.
"It's not prevention, but we may be able to intervene at an earlier stage," Petersen echoed. "We need better therapeutic interventions to address the underlying causes of Alzheimer's."
A number of questions remain unanswered, including why the benefit appears to end at 18 months, whether there is a specific window of opportunity during which these drugs work, whether the observed slowdown holds throughout the course of Alzheimer's in people who go on to develop it, and whether the drug has any promise for actual prevention.
The study is also unlikely to result in any changes, sweeping or otherwise, to clinical recommendations. "This is just one study," Kawas said. "In general, recommendations for clinical practices come out of several studies."
This doesn't mean, however, that individual physicians won't incorporate some of this information. "We have to separate the public health implications vs. the practice of medicine," Thies said. "Individual physicians will incorporate data when talking to patients, but it won't be across the board."
Thies also speculated that the lack of improvement seen in the vitamin E group won't dissuade others from using the compound. "Other studies say it has been useful, and this is a disease for which we don't have many options," he said.
The Alzheimer's Association has more on cholinesterase inhibitors and other drugs for this disease.