Nov. 19, 2008 The medicinal herb Ginkgo biloba does not reduce the risk of dementia or Alzheimer's disease development in either the healthy elderly or those with mild cognitive impairment, according to a large multicenter trial led by researchers at the University of Pittsburgh School of Medicine.
Findings from the Ginkgo Evaluation of Memory (GEM) Study, which is the first to have the necessary participant numbers and monitoring years to enable measurement of G. biloba's effectiveness and safety profile in dementia prevention, were just published in the Journal of the American Medical Association.
Dementia, especially Alzheimer's disease (AD), is a prevalent chronic disease currently affecting more than 5 million people in the United States and is a leading cause of age-related disability and long-term care placement, according to background information in the article. Ginkgo biloba is prescribed in some areas of the world for preservation of memory; however, there are no medications approved for prevention of dementia.
"Despite early indications that Ginkgo biloba has antioxidant and other properties that might preserve memory, this trial shows that, in fact, it has no impact on development of dementia and Alzheimer's Disease," said Steven T. DeKosky, M.D., principal investigator of the multi-center trial. Dr. DeKosky was director of the University of Pittsburgh Alzheimer's Disease Research Center and Chair of the Department of Neurology at the time the study was conducted. He now is Vice President and Dean of the University of Virginia School of Medicine.
G. biloba didn't affect the rate of coronary heart disease or stroke, either, the researchers found.
It's possible that an effect would have been observed, if the study had gone on longer, because it takes many years to progress from initial brain changes to clinical dementia, Dr. DeKosky noted. Therefore, the research team intends to conduct a follow-up analysis of brain function and structure in a subset of participants using magnetic resonance imaging.
In the study, which was conducted at five medical centers between 2000 and 2008, 3,069 people age 75 or older who had no, or mild, cognitive impairment were randomly assigned to take twice-daily doses of either 120 milligrams of G. biloba extract or a placebo. They were reassessed every six months for dementia using several well-established mental status tests. If changes were found that exceeded the expected "normal" changes in aging, a more extensive evaluation, including neuroimaging, was performed.
The researchers found no statistical difference in dementia or Alzheimer's disease rates between the groups. Among those taking G. biloba, 277 developed dementia. Among those in the placebo group, 246 developed dementia. Mortality rates also were similar.
"Studies of this magnitude are never possible without the selflessness of dedicated study participants. They continue to amaze us with their dedication to help find ways to prevent dementia and Alzheimer's disease," said Dr. DeKosky.
Other study sites included Johns Hopkins University, University of California-Davis, and Wake Forest University. Data management and statistical analyses were performed at the University of Washington in Seattle. Principal investigator of the University of Pittsburgh site was Lewis H. Kuller, M.D., Dr. P.H., University Professor of Public Health, Department of Epidemiology, Graduate School of Public Health.
A similarly-sized trial assessing the effectiveness of G. biloba is underway in Europe.
The trial was funded by the National Center for Complementary and Alternative Medicine and the National Institute on Aging, with support from the National Heart, Lung, and Blood Institute.
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The above story is based on materials provided by University of Pittsburgh Schools of the Health Sciences, via EurekAlert!, a service of AAAS.
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- DeKosky et al. Ginkgo biloba for Prevention of Dementia. JAMA, 2008;300(19):2253-2262 [link]
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