Ginkgo Biloba Does Not Cut Dementia Risk, Pitt-led Study Finds

Issue Date: 
December 1, 2008


The medicinal herb Ginkgo biloba does not reduce the risk of dementia or Alzheimer’s disease developing in either the healthy elderly or those with mild cognitive impairment, according to a large multicenter trial led by researchers in the University of Pittsburgh School of Medicine.

Findings from the Ginkgo Evaluation of Memory (GEM) Study were published in the Nov. 18 Journal of the American Medical Association. The study is the first such study to have the necessary participant numbers and monitoring years to enable measurement of Ginkgo biloba’s effectiveness and safety profile in dementia prevention.

“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 the development of dementia and Alzheimer’s disease,” said Steven T. DeKosky, principal investigator of the multicenter trial. 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.

Ginkgo biloba also didn’t affect the rate of coronary heart disease or stroke, the researchers found.

It’s possible that an effect would have been observed if the study had continued, because it takes many years to progress from initial brain changes to clinical dementia, 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 Ginkgo 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 Ginkgo 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 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, University Professor of Public Health, Department of Epidemiology, Pitt’s Graduate School of Public Health.

A similar-size trial assessing the effectiveness of Ginkgo biloba is under way 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