MINNEAPOLIS, November 20, 2008—Ginkgo biloba, an herbal extract thought by many to sharpen mental faculties, was found to be ineffective in preventing or delaying dementia or Alzheimer’s disease, in a major independent clinical trial.

The research, involving thousands of volunteers between the ages of 75 and 96, was the first study broad enough to assess the plant extract’s effect on the incidence of dementia.

The results conclusively extinguished optimism that the drug was useful in preventing or treating dementia. Indeed, in the study, participants who took ginkgo biloba experienced a greater incidence of dementia and Alzheimer's.

Ginkgo is one of the top-selling herbal supplements, used by people with the aim of improving memory and cognition and other purposes. Defenders of the extract reminded reporters at the Los Angeles Times that no conventional treatment for dementia has shown positive results, either.

People taking part in the study entered with no cognitive problems or only mild impairment. Eighteen percent in the ginkgo group and 16 percent in the placebo group were diagnosed with Alzheimer's or other dementia during the study.

Results of the study appeared in the Journal of the American Medical Association.

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