A federally funded study that appears in the Nov. 19 Journal of the American Medical Association (JAMA) concludes that Ginkgo biloba was ineffective in preventing dementia.

This randomized, double-blind, placebo-controlled clinical trial conducted in five academic medical centers in the U.S. between 2000 and 2008 evaluated 3069 community volunteers aged 75 years or older with normal cognition (n = 2587) or MCI [Mild Cognitive Impairment] (n = 482). Study subjects were assessed every six months for incident dementia.

Participants received 120 mg of Ginkgo biloba extract (n = 1545) or placebo (n = 1524) twice daily over a median period of six years.

Results indicate 523 individuals developed dementia (246 receiving placebo and 277 receiving Ginkgo biloba) with 92% of the dementia cases classified as possible or probable Alzheimer’s disease (AD) or AD with evidence of vascular disease of the brain.

Rates of dropout and loss to follow-up were low (6.3%), and the adverse effect profiles were similar for both groups.

Funded by the National Institutes of Health’s National Center for Complementary and Alternative Medicine, the study represents the largest randomized trial of a botanical medicine ever conducted, according to the agency.

However, the trial did not test whether or not Ginkgo biloba serves to prevent dementia, or if it improves thinking and memory in the short term.

“This study is not irrelevant, but it cannot be used to make broad conclusions about Ginkgo biloba and the general population,” noted Daniel Fabricant, PhD, vice president for scientific and regulatory affairs at the Natural Products Association, Washington, D.C. “In fact, it misses the boat entirely in two critical areas. One, it looks exclusively at people almost 80 years old who are far more likely to have Alzheimer’s, while ignoring those in middle ages, where the risk for developing the disease rises quickly and prevention could best be analyzed. Two, it excludes completely any consideration of the strong and established role that family history plays with Alzheimer’s. You can’t do a study on the weather without looking at wind and rain.”

Mr. Fabricant went on to say that this study is in direct contrast to previous research. “Unfortunately, there is still no proven treatment to prevent Alzheimer’s, but reputable research has shown that Ginkgo biloba can play a constructive role in improving the symptoms related to this debilitating disease and possibly delaying its onset.”

Michael McGuffin, president, American Herbal Products Association, Silver Spring, MD, agreed, saying, “The study does not in any way undermine what has already been observed with regard to the usefulness of Ginkgo extract, and EGb 761 in particular, in providing symptomatic relief in persons who already suffer from dementia or Alzheimer’s disease. In fact, Ginkgo extract has been shown to work as well as the available approved drugs to slow the progression of Alzheimer’s disease.”