Ginkgo Shows No Effect on Cognitive Decline

CHICAGOOlder adults who used ginkgo biloba for several years did not see a reduction in cognitive decline compared to adults who received placebo in  the largest randomized controlled trial of ginkgo to date (JAMA. 2009;302[24]:2663-2670). However, the American Botanical Council (ABC) and the Council for Responsible Nutrition (CRN) both responded to the study, saying it does not prove the botanical isnt effective.

Researchers analyzed older adults who had normal cognition or mild cognitive impairment (MCI) in the Ginkgo Evaluation of Memory (GEM) study. The GEM study previously found ginkgo was not effective in reducing the incidence of Alzheimer dementia or dementia overall. The randomized, double-blind, placebo-controlled clinical trial included 3,069 community-dwelling participants, ages 72 to 96 years, who received a twice-daily dose of 120-mg extract of ginkgo (n = 1,545) or identical-appearing placebo (n = 1,524). The study was conducted at six academic medical centers in the United States between 2000 and 2008, with a median follow-up of 6.1 years. Change in cognition was assessed by various tests and measures.

Researchers found no evidence for an effect of ginkgo on global cognitive change and no evidence of effect on specific cognitive domains of memory, language, attention, visuospatial abilities and executive functions. They also found no evidence for differences in treatment effects by age, sex, race, education or baseline cognitive status.

In response to the study, ABC questioned the studys validity. ABC states the study is limited and the public should focus on the well-documented cognitive and cardiovascular benefits of ginkgo. There are many significant limitations of this study, said Mark Blumenthal, ABC founder and executive director.

In a press release, ABC said the trials results may be inaccurate for a number of reasons. First, they said, the data being published this week are drawn from a previous clinical trial, which was not designed to determine the decline in cognition. Second, about 40 percent of the subjects dropped out over the six-year duration of the trial; the statistics reported in the study include the dropouts for which no final data are available. Further, the subjects in the study were not monitored for certain cognitive parameters until several years after the trial began, creating difficulty in determining accurately whether they experienced a decline in cognition or not. Also, the age of the subjects is quite advanced, at an average of 79 years at the beginning of the trial. ABC said this age group is not typical of the age of both healthy people and those with mild cognitive impairment who use ginkgo for improving mental performance.

Further, ABC noted that another weakness of this trial is the lack of an active control, i.e., a potential third arm of the trial (i.e., besides the patients on ginkgo or placebo) in which patients would have used a pharmaceutical medication with presumed efficacy, to determine to what extent the particular population being tested would respond. This was not possible for this trial since no conventional pharmaceutical drug has ever demonstrated the ability to prevent the onset of dementia or diminish its progression.

Also in response to the study, Douglas MacKay, N.D., vice president, scientific and regulatory affairs, CRN, said it should be viewed in context to the a large body of previously published evidence suggesting that Ginkgo biloba may help improve cognitive impairment in older adults. He noted ongoing clinical trials may address some of the limitations of the current study. The results of this single study add to the overall data on Ginkgo biloba, including valuable evidence in support of Ginkgos safety profile, but should not be viewed as the final word, he said. In addition, several studies have demonstrated that Ginkgo biloba can be used to improve blood circulation and reduce oxidative stress, two risk factors associated with the progression of cognitive decline, dementia and Alzheimers disease.

Mackay further noted he hopes this study doesnt send the wrong message to consumers. I would continue to recommend Ginkgo biloba to older adults as a safe, effective option for supporting cognitive health and would encourage consumers to talk to their own healthcare professional about what is right for them.