Sometimes, you have to read between the lines.

As a columnist, I receive a host of press releases that fill up my mailbox with mostly unintelligible medical jargon which mostly amounts to nothing. So this past weekend, when I was sent a report from JAMA (Journal of the American Medical Association) saying that results from a six year study were being published in the following week’s journal, I eagerly awaited the study. However the study concluded that its six year evaluation on the effects of Ginkgo biloba extract on cognitive function in Alzheimer’s disease (AD) patients yielded nothing.

The study found no significant supporting evidence to say that Ginkgo biloba helped to prevent cognitive decline. Depressing, yes, but I had bigger fish to fry, and disregarded the report.

Imagine my surprise, when this morning, I check my email to find a press statement released by the American Botanical Council declaring that the exact same study pending publication in JAMA “supported” evidence that treatment with Gingko biloba helped stem symptoms of cognitive decline as well as “other uses.”


Ginkgo biloba has been used to prevent a variety of medical aliments, but whether it protects cognitive function from the decline of Alzheimer's is still vague. Photo credit: Oregon State University

Whoa, hold the phone. How can the same study yield two completely opposing statements?

The Ginkgo Evaluation of Memory (GEM) trial, scheduled for publication in JAMA on Wednesday November 19, showed that treatment with Ginkgo extract had no effect on prevention of cognitive decline in AD patients. The study evaluated 3,069 volunteers over the age of 75. In these participants, 2, 587 had normal cognition while 482 showed mild cognitive impairment, possibly signs of AD. During the six year trial, patients were evaluated ever six months and received either a placebo or a daily dose of Ginkgo biloba extract.

Overall, 523 participants in the clinical trial were diagnosed with dementia. 92% of these cases were categorized as possible AD, demonstrating evidence of damaged brain vasculature. Of those diagnosed with dementia, 246 patients were assigned to the placebo group while the other 277 patients were in the active group, receiving Ginkgo biloba treatment.

Overall, the total rate of dementia and possible AD did not differ between the two groups and treatment with Ginkgo had no significant effect on the rate of dementia progression in the patients with the initial mild cognitive impairment. Authors of the study conclude that “based on results of this trial, Ginkgo biloba cannot be recommended for the purpose of preventing dementia” (DeKosky ST, et. al.).

Patients who suffer from Alzheimer's have a breakdown of microtubules, which are support structures used for neurons in the brain. Tau proteins help to stabilize the microtubules and when tau is attacked during Alzheimer's, it is chemically altered, causing microtubule breakdown. This results in the decline of cognitive function in Alzheimer patients. Photo credit: FDA-Center for Devices and Radiologic Health

This seems pretty clear to me. Ginkgo is just not the answer for AD treatment. But the statement released by the American Botanical Council (ABC) would have you believe otherwise. Although the statement admits that the study found Gingko ineffective in preventing the development of dementia, it continues to find fault in the study itself, claiming that the study failed to demonstrate that Ginkgo was ineffective against dementia based on the parameters of the study itself.

In their statement, they cite that that the authors of the study acknowledge possible shortcomings of the trial due to its brevity. ABC quotes the authors in their statement saying that “Initial brain changes to clinical dementia are known to be long, it is possible that an effect of G. biloba, positive or negative, may take many more years to manifest” (DeKosky ST, et. al.)

Because the study took place over six years instead of 10 or 15, ABC claims that the benefits of treatment with Gingko biloba are still possible and more so, likely. Founder and executive director of ABC, Mark Blumenthal states “There is a significant body of scientific and clinical evidence supporting the safety and efficacy of Ginkgo extract for both cognitive function and improved circulation.”

Along with the claim that the trial was too short, they also cite that the trial lacked “active control,” in which medication with known efficacy was used to further evaluate the effects of the Ginkgo treatment on a scale with both poles fully defined. However, this is an impossible feat as no pharmaceutical drug had yet proven effective to prevent or delay progression of dementia. Among other reasons, ABC claims that this study should not be looked at as sole evidence, but alongside other clinical research being conducted on treatment with Gingko biloba. Their statement continues on to cite other research studies which saw positive results for Gingko treatment and others currently being conducted. But further research on the subject reveals that other studies have also concluded that Ginkgo treatment is ineffective for treatment of cognitive decline.

So what does this all mean? It means that even though dozens of studies have evaluated the effects of Ginkgo biloba, the results have still evaded a clear analysis. For every one study proving that treatment is effective for protecting cognition, another one proves that it is not. Even after all the results are in, scientists are still scratching their heads and ambivalent about Ginkgo treatment for delaying progression of AD.

It seems that the jury is still out on this ancient herbal remedy, and it is doubtful that a clear sentencing will ever be made. Overall, the body of research on Ginkgo biloba yields nebulous results, and seems to prove that another direction of research is the best answer to aid those suffering from AD.


References:

 DeKosky ST, Williamson J, Fitzpatrick A, Kronmal RA, Ives DG, Saxton J, Lopez O, Burke G, Carlson M, Fried L, Kuller LH, Robbins J, Tracy RP, Woolard NF, Dunn L, Snitz BE, Nahin RL, Furberg CD for the GEM Study Investigators. Ginkgo biloba for primary prevention of dementia: Results of the Ginkgo Evaluation of Memory (GEM) Study. JAMA Nov 19, 2008;300(19):2253-2262.

American Medical Association. Ginkgo biloba does not appear to prevent dementia, Alzheimer's disease [press release]. Chicago, IL: Nov. 13, 2008.

American Botanical Council. Ginkgo's Benefits for Treatment of Symptoms of Cognitive Decline and Other Uses Are Supported by Scientific Research [press release]. Austin, TX. Nov. 17, 2008.

Dodge HH, Zitzelberger T, Oken BS, Howieson D, Kaye J. A randomized placebo-controlled trial of Ginkgo biloba for the prevention of cognitive decline. Neurology 2008;70:1809-1817.