Alzheimer's Study Blasts Ginkgo, Industry Fires Back

Alzheimer's Study Blasts Ginkgo, Industry Fires BackA study published in the Nov. 19 issue of JAMA (2008;300(19):2253-2262) concluded  the use of Ginkgo biloba, claimed to have beneficial effects on memory and cognition, was not effective in reducing the rate of dementia or Alzheimer’s disease among more than 1,500 elderly study participants after several years of use. Dementia, especially Alzheimer’s disease (AD), is a prevalent chronic disease currently affecting more than 5 million people in the United States and is a leading cause of age-related disability and long-term care placement, according to background information in the article. Ginkgo biloba is prescribed in some areas of the world for preservation of memory; however, the study authors contend there are no medications approved for prevention of dementia, and to date, no clinical trial of adequate design and size has evaluated the safety and effectiveness of Ginkgo biloba in the primary prevention of dementia. Steven T. DeKosky, M.D., of the University of Pittsburgh, Pa., and the Ginkgo Evaluation of Memory (GEM) Study Investigators assessed the effectiveness of Ginkgo biloba in dementia prevention. The study was a randomized, placebo-controlled clinical trial conducted at five academic medical centers in the United States between 2000 and 2008 with a median (midpoint) follow-up of 6.1 years. The trial included 3,069 community volunteers age 75 years or older with normal cognition (n=2,587) or mild cognitive impairment (MCI; n=482) at study entry, who were assessed every six months for dementia. Participants were randomized to receive either a twice-daily dose of 120 mg extract of Ginkgo biloba (n=1,545) or placebo (n=1,524).The researchers found during the intervention period, 523 participants were diagnosed with dementia, 246 (16.1 percent) in the placebo group and 277 (17.9 percent) in the Ginkgo biloba group. Of the total dementia cases, 92 percent were classified as possible or probable AD or AD with evidence of vascular disease of the brain. The rate of total dementia did not differ between participants assigned to Ginkgo biloba vs. placebo (3.3 dementia cases/100 persons, per year exposed, among persons randomized to Ginkgo biloba vs. 2.9/100 persons, per year exposed, among persons randomized to placebo). The rate of Alzheimer-type dementia also did not differ between the two treatment groups (3.0/100 persons, per year exposed vs. 2.6/100 persons, per year exposed). Ginkgo biloba also had no effect on the rate of progression to dementia in participants with MCI.The adverse event profiles for Ginkgo biloba and placebo were similar and there were no statistically significant differences in the rate of serious adverse events.“Based on the results of this trial, Ginkgo biloba cannot be recommended for the purpose of preventing dementia,” the authors wrote. “These results confirm randomized trials remain critical to the spectrum of translational research necessary to develop new therapies and to determine whether the purported in-vitro, epidemiologic and surrogate measures of therapeutic benefit are true, not only for traditional pharmaceutical therapies, but also for complementary therapies. Of almost equal importance from these results is the provision of a strong rationale for including older individuals in randomized trials testing promising interventions for preventing or delaying dementia onset.”The herbal products industry was quick to take issue with the JAMA study and its authors. “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,” said Michael McGuffin, president of the American Herbal Products Association (AHPA). “In fact, Ginkgo extract has been shown to work as well as the available approved drugs to slow the progression of Alzheimer’s disease.”The Natural Products Association (NPA) agreed there is a long trail of research showing benefits from Ginkgo extract in this area of mental wellness. They said the study failed to investigate this herb properly and is too limited to draw meaningful conclusions about the breadth of health benefits Ginkgo offers.“This study is not irrelevant, but it can not be used to make broad conclusions about Ginkgo biloba and the general population. In fact, it misses the boat entirely in two critical areas," said Daniel Fabricant, Ph.D., vice president for scientific and regulatory affairs at NPA. "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."Fabricant added the JAMA study is in direct contrast to other 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.”