|Ginkgo Evaluation of Memory (GEM) Study
Fails To Show Benefit in Preventing Dementia in the Elderly
The dietary supplement Ginkgo biloba was found to be ineffective
in reducing the development of dementia and Alzheimer's disease
in older people, according to a study published in the Journal
of the American Medical Association1.
Researchers led by Steven T. DeKosky, M.D., formerly of the University
of Pittsburgh, vice president and dean of the School of Medicine
at the University of Virginia in Charlottesville, conducted the
trial known as the Ginkgo Evaluation of Memory (GEM) study at four
clinical sites over the course of 8 years. GEM is the largest clinical
trial ever to evaluate ginkgo's effect on the occurrence of dementia.
This research was co-funded by five components of the National
Institutes of Health (NIH): National Center for Complementary and
Alternative Medicine (NCCAM); National Institute on Aging (NIA);
National Heart, Lung, and Blood Institute; National Institute of
Neurological Disorders and Stroke, and the Office of Dietary Supplements.
"We have made enormous progress in understanding the basic mechanisms
involved in Alzheimer's disease, and we continue to pursue a vigorous
program to translate what we know into the development and testing
of new potential therapies for this devastating disease," said
Richard Hodes, M.D., director of the NIA. "However, it is disappointing
that the dietary supplement tested in this study had no effect
in preventing Alzheimer's disease."
GEM enrolled 3,069 participants age 75 or older with normal cognition
or mild cognitive impairment. Those with dementia were excluded
from participation. After extensive medical and neuropsychological
screening, participants were randomly assigned to receive twice-daily
doses of either 120 milligrams of ginkgo extract or an identical-appearing
placebo. The 240 milligrams daily dose of ginkgo was selected based
on current dosage recommendations and prior clinical studies indicating
possible effectiveness at this dose. The products used in the study
were supplied by Schwabe Pharmaceuticals, a German company.
"According to the 2007 National Health Interview Survey, ginkgo
is one of the top 10 natural products used by Americans," said
Richard L. Nahin, Ph.D., M.P.H., acting director of the Division
of Extramural Research at NCCAM. "It is important to conduct studies
and build the scientific evidence base regarding botanical supplements
through rigorous research, such as the GEM trial."
The study was conducted primarily to determine if ginkgo would
decrease the incidence of all types of dementia and, more specifically,
reduce the incidence of Alzheimer's disease. Secondarily, the study
evaluated ginkgo for its effects on overall cognitive decline,
functional disability, incidence of cardiovascular disease and
stroke, and total mortality. The primary endpoint was the diagnosis
of dementia as determined by an expert panel of clinicians using
standard criteria for diagnosis. The patients with a diagnosis
of dementia underwent magnetic resonance imaging scans to determine
their dementia type.
"The results of this study confirm the importance of randomized
trials in the development of new therapies for dementia and Alzheimer's
disease and in determining therapeutic benefit not only for conventional
therapies but also complementary therapies like ginkgo," said Dr.
DeKosky, principal investigator on the GEM study. "If older patients
are considering using ginkgo for preventing dementia, I urge them
to speak with their health care providers about the results of
this study and work together to create the best treatment plan."
Study participants were followed for an average of approximately
6 years (maximum of just over 7 years). During the study, 523 participants
were diagnosed with dementia, 246 in the placebo group and 277
in the ginkgo group. Thus, ginkgo showed no overall effect for
reducing all types of dementia or Alzheimer's disease. In addition,
in analyzing safety data, the GEM study did not find significant
adverse effects from ginkgo, in particular there was no evidence
for increased bleeding risk in persons taking ginkgo.
Cognitive status was known for more than 93 percent of all participants
at the end of the trial and 60 percent of active participants were
taking their assigned study medication. There was no difference
in adherence to taking medication between the ginkgo group and
the placebo group.
"While this study revealed that ginkgo does not have an effect
on reducing dementia in the study populationit does provide us
with important information about how to design and conduct large
dementia prevention trials in older adults" said Dr. Jeff Williamson,
a geriatrician and principal investigator of the GEM Clinical Coordinating
Center at Wake Forest University. "Future analyses will provide
us with additional information on ginkgo's possible effects on
cardiovascular disease, cancer, depression and other age-related
conditions. We are especially grateful to the more than 3,000 older
adults who dedicated many hours to helping us answer the important
questions addressed by GEMS."
The GEM results will prove useful in determining how many participants
are needed in future trials to provide clinically significant measures
on outcomes such as occurrence of dementia. Future analysis of
this study may also identify subgroups of these participants who
may be at greater risk for developing dementia.
Data analysis for the trial was overseen by the University of
Washington, Seattle and the four GEM institutions that participated
in this study were
- University of Pittsburgh
- Wake Forest University, Winston-Salem, N.C.
- Johns Hopkins University, Baltimore, Md.
- University of California, Davis
The National Center for Complementary and Alternative Medicine's
mission is to explore complementary and alternative medical practices
in the context of rigorous science, train CAM researchers, and
disseminate authoritative information to the public and professionals.
For additional information, call NCCAM's Clearinghouse toll free
at 1-888-644-6226, or visit the NCCAM Web site at www.nccam.nih.gov.
The National Institutes of Health (NIH) — The Nation's
Medical Research Agency — includes 27 Institutes and Centers
and is a component of the U.S. Department of Health and Human Services.
It is the primary federal agency for conducting and supporting basic,
clinical and translational medical research, and it investigates
the causes, treatments, and cures for both common and rare diseases.
For more information about NIH and its programs, visit www.nih.gov.
 DeKosky ST, Williamson JD, Fitzpatrick AL, et al. Ginkgo
biloba for Prevention of Dementia. Journal of
the American Medical Association.
2008 300(19): 2253-2262.