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Ginkgo biloba for the Evaluation of Memory (GEM) Study


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About the Study

What is the Ginkgo biloba for the Evaluation of Memory (GEM) study?

The GEM study is the largest clinical trial ever to evaluate the effects of the dietary supplement Ginkgo biloba on the occurrence of dementia. The study tested the effectiveness of 120 milligrams of ginkgo twice daily versus placebo in lowering the incidence of dementia, in general, and Alzheimer's disease (AD), specifically, in normal elderly people and those with mild cognitive impairment (MCI).

Researchers led by Steven T. DeKosky, M.D., formerly of the University of Pittsburgh, now Vice President and Dean of the School of Medicine at the University of Virginia in Charlottesville, conducted the 8-year study at four clinical sites. This research was co-funded by five components of the National Institutes of Health (NIH): National Center for Complementary and Integrative Health (NCCIH); National Institute on Aging; National Heart, Lung, and Blood Institute; National Institute of Neurological Disorders and Stroke, and the Office of Dietary Supplements.

What was the purpose of the study?

Ginkgo is widely used for its potential positive effects on memory and cognition, and laboratory studies have shown several possible ways that ginkgo might work to produce these potential effects. To date, adequate clinical trials testing the effect of ginkgo on dementia incidence were lacking. The GEM study was designed to determine the ability of ginkgo to prevent or delay the onset of dementia, particularly Alzheimer's disease, in the elderly.

What was the basic design of the study?

In the GEM study, participants were randomly assigned to either a group that would take 120 milligrams twice daily of ginkgo or a group that would take an identically appearing placebo twice daily. To reduce the chance of biased results, the study was double-blinded—neither the researchers nor the participants knew which group the participants were in. The randomization was done separately for each clinical site using a computer-generated, randomly assigned list maintained at the Data Coordinating Center at the University of Washington in Seattle.

The study recruited and followed 3,069 elderly individuals for an average of 5.8 years on medication. The primary endpoint was the diagnosis of dementia using the Diagnostic Statistical Manual IV (DSM IV) criteria as determined by an expert panel of clinicians. The patients with a diagnosis of dementia underwent magnetic resonance imaging (MRI) scans to determine their dementia type.

What did the GEM Study cost?

The total cost for the GEM Study was approximately $36.5 million. This figure includes the costs of the clinical trial itself, the banking of blood specimens, and a number of ancillary studies that are still being conducted.


Study Background

What is dementia?

According to the National Institute on Aging (NIA), people who have serious changes in their memory, personality, and behavior may suffer from a form of brain disease called dementia, which can seriously affect a person's ability to carry out daily activities. The term dementia describes a group of symptoms that are caused by changes in brain function. Dementia is caused by many conditions; some conditions can be reversed, and others cannot. The two most common forms of dementia in older people are Alzheimer's disease and multi-infarct dementia (sometimes called vascular dementia or stroke).

What is Alzheimer's disease?

According to the NIA, Alzheimer's disease affects as many as 4.5 million Americans and is the most common form of dementia among older people, but it is not a normal part of aging. Alzheimer's disease is an irreversible, progressive brain disease that slowly destroys memory and thinking skills. Over time, the disease leads to the inability to carry out the simplest tasks of daily living and, eventually, causes death. In most people with Alzheimer's disease, symptoms first appear after age 60. Although treatment can slow the progression of Alzheimer's and help manage its symptoms in some people, currently there is no cure for the disease.

What is Ginkgo biloba?

Ginkgo biloba, commonly called ginkgo, is a botanical—a plant or plant part used for its scent, flavor, and/or therapeutic properties. The ginkgo tree is one of the oldest types of trees in the world, and ginkgo seeds have been used in traditional Chinese medicine for thousands of years. Ginkgo extracts are usually taken from the ginkgo leaf and are used to make tablets, capsules, or teas. Today, people use ginkgo leaf extracts hoping to improve memory; to treat or help prevent Alzheimer's disease and other types of dementia; to decrease intermittent claudication (leg pain caused by narrowing arteries); and to treat sexual dysfunction, multiple sclerosis, tinnitus, and other health conditions. In the United States, ginkgo is sold as a dietary supplement. For more information see Herbs at a Glance: Ginkgo.

What doses were used?

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 prior clinical study outcomes and a literature review of clinical trials that found 240 milligrams to be the most effective dose.

Who provided the products used in the study?

The products used in the study were supplied by Schwabe Pharmaceuticals, Germany, following a separate NCCIH request for a company to provide a ginkgo product with a consistent, pre-specified composition as well as placebo tablets that were identical to the ginkgo in appearance and packaging.

Where was the study conducted?

The University of Pittsburgh, Pittsburgh, PA, served as the coordinating study center and oversaw the research and recruitment efforts of the four centers. The study was led by Steven T. DeKosky, M.D., of the University of Pittsburgh, now Vice President and Dean of the School of Medicine at the University of Virginia, Charlottesville, VA. The Data Coordinating Center was at the University of Washington, Seattle, WA. The Cognitive Diagnostic Center was at the University of Pittsburgh. The Clinical Coordinating Center was at Wake Forest University School of Medicine, Winston-Salem, NC. The Central Laboratory was at the University of Vermont, Burlington, VT. The MRI Reading Center was at the University of Pittsburgh.

The four GEM clinical sites and their lead investigators were

  • University of Pittsburgh, Pittsburgh, PA; Lewis Kuller, M.D., Dr.P.H.,
  • Wake Forest University, Winston-Salem, NC; Gregory Burke, M.D.
  • Johns Hopkins University, Baltimore, MD; Michelle C. Carlson, Ph.D.
  • University of California-Davis, Davis, CA; John Robbins, M.D., M.H.S.


Key Results

What were the key results of the study?

Researchers found that:

  • In this study, ginkgo at 120 milligrams twice a day was neither effective in lowering the overall incidence rate of dementia nor Alzheimer's disease incidence in normal elderly or elderly people with mild cognitive impairment.
  • The study experience does demonstrate the feasibility of conducting large dementia prevention trials in older adults.

How many people participated in this study and who were they?

A total of 3,069 people participated in the study. Participants were age 75 or older with normal cognition or mild cognitive impairment. All participants were required to identify a proxy willing to be interviewed every 6 months at the time of each study visit. Persons with prevalent dementia were excluded from participation. Mean age at entry for all participants was 79.1 years and 46 percent of participants were women. The ginkgo and placebo groups were similar in their baseline characteristics.

Were there side effects from Ginkgo biloba?

The study did not find significant side effects from ginkgo, in particular there was no evidence for increased bleeding risk in persons assigned to ginkgo.


Consumer Information and Next Steps

Should people use Ginkgo biloba to prevent dementia?

People with dementia should work with their health care provider to develop a comprehensive treatment plan. The results of this study show that 120 milligrams of ginkgo twice a day does not prevent the onset of dementia in older people.

Can U.S. consumers get the Ginkgo biloba product used in the GEM study?

The ginkgo product used in this trial is available commercially in the United States under the brand name Ginkgold Max, under the label Nature's Way.


For More Information

NCCIH Clearinghouse

The NCCIH Clearinghouse provides information on NCCIH and complementary and integrative health approaches, including publications and searches of Federal databases of scientific and medical literature. The Clearinghouse does not provide medical advice, treatment recommendations, or referrals to practitioners.

Toll-free in the U.S.: 
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National Heart, Lung, and Blood Institute (NHLBI)

The NHLBI Health Information Center provides information to health professionals, patients, and the public about heart, lung, and blood diseases and sleep disorders and accepts orders for publications.

P.O. Box 30105
Bethesda, MD 20824-0105
Phone: 301-592-8573, or dial 7-1-1 for access to free Telecommunications Relay Services (TRS)

National Institute on Aging (NIA)

NIA is the NIH institute that focuses on supporting and conducting high-quality research on aging processes, age-related diseases, and special problems and needs of the aged. NIA publications include Hormones and Menopause: Tips from the National Institute on Aging.

National Institute of Neurological Disorders and Stroke (NINDS)

NINDS conducts and supports research on how the brain and nervous system function and on treatments for neurological diseases.

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Office of Dietary Supplements (ODS), National Institutes of Health (NIH)

ODS seeks to strengthen knowledge and understanding of dietary supplements by evaluating scientific information, supporting research, sharing research results, and educating the public. Its resources include publications (such as Dietary Supplements: What You Need to Know), fact sheets on a variety of specific supplement ingredients and products (such as vitamin D and multivitamin/mineral supplements), and the PubMed Dietary Supplement Subset.


U.S. Food and Drug Administration (FDA)

The FDA oversees the safety of many products, such as foods, medicines, dietary supplements, medical devices, and cosmetics. See its webpage on Dietary Supplements.

Toll-free in the U.S.: 

This page last modified September 24, 2017