National Institute on Aging (NIA)
The University of Pittsburgh School of Medicine was awarded a six year cooperative agreement (an assistance mechanism in which the NIH will have substantial involvement with the recipient during the performance of the planned activity) totaling $15 million to coordinate a multicenter effort to study the effectiveness of ginkgo biloba extract in preventing dementia in older individuals. Steven T. DeKosky, M.D., Professor of Psychiatry, Neurology and Neurobiology, and Director of the Alzheimer's Disease Research Center at the University of Pittsburgh School of Medicine will serve as the principal investigator of this study. Data collection and analysis of the four study sites will be coordinated by the University of Washington, Seattle, WA.
The four clinical study centers include:
"These centers will test the efficacy, safety, and tolerability of an extract of ginkgo biloba in preventing dementia in aging individuals. Our goal is to advance scientific knowledge about this substance's effectiveness in preventing dementia and improving quality of life," said William R. Harlan, M.D., acting director of the NCCAM.
The six-year study will enroll a total of 2,000 participants, who will be randomly assigned to one of two groups. Study participants who will take 240 mg. of ginkgo biloba will be compared to a second group of individuals who will take a placebo. Approximately 1500 study participants will be recruited from current Cardiovascular Health Study participants who made a clinic visit in 1998-99. The study will enroll the remaining 500 participants in about six months. The primary outcome of this study will be the onset of any type of dementia. The secondary outcome will be measured by changes in cognitive function.
The term dementia describes a group of symptoms that are caused by changes in brain function and is rare in those less than 60 years of age. Surveys indicate that one-third of Americans over the age of 85 suffer from some kind of dementia (Alzheimer's disease, vascular dementia or mixed types), with about four million Americans in this age group suffering from Alzheimer's disease alone. The incidence of dementia approximately doubles every five years after age 65, and nearly half of all people age 85 and older are thought to have some form of dementia.
Symptoms of dementia may include asking the same questions repeatedly; becoming lost in familiar places; inability to follow directions; becoming disoriented about time, people, and places; and neglecting personal safety, hygiene, and nutrition. People with dementia experience a gradual reduction in mental or intellectual functions, especially memory and generally lose these functions at different stages of the disease. The two most common forms of dementia in older people are Alzheimer's disease and multi-infarct dementia (sometimes called vascular dementia). These types of dementia are irreversible, which means they cannot be cured. Dementia can often lead to the need for long-term care of patients and enormous financial and emotional burdens for families.
For centuries, extracts from the leaves of the ginkgo biloba tree have been used as Chinese herbal medicine to treat a variety of medical conditions. In Europe and some Asian countries, standardized extracts from ginkgo leaves are routinely taken to treat a wide range of symptoms, including Alzheimer's disease.
The first clinical study of ginkgo biloba and dementia in the United States was conducted by researchers at the New York Institute for Medical Research in Tarrytown, New York. These scientists examined how taking 120 mg a day of a ginkgo biloba extract affected the rate of cognitive decline in older individuals with mild to moderately severe dementia due to Alzheimer's disease and vascular dementia. The results of this study were published in the Journal of the American Medical Association (October 22/29, 1997), and suggest that a ginkgo biloba extract may be of some help in treating symptoms of Alzheimer's disease and vascular dementia.
Many different preparations of ginkgo biloba extract are available over the counter; however, they vary in content and active ingredients. Because not enough research has been done, no specific daily amount of ginkgo biloba extract can be recommended as safe or effective at this time. In addition, no evidence exists to suggest that ginkgo biloba can either cure or prevent Alzheimer's disease. In fact, some recent case studies imply that daily use of ginkgo biloba extracts may cause side effects, such as excessive bleeding, especially when combined with daily use of aspirin.
"In light of recent studies that indicate dangerous side effects when combined with aspirin or other prescription medications and without clear or compelling evidence of its effectiveness, people should consult with their primary doctor before using ginkgo biloba to treat any serious health condition," concluded Dr. William R. Harlan.
The National Institute on Aging (NIA) is the lead federal agency supporting and conducting Alzheimer's disease research, including studies of the basic, clinical, and epidemiological aspects of this and other related dementias of aging. For more information, contact NIA's Alzheimer's Disease Education & Referral (ADEAR) Center at 1-800-438-4380 or visit its website at http://www.alzheimers.org.