If avoiding Alzheimer's is one of your priorities, you might consider
discarding your ginkgo tablets and enrolling in a continuing medical education
Many Americans believe that use of the herb Ginkgo biloba can help
stave off development of Alzheimer's disease. However, results from a large
clinical trial are sure to disappoint ginkgo proponents.
The trial, headed by Steven DeKosky, M.D., of the University of Virginia
and a leading Alzheimer's scientist, was conducted at five academic medical
centers throughout the United States. It included more than 3,000 community
volunteers aged 75 or older with either normal cognition or mild cognitive
impairment. It used a randomized, placebo-controlled, double-blind design.FIG1
Half the subjects took 120 mg of ginkgo twice a day, and half took a
placebo twice a day. Subjects were evaluated every six months for dementia
over the following six years. At the end of the six years, 523 subjects had
developed dementia—277 in the ginkgo group and 246 in the placebo
Moreover, when the researchers looked to see whether ginkgo might have had
an effect on just the incidence of Alzheimer's, not on the incidence of
various types of dementia, they still failed to find a preventive effect for
gingko, they concluded.
The study was published in the November 19, 2008, Journal of the
American Medical Association.
One strength of the study was that the Gingko biloba extract
tested was a standardized formulation with specific amounts of active
ingredients—in fact, the world's most clinically tested gingko extract.
One weakness of the study was that only subjects 75 years of age or older were
used. So it is still possible that ginkgo might be able to prevent Alzheimer's
if people start taking it earlier in their lives, DeKosky and his group
Even if that is not the case, ginkgo may well counter symptoms of
Alzheimer's, Hyla Cass, M.D., a psychiatrist in Pacific Palisades, Calif., and
an authority on alternative and complementary medicine, told Psychiatric
News. “There are compelling data showing [its] benefits ... in
treating symptoms of dementia....”
For instance, in one randomized, placebo-controlled, double-blind trial,
ginkgo was found to be as effective as donepezil in treating Alzheimer's.
Donepezil is one of the drugs approved by the Food and Drug Administration for
Further, 11 clinical trials have suggested that ginkgo can improve the
attention, memory, and cognitive speed of healthy, cognitively intact
subjects, Cass pointed out. So even if ginkgo cannot halt the development or
progression of Alzheimer's, it may still enhance mental processes in people
without the disease, she said.
Meanwhile, somewhat more encouraging news on the Alzheimer's prevention
front was published by Norwegian researchers in the November 2008
International Journal of Geriatric Psychiatry—that education
may be able to offset people's genetic liability for Alzheimer's. The major
investigator was Sigrid Sando, M.D., Ph.D., a consultant neurologist at St.
Olav's Hospital in Trondheim.
Education might protect against Alzheimer's, some past studies have
suggested. The apolipoprotein E (APOE) e4 gene variant is one of the strongest
documented risk factors for Alzheimer's. Sando and her coworkers investigated
whether the level of education that people have attained might offset any e4
gene variant vulnerability for Alzheimer's that they possess.
Their case-control study included 373 subjects with Alzheimer's and 559
healthy controls. They evaluated all of the subjects for the types of APOE
gene variants they possessed. Not surprisingly, they found that the chances of
developing Alzheimer's were 4.4 times greater for persons with one e4 variant
than for persons without such a variant, and that the chances were 13.1 times
greater for persons with two e4 variants than for persons without such a
Even if subjects had one or two e4 variants, their odds of getting
Alzheimer's were significantly less if they had achieved a higher level of
education (eight to nine years) than if they had achieved only a lower one
(six to seven years). What's more, the protective effect seemed to exist in a
dose-dependent manner—those with 10 to 18 years of education were even
better protected than those with eight to nine years of education. Thus, even
if the APOE e4 gene variant is present, a greater amount of education can help
protect against Alzheimer's, Sando and her group concluded in their
Education may offer protection directly, Sando and her team
speculated—for example, it is possible that a brain that has been
challenged by education is better able to fight off brain pathology than is a
brain less educationally challenged. Or it may be a proxy for some other
protective factor—say, good nutrition or good socioeconomic conditions
The gingko study was financed by the National Center for Complementary and
Alternative Medicine, the National Institute on Aging, and several other
institutes and offices. Schwabe Pharmaceuticals in Germany donated the gingko
tablets and identical placebos in blister packs for the study. The education
study was funded by the National Institutes of Health and the Research Council
An abstract of “Ginkgo Bilobafor
Prevention of Dementia” is posted at<http://jama.ama-assn.org/cgi/content/abstract/300/19/2253>.
An abstract of “Risk-Reducing Effect of Education in Alzheimer's
Disease” is posted at<www3.interscience.wiley.com/journal/119179595/abstract>.▪