reviewed by X. Li, Ph. D.
(credential)
So far the largest and most thorough clinical trial for treatment of ginkgo biloba in dementia1 was
conducted in USA and published in JAMA, the Journal of the American Medical Association, a highly regarded
and peer-reviewed medical journal. This is a 52-week randomized, placebo-controlled, double-blind trial conducted in 6 medical
centers including New York Institute for Medical Research, Harvard Medical Center, and UCLA Medical center.
In this trial, 327 patients who had either the Alzheimer type dementia (251 patients) or multi-infarct
dementia were enrolled. These patients were lack of other significant medical conditions. They are 45 to 90
years old and of both sexes. They all have mild to moderately severe dementia as assessed by a special
test called Mini-Mental State Examination. The patients were randomly divided into two equally sized groups.
One group took a 40 mg tablet of the standardized ginkgo biloba extract orally three times daily before
meals. The other group took the placebo tablet in same way. The placebo tablet matched the ginkgo tablet
in appearance and smell/taste. The whole procedure was managed by an independent third party. Whether a patient took
ginkgo or placebo was sealed for both the patient and the researchers until the end of measure collection.
Researchers then took three measures to assess the change in mental performance of patients. The first is
the Alzheimer's Disease Assessment Scale (ADAS-Cog), which objectively evaluates memory, language, praxis,
and orientation. The second is the Geriatric Evaluation by Relative's Rating Instrument (GERRI), which is completed
by the caregiver to evaluate the patient's daily living and social behavior. The third is the Clinical Global
Impression of Change (CGIC), which quantifies the physician's judgment of any change in overall impairment
of the patient since the start of study. The measures were taken at week 12, 26, and 52.
The measures from both groups were then subject to statistical analysis to determine if any measure is different
between patients who took ginkgo and patients who took dummy and between the end and the start of the study.
Below is what they found.
(1) The ADAS-Cog score, a standard and objective measure of cognitive impairment, remains the same in the ginkgo group of patients.
after 52 week trial. However, the score is worsened by 1.5 points in the placebo group of patients.
This difference is statistically very significant (P=0.006). Because dementia typically gets worse over
time, just as seen in the placebo group of this study, a stable ADAS-Cog in the ginkgo group indicates that dementia has been
stabilized by the ginkgo treatment.
(2) The GERRI score, an evaluation of daily activity by caregivers, showed a mild improvement in the ginkgo group.
However, the score is significantly worsened in the placebo group, resulting in a significant difference
in favor of the ginkgo-treated group (P=0.004). As GERRI was found to highly correlate with the overall
symptom severity of dementia, its improvement rather than worsening in the ginkgo group again suggests
that ginkgo stabilized and even improved the dementia.
(3) The CGIC score, a global psychopathology evaluation by physicians, showed slight worsening in
both groups and no difference was found between the groups. This is in contrast to the findings above and
may be related to the low sensibility and reliability of the measure method itself. For example, it
asks the physician's impression on the change in patients compared to the start of the study. As the study
interval increases the physician's memory gets less reliable.
(4) When counting how many patients showed the improvement in the ADAS-Cog in each group,
it was found that 29% patients in the ginkgo group showed at least 4 points of improvement whereas only
13% patients in the placebo group showed the same effect. Because clinically 4 ADAS-Cog point improvement
is considered to be equivalent to a 6-month delay in the progression of the dementia, this result
indicates that 16% patients treated with ginkgo actually achieved the clinically
manifested improvement due to the standard ginkgo extract.
(5) The difference between the ginkgo and placebo groups was observed from the measures at week 12 and
gets more and more pronounced at week 26 and 52. This suggests the sustained benefits of taking ginkgo
for a long duration.
(6) The study further compared the effect of ginkgo on mild or modestly severe dementia2.
It was found that to mild cognitive impairment ginkgo made 1.7 points improvement. To more severe
dementia, ginkgo effect is more on the stabilization of the disease.
In this reviewer's summary, the above trial represents so far the most carefully designed and conducted
study on the treatment value of the ginkgo extract on dementia. The trial outcome strongly suggests that
the standardized ginkgo biloba extract can stabilize and, in a substantial number of cases, improve the
cognition and mental performance of dementia patients.
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Reference
1. Le Bars PL, Katz MM, Berman N, Itil TM, Freedman AM, Schatzberg AF. A placebo-controlled, double-blind, randomized trial of an extract of Ginkgo
biloba for dementia. North American EGb Study Group. JAMA. 1997
Oct 22-29;278(16):1327-32.
2. Le Bars PL, Velasco FM, Ferguson JM, Dessain EC, Kieser M, Hoerr R. Influence of the severity of cognitive impairment on the effect of the Gnkgo
biloba extract EGb 761 in Alzheimer's disease. Neuropsychobiology. 2002;45(1):19-26.
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