The placebo-controlled, double-blind study investigated the effects of a standardized ginkgo extract in 309 patients with mild-to-severe dementia associated with either Alzheimer's disease or multi-infarct dementia. Patients were randomized to receive 52 weeks of treatment with placebo or ginkgo extract at a dose of 40 mg three times a day, a total daily dose of 120 mg. At 52 weeks, 202 patients were included in the endpoint analysis, which was based on standard tests of cognitive impairment, daily living and social behavior, and general psychopathology.
The researchers reported that 27 percent of patients who provided data for the 52-week analysis experienced at least a four-point improvement on the 70-point Alzheimer's Disease Assessment Scale-Cognitive subscale (ADAS-Cog), compared to 14 percent in the placebo group. Daily living and social behavior were deemed improved in 37 percent of ginkgo patients, compared to 23 percent of those taking placebo, as measured by the Geriatric Evaluation by Relative's Rating Instrument (GERRI). In contrast, the GERRI showed that 40 percent of patients taking placebo experienced a worsening of their condition, while worsening was seen in only 19 percent of those taking ginkgo.
The authors concluded that "EGb appears to stabilize and, in an additional 20 percent of cases (vs. placebo), improve the patient's functioning for periods of six months to one year. Regarding its safety, adverse events associated with EGb were no different from those associated with placebo."
The ginkgo preparation used in the study (EGb 761) is a concentrated leaf extract standardized to 24 percent ginkgo flavonol glycosides and 6 percent terpene lactones, the same extract widely used in Europe for the treatment of cognitive and circulatory disorders and other conditions. This extract, manufactured by Dr. Willmar Schwabe AG in Karlsruhe, Germany, is currently available in the United States under the trade names Ginkgold(R) (from Nature's Way Products, Inc.) and Ginkoba(TM) (from Pharmaton Natural Health Products).
The results of the JAMA study are in agreement with other investigations on the efficacy of ginkgo in senile dementia and Alzheimer's disease. Similar results with ginkgo in Alzheimer's were recently reported in the journal Phytomedicine. (Kanowski et al., 1997. See "Effectiveness of Ginkgo biloba extract in Alzheimer's and multi-infarct dementia," HerbalGram 41,17).
[Kanowski S., W.M. Herrmann, K. Stephan, W. Wierich, R. Horr. 1997. Proof of efficacy of the Ginkgo biloba special extract EGb 761 in outpatients suffering from mild to moderate primary degenerative dementia of the Alzheimer's type or multi-infarct dementia. Phytomedicine, Vol. 4, No.1:3-13.
LeBars EL., M.M. Katz, N. Berman, M. Turan, A.M. Freedman, A.F. Schatzberg. 1997. A placebo-controlled, double-blind, randomized trial of an extract of Ginkgo biloba for dementia. JAMA, Vol. 278:1327-1332.]
Article copyright American Botanical Council.