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Effectiveness of Ginkgo Extract in Persons with No History of Neurocognitive Dysfunction
Effectiveness of Ginkgo Extract in Persons with No History of Neurocognitive Dysfunction

Reviewed: Mix J, Crews WD. A double-blind, placebo-controlled, randomized trial of Gingko biloba extract EGb 761® in a sample of cognitively intact older adults: neuropsychological findings. Human Psychopharmocology: Clinical and Experimental 2002;17:267-277.

In recent years, the use of ginkgo (Ginkgo biloba L., Ginkgoaceae) extract for the treatment of dementia and cerebral insufficiency has increased significantly. The results from a number of clinical trials have demonstrated the efficacy of ginkgo extract in cognitively impaired persons. In the last decade, ginkgo was approved as a treatment for dementia in Germany. The majority of studies have been conducted in Europe. Relatively few studies (approximately eight) have examined the effectiveness of ginkgo extract in persons with no history of neurocognitive dysfunction. The importance of such clinical research appears paramount in light of the number of products containing ginkgo with claims of enhanced cognitive performances that are currently being widely marketed to cognitively intact adults.

The purpose of this research was to conduct the first known, large-scale clinical trial to ascertain the efficacy of ginkgo extract (EGb 761, Dr. Willmar Schwabe GmbH & Co., Karlsruhe, Germany) on the neuropsychological functioning of cognitively-intact older adults. This study was intended to expand upon the authorsï' previous smaller study, which found that the extract had a positive effect on this particular group.1

In the current study, 262 male and female volunteers, 60 years of age and older, who reported no history of dementia or significant neurocognitive impairment were enrolled and randomized. The study utilized a 6-week, randomized, double-blind, fixed-dose, placebo-controlled, parallel-group experimental design. Individuals were randomly assigned to either the ginkgo extract (180 mg daily, 60 mg three times per day) or placebo for six weeks. Prior to the beginning of the study, participants were asked to complete an initial medical history questionnaire. Those with unremarkable medical or psychiatric history were administered the MMSE (Mini-Mental State Examination). Participants meeting the preliminary cognitive and medical inclusion criteria were subsequently administered a series of neuropsychological tests immediately prior to the initiation of ginkgo or placebo therapy, again after 6 weeks of treatment, and just prior to the termination of the study. Efficacy measures consisted of participantsï' raw changes in performance scores from pretreatment baseline to those obtained just prior to termination of treatment on the following standardized neuropsychological measures: Selective Reminding Test (SRT), Wechsler Adult Intelligence Scale-III Block Design (WAIS-III BD), Digit Symbol-Coding (WAIS-III DS) subtests, and the Wechsler Memory Scale-III Faces I (WMS-III FI) and Faces II (WMS-III FII) subtests. A subjective, follow-up, self-report questionnaire was also administered to participants just prior to termination of the treatment phase.

The analysis of the data revealed that participants who received 180 mg of ginkgo per day exhibited significantly more improvement on SRT tasks involving delayed (30 minutes) free recall (P < 0.04) and recognition of noncontextual, auditory-verbal material (P < 0.01), compared with the placebo controls. The ginkgo group also demonstrated significantly greater improvement on the WMS-III FII subtest assessing delayed recognition of visual material (human faces), compared with the placebo group (P < 0.025). However, there was a significant difference found between the two groupsï' pretreatment baseline scores on the WMS-III FII (P < 0.03), suggesting that this result should be interpreted with caution. Overall, the results from both objective, standardized, neuropsychological tests and a subjective, follow-up, self-report questionnaire provided complementary evidence of the potential efficacy of ginkgo extract in enhancing certain neuropsychological/memory processes of cognitively intact, older adults.

Only one serious adverse effect was reported during the current study and that was in the placebo group. All of the remaining adverse events reported were rated as either mild or mild to moderate in intensity and no causal relationship was determined with the ginkgo treatment. Overall, more adverse events were reported in the placebo group than the treatment group.

The results bolster the findings from the few previously published, small-scale studies that have found improvements in cognitive functioning among older cognitively intact adults and young, healthy volunteers. Although the precise mechanisms responsible for the current findings remain speculative, it seems plausible that several factors may have interacted additively to promote the enhancement of the ginkgo groups' memory processes.

-Densie Webb, Ph.D.


1. Mix J, Crews D. An examination of the efficacy of Ginkgo biloba extract EGb 761 on the neuropsychologic functioning of cognitively intact older adults. J Altern and Complement Med 2000;6:219-29.

2. Solomon PR, Adams F, Silver A, Zimmer J, DeVeaux R. Ginkgo for memory enhancement: a randomized controlled trial. JAMA 2002;288:835-40.

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