THE EFFICACY OF GINKGO-BILOBA ON COGNITIVE FUNCTION IN ALZHEIMER-DISEASE

Objective: To determine the effect of treatment with Ginkgo biloba ext ract on objective measures of cognitive function in patients with Alzh eimer disease (AD) based on formal review of the current literature. M ethods: An attempt was made to identify all English and non-English-la nguage articles in which G biloba extract was given to subjects with d ementia or cognitive impairment. Inclusion criteria for the meta-analy sis were (1) sufficiently characterized patients such that it was clea rly stated there was a diagnosis of AD by either Diagnostic and Statis tical Manual of Mental Disorders, Revised Third Edition, or National I nstitute of Neurological Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria, or there was enough clinical d etail to determine this by our review; (2) clearly stated study exclus ion criteria, ie, those studies that did not have stated exclusions fo r depression, other neurologic disease, and central nervous system-act ive medications were excluded; (3) use of standardized ginkgo extract in any stated dose; (4) randomized, placebo-controlled and double-blin d study design; (5) at least 1 outcome measure was an objective assess ment of cognitive function; and (6) sufficient statistical information to allow for meta-analysis. Results: Of more than 50 articles identif ied, the overwhelming majority did not meet inclusion criteria, primar ily because of lack of clear diagnoses of dementia and AD. Only 4 stud ies met all inclusion criteria. In total there were 212 subjects in ea ch of the placebo and ginkgo treatment groups. Overall there was a sig nificant effect size of 0.40 (P<.0001). This modest effect size transl ated into a 3% difference in the Alzheimer Disease Assessment Scale-co gnitive subtest. Conclusions: Based on a quantitative analysis of the literature there is a small but significant effect of 3- to 6-month tr eatment with 120 to 240 mg of G biloba extract an objective measures o f cognitive function in ED. The drug has not had significant adverse e ffects in formal clinical trials but there are 2 case reports of bleed ing complications. In AD, there are limited and inconsistent data that preclude determining if there are effects on noncognitive behavioral and functional measures as well as on clinician's global rating scales . Further research in the area will need to determine if there are fun ctional improvements and to determine the best dosage. Additional rese arch will be needed to define which ingredients in the ginkgo extract are producing its effect in individuals with AD.