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ศุกร์, 02 มกราคม 2009

        The herbal product Ginkgo biloba is used frequently as a supplement intended to boost memory and prevent dementia, presumably through its antioxidant properties or anti-amyloid aggregation effects. Small trials have studied its efficacy in patients already with dementia, but to date no large study has evaluated the use of Ginkgo biloba for primary prevention of cognitive decline. The recent publication of a large randomized trial is a welcome addition to the literature.

        The authors performed a randomized, double-blind, placebo controlled trial of Ginkgo biloba for primary prevention of dementia in 3069 volunteers age 75 and older with either normal cognition (84%) or mild cognitive impairment (MCI, 16%). Those with dementia were excluded as were those taking warfarin, cholinesterase inhibitors, medications with psychotropic effects, and high-dose vitamin E. Participants were randomized in a 1:1 fashion to twice-daily doses of 120 mg Ginkgo biloba extract (EGb 761) or placebo; this formulation of Ginkgo biloba is used in many brands in the United States and has been previously studied. The primary outcome examined was the development of dementia using standard criteria along with detailed neuropsychologic testing and interviews.

A total of 1,524 patients were assigned to placebo and 1,545 patients were assigned to Ginkgo biloba with similar baseline characteristics. Mean age was 79.1 years and 54% were male. Participants were followed for a median of 6.1 years. A total of 523 patients were diagnosed with dementia during the course of the study including 246 (16.1%) in the placebo group and 277 (17.9%) in the Ginkgo biloba group; 92% of those with dementia were classified as Alzheimer's disease (AD). A total of 6.3% of the cohort, distributed evenly between the two groups, were either lost to follow up or withdrew from the study. The rate of development of all cause dementia did not significantly differ between the two groups (HR for Ginkgo biloba compared with placebo, 1.12; 95% CI, 0.94-1.33, p = .21) nor did the rates of development of AD (HR 1.16; 95%, CI 0.97-1.39, p = .11). Ginkgo biloba did not significantly affect the rate of progression to dementia in those patients with MCI at entry.

At the end of the trial, 60.3% of patients were still taking their assigned study medication, a rate that did not differ between the groups. There were no significant differences in the rates of serious adverse events between the two groups and no mortality difference was observed. Major bleeding did not significantly differ between the two groups, but patients taking anticoagulation were excluded from the study due to a known interaction between Ginkgo biloba and warfarin.

Taken as a whole, these results fail to demonstrate any effect of Ginkgo biloba on primary prevention of cognitive decline and argue against its use for this purpose. Furthermore, this is yet another trial that fails to demonstrate that a drug can influence the rate of progression of MCI to frank dementia. Clinicians should share this information with their patients currently taking or considering initiating Ginkgo biloba for the purpose of preventing cognitive decline.

 

References
Dekosky ST et al: Ginkgo biloba for prevention of dementia: A randomized controlled trial. JAMA 300:2253, 2008


S. Andrew Josephson, M.D., Department of Neurology, University of California San Francisco, San Francisco, USA

Last Updated ( ศุกร์, 02 มกราคม 2009 )
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