Ginkgo to Prevent Dementia? Forget About It

Jonathan Silver, MD


Journal Watch. 2008;7(11) 

In a GEM of a study, another alternative treatment bites the dust.


Several preclinical studies have suggested that Ginkgo biloba extract is neuroprotective, although some treatment studies (including meta-analyses) have shown little cognitive benefit. Americans are estimated to spend $100 million yearly on gingko in the hope that it enhances memory or prevents memory loss. To ascertain whether G. biloba prevents all-cause dementia and Alzheimer disease, researchers conducted the Ginkgo Enhancement of Memory (GEM) study, a multisite, randomized, controlled 6-year trial.

Researchers used an adequate sample size (calculated to detect a 30% reduction in dementia cases at 96% power). Individuals with mild cognitive impairment were included, but those with dementia were excluded, as were those treated with cholinesterase inhibitors, anticoagulants, and other potentially confounding treatments or conditions. The 3069 community volunteers (minimum age, 75) underwent a full baseline neuropsychological battery, were randomized to standardized G. biloba extract (120 mg twice daily) or placebo, and were reevaluated every 6 months. Participants with indications of cognitive decline retook the test battery; an expert panel reviewed results and clinical reports, finally referring patients for full neurologic evaluations and MRI scans for confirmation of dementia.

Dementia was diagnosed in 523 participants (placebo, 16.1%; ginkgo, 17.9%), with no between-group difference in baseline clinical characteristics or dropout rates. At study's end, 60.3% of participants were still taking the medication. Rates of all-cause or Alzheimer-type dementia did not differ between the two groups, although the number of hemorrhagic strokes was nonsignificantly higher in the gingko group.


This well-planned and well-executed study definitively answers the question of whether G. biloba prevents dementia: It does not, even in those with incipient dementia. The authors argue that because of dementia´s slow process, G. biloba given for a longer duration might be effective, and they plan further MRI analyses of some subjects. As an editorialist discusses, the investigators did not include data on overall cognitive decline or functional disability in this report. However, considering the lack of efficacy reported here, these measures are unlikely to yield positive findings. In the present economy, people can put the $100 million to better use.

— Jonathan Silver, MD

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