Dementia, especially Alzheimer's disease, is a leading cause of age-related disability and long-term care placement in the United States. Although the herbal supplement Ginkgo biloba is widely used for its purported effects on memory and cognition, clinical evidence of its effect on the incidence of dementia is lacking. Researchers analyzed data from the Ginkgo Evaluation of Memory (GEM) study to determine whether ginkgo reduces the incidence of overall dementia and Alzheimer's. The GEM research was cofunded by NCCAM and four other components of the National Institutes of Health.
The GEM study—the largest of its kind to date—was a randomized, double-blind, placebo-controlled clinical trial of 3,069 community-dwelling older adults (mean age 79.1 years), conducted in multiple academic medical centers in the United States between 2000 and 2008. The median followup time was 6.1 years. Participants, who had normal cognition or mild cognitive impairment when they entered the study, received 120 mg of ginkgo or an identical-appearing placebo twice daily and underwent assessments for dementia every 6 months over the course of the study.
Ginkgo was not effective in reducing the incidence of overall dementia or Alzheimer's dementia. During the study, 523 participants developed dementia (246 receiving placebo and 277 receiving ginkgo), with 92 percent of the dementia cases classified as Alzheimer's.
The researchers pointed out that the dropout rate in the GEM study was similar to, or better than, dropout rates in studies of younger populations—a rationale for including older individuals in future randomized trials of promising interventions for preventing or delaying dementia.
DeKosky ST, Williamson JD, Fitzpatrick AL, et al. Ginkgo biloba for prevention of dementia. Journal of the American Medical Association.; 300(19):2253–2262.2008