Ginkgo biloba ineffective against dementia: study
Published Tuesday, November 18, 2008 4:02PM EST
Ginkgo biloba, the herbal supplement that is sold in health-food stores as a memory enhancer, does not prevent the onset of dementia or Alzheimer's disease, new research suggests.
In a study of 3,000 elderly patients, American researchers found that rates of dementia or Alzheimer's disease were similar among patients who took Ginkgo and those who took a placebo.
The findings showed:
- 3.3 dementia cases per 100 persons per year in the Ginkgo biloba group compared to 2.9 cases among the placebo group.
- 3.0 Alzheimer's cases per 100 persons per year in the Ginkgo biloba group compared to 2.6 among the placebo group.
The natural supplement also did not have an effect on the rate of progression to full-blown dementia in patients who already showed signs of mild cognitive impairment.
The results indicate that Ginkgo biloba should not be recommended for the prevention of dementia, the authors wrote.
"It is very unlikely that Ginkgo biloba is effective at any dose over a five-year period and in anyone over 75 years old," Dr. Jeff Williamson, principal investigator at the study's Wake Forest University Baptist Medical Center research site, said in a statement.
"It is also ineffective in people with signs of early memory loss. What is not known yet is whether the effect of Ginkgo biloba might require taking the drug for many, many years, say 15 years, before there is even a sign of memory loss."
The findings are published in the Journal of the American Medical Association.
Alzheimer's disease affects about 300,000 Canadians over the age of 65, according to the Alzheimer's Society of Canada. It is the most common form of dementia, has no cure, and is a progressive, degenerative disease that destroys brain cells.
It is a major cause of age-related hospitalization and placement in long-term care facilities, according to supplementary information included with the study.
While there are currently no medications that are approved for the prevention of dementia, Ginkgo biloba is used in many parts of the world in hopes of preserving memory function and improving a variety of health conditions, from MS symptoms to sexual dysfunction.
However, few studies have evaluated its safety and effectiveness for the prevention of dementia.
For this research, patients were 75 years of age or older and had either normal cognitive function or mild cognitive impairment.
The subjects took either a twice-daily dose of 120 mg of Ginkgo biloba or a placebo and were followed for an average of 6.1 years.
During that period, 17.9 per cent of patients in the Ginkgo group were diagnosed with dementia, compared to 16 per cent of patients in the placebo group.
The findings not only question the use of Ginkgo biloba for the prevention of dementia, the researchers said. They also indicate the importance of clinical trials for assessing the benefits of alternative therapies.