Ginkgo biloba for Memory Loss In the Elderly(February 19, 2008) By Donald Brown, ND

A new clinical trial suggests that the popular herbal supplement Ginkgo biloba extract (GBE) may be no more effective than a placebo in treating memory loss associated with aging or Alzheimer?s disease.

Published in the Journal of the American Geriatrics Society, the trial recruited 214 elderly people from nursing homes throughout the Netherlands.1 Of these people, 151 were diagnosed with age-associated memory impairment (AAMI) and 63 with dementia?either Alzheimer?s disease or vascular dementia. Participants were assigned to one of five groups: (1) treatment with 240 mg/day of GBE for 24 weeks; (2) treatment with 240 mg/day of GBE for 12 weeks followed by 12 weeks of placebo; (3) treatment with 160 mg/day of GBE for 24 weeks; (4) treatment with 160 mg/day of GBE for 12 weeks followed by 12 weeks of placebo; or (5) placebo for 24 weeks.

Participants were evaluated at 12 and 24 weeks using a battery of tests to determine mental performance and questionnaires to determine daily living skills and mood. While use of ginkgo at both dosages was found to mildly improve daily living skills and the ability to perform a task that required placing 30 numbers in order as quickly as possible, the investigators report that GBE was no better than placebo in its effect on mental performance, including memory. The investigators write, ?We conclude that our trial has failed to reproduce the beneficial effects of ginkgo in older patients with dementia and age-associated memory impairment that have been demonstrated by many previous trials.

This is the first major U.S. publication on GBE for dementia since the 1997 study published in the prestigious Journal of the American Medical Association (JAMA).2 The results are clouded by several problems with the study design. The study attempts to evaluate two very different types of patients?those with dementia and those with AAMI. AAMI is a benign form of memory loss in the elderly that is not due to dementia. While the diagnosis of AAMI may have been considered acceptable when this trial was being conducted in the early to mid-1990s, the diagnosis of AAMI has since been roundly criticized as vague and difficult to validate. The results of the study are weakened by the fact that the investigators chose to combine results from both AAMI and dementia patients instead of considering these distinctly different patients separately. Previous trials with GBE have not studied people with AAMI, opting instead to study people with mild cognitive impairment (sometimes called age-related cognitive impairment)?a condition that sometimes precedes dementia.3 4 These trials found that GBE successfully improved mental performance.

The form of GBE used in this study, EGb 761, has been shown in two well-designed studies to effectively treat people with mild to moderate dementia when used for 6 to 12 months.5 6 In a 1997 editorial, JAMA senior editor Margaret Winkler, MD, stated, ? . . . this agent (EGb 761) is an intriguing addition to the drugs thought to be helpful for pateints with Alzheimer?s disease.?7 The current trial is designed differently from the design used in previous trials that all found GBE to have a therapeutic effect, and it suffers from attempting to analyze too few patients divided among too many treatment regimens.

The lead investigator of the study, Dr. Martien van Dongen, acknowledges the disparity between his findings and the outcomes reported by almost all other researchers. One distinct difference between the participants in this study vs. those in previous studies is the choice of nursing home residents as opposed to patients still residing at home. Dr. van Dongen suggests that the older age of the patients in his study (average was 82.6 years) may have affected the results negatively. He concludes the paper by stating, ?At this time, we cannot fully rule out the possibility that our negative trial was an outlier by chance.? (An outlier is a study that produces results far different from that of other studies, often for unknown reasons. Scientists consider the findings of outliers with suspicion.)

GBE continues to be one of the most promising treatments for mild to moderate dementia as well as mild cognitive impairment. The herbal extract has recently captured the interest of the National Institutes of Health, which granted the University of Pittsburgh School of Medicine a $15 million award for a major multicenter study to test the effectiveness of GBE in the prevention of dementia in the elderly. The six-year study plans to enroll 3,000 participants.

Source:

1. van Dongen M, van Rossum E, Kessels AGH, et al. The efficacy of ginkgo for elderly people with dementia and age-associated memory impairment: New results of a randomized clinical trial. J Am Geriatr Soc 2000;48:1183?94.
2. Le Bars PL, Katz MM, Berman N, et al. A placebo-controlled, double-blind, randomized trial of an extract of Ginkgo biloba for dementia. JAMA 1997;278:1327?32.
3. Wesnes K, Simmons D, Rook M. A double-blind, placebo-controlled trial of Tankakan in the treatment of idiopathic impairment in the elderly. Human Psychopharmacol 1987;2:159?69.
4. Israel L, Dell?Accio E, Martin G, Hugonot R. Ginkgo biloba extract and memory training programs?comparative assessment on elderly outpatients. Psychologie Medicale 1987;19:1431?9.
5. Kanowski S, Herrmann W, Stephan K, et al. Proof of efficacy of the Ginkgo biloba special extract EGb 761 in outpatients suffering from mild to moderate primary degenerative dementia of the Alzheimer type or multi-infarct dementia. Pharmacopsychiatry 1996;29:47?56.
6. Le Bars PL, Katz MM, Berman N, et al. A placebo-controlled, double-blind, randomized trial of an extract of Ginkgo biloba for dementia. JAMA 1997;278:1327?32.
7. Winkler MA. Aging: A global issue [editorial]. JAMA 1997; 278:1378.

Donald Brown, ND, is a naturopathic physician and one of the leading authorities in the United States on evidence-based herbal medicine. He is the founder and director of Natural Product Research Consultants, Inc., and serves on the Advisory Board of the American Botanical Council and the President?s Advisory Board of Bastyr University.