Ginkgo biloba shows some potential against cognitive decline

Summarized by Susan Aldridge, PhD, medical journalist
March 10, 2008

Summary

A 3-year study among people over 85 has shown that ginkgo biloba has no obvious benefit in reducing the risk of cognitive decline, although the researchers say research on the supplement needs to continue.

Introduction

One of the biggest challenges we face, as an aging society, is how to prevent cognitive decline and dementia in the later years. Ginkgo biloba is a supplement which is widely used as a memory aid and there is some evidence that it may help cognitive performance in those who have dementia, or who are at risk of it. Ginkgo biloba is relatively cheap and has a good safety profile. It is thought to act as an antioxidant, thereby protecting the brain from biological aging. If it could be shown to be effective in warding off dementia, it would doubtless be widely used and of potentially massive benefit to the population. Researchers at Oregon State University now report on a clinical trial of gingko biloba in a group of individuals aged over 85, which happens to be the first study of dementia prevention in this age group.

What was done

The 118 participants in this study were the 'oldest old' - people age 85 or more, who are at high risk of developing dementia. At the start of the study, they had no memory problems and were not suffering from dementia. Half of them were given ginkgo biloba extract three times a day, while the other half took a placebo. The trial lasted for three years, during which time memory and cognitive performance were assessed regularly.

What was found

During the study, 21 participants developed mild dementia, of whom 14 were in the placebo group and seven in the gingko group. Progression to more severe dementia was noted in four of these people, three in the placebo group, one in the gingko group. Further analysis revealed that people who adhered most closely to the study regime, taking their supplement regularly, had the most to gain from gingko, with a 68 percent lower risk of developing mild memory problems.

When it came to safety, there was no overall different in mortality between the gingko and placebo groups. However, seven people on gingko suffered a stroke or transient ischemic attack . Gingko has been associated with possible bleeding problems, but most of these strokes were caused by blood clots rather than hemorrhage and they were mild.

What this study means

The researchers found a trend towards benefit from gingko in preventing memory loss and dementia, but their findings did not reach statistical significance. Therefore, from this study, we cannot be sure whether it is worthwhile taking gingko biloba supplements to ward off cognitive decline. Larger studies are now needed to see whether gingko really lives up to its age-old reputation as a tonic for the brain. Such studies are underway and it will be interesting to see what results are reported. They are the Gingko Evaluation of Memory study which is being carried out in the United States, and the European GuidAge study.

On safety, the increased occurrence of stroke among the gingko group sounds a cautionary note and requires further investigation. If you do take gingko biloba or any other supplement, always mention this to your doctor as it may interact unfavorably with prescribed medication.

Finally, the researchers noted the enthusiasm and commitment to the study of many of their participants. They note that the 'oldest old' should not automatically be excluded from clinical research on the assumption that they are too frail, too ill or unable to follow instructions. Many are pleased to have an opportunity to make their contribution to medical science. And, of course, they are an informative group when it comes to dementia research, because they are at such high risk of developing the condition. Dementia prevention research carried out in the over-85s may produce information which can benefit the whole population.

Source

• A randomized placebo-controlled trial of ginkgo biloba for the prevention of cognitive decline. Neurology online www.neurology.org HH. Dodge, T. Zitzelberger,  et al., -, February 27. 2008

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