A new study has failed to find any benefit of Ginko biloba extracts in the treatment of dementia and age-related memory impairment. These results have come as some surprise, because Ginko has in the past gained some credibility among practitioners of conventional medicine.

In a study of 214 elderly patients with memory impairment, split into three groups and given either one of two different doses of Ginkgo biloba extract EGb 761 or a placebo, no differences were detected in memory function after 24 weeks (J Am Geriatr Soc 2000; 48: 1­12). This result has caused some confusion, for in the past a number of controlled clinical trials of the extract have shown a small but significant beneficial effect on memory function in patients (Lancet 1992; 340: 1136­39). In Germany, France, and more recently in the USA, standardised extracts of Ginkgo leaves are popular in the treatment of peripheral vascular disease, memory impairment, depression, and anxiety. In Germany, Ginkgo is one of the most commonly prescribed drugs with an estimated market in 1989 of E150 million.

So why did the new study fail to detect any such effects? "One of the main differences between previous studies and ours, is the effort we took to find a suitable placebo", says lead investigator Martien van Dongen (University Maastricht, Netherlands). "Ginkgo has a very pronounced taste and smell, so it took some time to develop a good placebo", he explains. "The fact that we now failed to detect any effect whatsoever on a large number of tests, provides serious doubts as to its benefits on memory function". Philip Scheltens (Free University Amsterdam, Netherlands), however, questions the external validity of the study, saying "This study included all kinds of memory loss, so I am not surprised it didn't find any effect in such a heterogeneous population".

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