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THURSDAY, Feb. 28 (HealthDay News) -- Ginkgo biloba, the popular herbal supplement widely promoted as a memory enhancer, offered no clear-cut protection against memory loss in octogenarians, a new study shows.
And a small but disturbing pattern showed up in those who took the herb extract during the three-year study, the researchers added.
"Seven had TIAs (transient ischemic attacks, or mini-strokes) or stroke," said study author Dr. Hiroko Dodge, an assistant professor of public health at Oregon State University. Exactly why this happened requires further study, she added.
Ginkgo biloba is believed to have antioxidant and anti-inflammatory properties, protecting cell membranes and helping govern the workings of the brain's chemical messengers, or neurotransmitters. Some studies have found that the herb may help some people with Alzheimer's disease.
Dodge's team evaluated 118 men and women aged 85 and older who were all free of memory complaints at the start of the study. They scored normally on a memory function test before being admitted to the study. Half were assigned to take 240 milligrams of ginkgo biloba extract daily; half got a placebo.
Overall, Dodge found that 21 people developed mild memory problems during the study—14 took placebo, and 7 took the ginkgo supplement. "There was a clear tendency that ginkgo prevents memory decline," but the differences in the preservation of memory between the two groups were not statistically significant, she said.
But when the researchers did a secondary analysis, taking into account the level of medication adherence, those who actually remembered to take the extract did show some benefit. "Those taking the ginkgo extract [on a regular basis] had a 70 percent lower risk of developing mild memory problems than those taking placebo," she said.
It is not clear whether the difference is a chance occurrence or not.
"We have to wait for larger studies," Dodge said.
More research is also needed, she said, on why the 7 participants who had strokes or mini-strokes were all on the extract and what that association might be.
Another expert agreed, calling the findings inconclusive.
"The study was really too small to provide conclusive results on the benefits and risks of ginkgo supplement," said Dr. Paul Aisen, director of the Alzheimer's Disease Cooperative Study at the University of California, San Diego.
"Without a larger study, I would certainly not recommend the use of ginkgo biloba extract in those 85 and over," he said. Overall, he added, the bulk of studies published in the medical literature do not provide enough proof to recommend the herb for preserving memory and cognitive function.
Likewise, the Alzheimer's Association says on its Web site that while the herb may help some people with Alzheimer's disease, further research is needed to find the exact way in which it works. Experts are awaiting the results of a much larger, multi-center trial based at the University of Pittsburgh. That trial compared the effects of the herb with a placebo in 3,000 people to see if ginkgo biloba helped prevent or delay the onset of Alzheimer's disease. The trial ran through 2007, and the results will not be available until some time later.
Dodge's study is published in the Feb. 27 online issue of Neurology.
SOURCES: Hiroko Dodge, Ph.D., assistant professor, public health, Oregon State University, Corvallis; Paul Aisen, M.D., director, Alzheimer's Disease Cooperative Study, and professor, neuroscience, University of California, San Diego; Feb. 27, 2008, Neurology online
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