A herbal extract used as a treatment by people with dementia may not be as effective as thought, suggests a new study.
Ginkgo biloba is commonly marketed as an aid to memory and some studies have reported its benefits.
Researchers from Imperial College London studied 176 people with mild to moderate dementia. They were given 120 mg dose of ginkgo biloba daily.
They also studied participants' cognitive skills and quality of life at two, four and six months. The subjects were asked to take tests including exercises such as recalling words from memory or answering questions about time or places.
The researchers found no evidence proving that the standard dose of the herbal extract had any benefit on memory. Moreover, it also did not improve the quality of life.
A Cochrane review published in 2002, which had taken all relevant evidence into account, found ginkgo may be a small beneficial effect on memory in dementia patients.
Lead researcher Dr Rob McCarney said the lack of drug treatments in early dementia meant patients would try anything to slow down the progression of the disease.
"This isn't a hugely expensive treatment but if you're living on a state pension it can make a considerable dent in your budget," BBC quoted him as saying.
"The findings add to the growing evidence that ginkgo provides no benefit," he added.
Professor Clive Ballard, director of research at the Alzheimer's Society, said the finding was very disappointing.
"Thousands of people with dementia, who are already struggling to make ends meet, may buy ginkgo biloba expecting an improvement in their memory," Ballard said.
The results are in the International Journal of Geriatric Psychiatry.