Mental faculties in Dementia not improved by homocysteine-lowering supplements
Jun 29, 2006 - 4:49:37 AM
Giving healthy older people supplements to reduce high blood levels of an amino acid linked to dementia does not help their cognitive performance, according to a major University of Otago clinical study published today in one of world's top medical journals.
In a two-year clinical trial involving more than 250 healthy older people, a multidisciplinary Otago research team investigated whether lowering their high blood levels of the amino acid, homocysteine, would positively influence their cognitive function, says study co-author Dr Jennifer McMahon, who conducted the trial as part of her PhD in Human Nutrition.
Previous international studies have shown an inverse relationship between homocysteine levels and cognitive function in older people, leading to hopes that lowering homocysteine might be the key to combating cognitive decline, says Associate Professor Murray Skeaff, another co-author.
"A high blood concentration of homocysteine is known as a significant risk factor for developing Alzheimer's, and is also linked to other forms of dementia and cardiovascular disease," says Assoc Prof Skeaff.
Over a two-year period, the Otago team of Human Nutrition, Psychology and Preventive & Social Medicine researchers tested whether lowering elevated levels of homocysteine in healthy over-65 year-olds through supplements would improve their performance in memory, thinking, language and learning tests.
The 253 trial participants (none of whom had been diagnosed with dementia but all of whom had high homocysteine levels) were divided into two groups. One group received a daily pill containing folate and vitamins B6 and B12, and the other group a placebo.
The researchers administered a battery of cognitive tests at the outset, one year in, and at the end of the two-year trial. While homocysteine levels fell sharply in the supplement group, the researchers found no significant overall difference between the groups' respective combined performances on a variety of cognitive tests, says Dr McMahon.
"Our study adds to the growing evidence pointing towards homocysteine as being merely a marker or a consequence of a number of health problems, rather than - as had previously been hoped - a key risk factor that could be tackled to prevent or treat them."
Doctors who are currently advising older patients to take supplements as a preventive measure against cognitive decline might need to reconsider that advice, she says.
The researchers wished to thank the Dunedin Community for the strong response when they called for volunteers to participate in the study.
Assoc Prof Skeaff added: "This incredible support from local people was vital in making this a high-powered trial that met the demanding standards of the New England Journal of Medicine.. Researchers from around the world continue to be amazed at the unique levels of participation Otago nutrition studies enjoy."
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