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WASHINGTON (Reuters) - A gene known to raise the risk of Alzheimer's disease may alter brain activity throughout life, British researchers said on Monday.
They found that young adults with the so-called APOE4 gene type had distinct brain patterns and said their finding might lead to a better test for Alzheimer's risk.
Even when they were not doing anything, people with the APOE4 gene had busier brains than people with other forms of the APOE gene, the researchers reported in the Proceedings of the National Academy of Sciences.
When they did a memory task, the APOE4 carriers had more activity in a part of the brain called the hippocampus, which is involved in long-term memory and navigation and which is the first area known to be affected in Alzheimer's disease.
It could be that the brain just wears itself out in some people, said Dr. Christian Beckmann of Imperial College London, who worked on the study.
"We were surprised to see that even when the volunteers carrying APOE4 weren't being asked to do anything, you could see the memory part of the brain working harder than it was in the other volunteers," Beckmann said in a statement.
"Not all APOE4 carriers go on to develop Alzheimer's, but it would make sense if in some people, the memory part of the brain effectively becomes exhausted from overwork and this contributes to the disease."
The APOE4 gene variant is found in about a quarter of the population. Not everyone who has it develops Alzheimer's but those who have one copy have four times the normal risk and people with two copies have 10 times the risk.
"These are exciting first steps toward a tantalizing prospect: a simple test that will be able to distinguish who will go on to develop Alzheimer's," Dr. Clare Mackay of the University of Oxford, who led the study, said in a statement.
The researchers used a type of real-time imaging called functional magnetic resonance imaging or fMRI to look at the brains of 36 volunteers aged 20 to 35, 18 who had at least one copy of APOE4.
None of the volunteers had any memory problems and the researchers stressed the findings did not mean they were fated to develop Alzheimer's.
"We have shown that brain activity is different in people with this version of the gene decades before any memory problems might develop," Mackay said.
"We've also shown that this form of fMRI, where people just lie in the scanner doing nothing, is sensitive enough to pick up these changes."
Dr. Peter Nestor of the University of Cambridge, a neuroscientist who was not involved in the study, said more research is clearly needed.
"The findings of this study are of considerable interest but should not be over-interpreted to mean that Alzheimer's disease is already starting to develop in this young, healthy group of volunteers," Nestor said in a statement.
Reporting by Maggie Fox