By Merritt McKinney
NEW YORK, Aug 16 (Reuters Health) - Older people who have a normal memory
but are genetically at risk of Alzheimer's disease have to kick their brains
into overdrive to perform the same memory tasks as others who are not at risk of
the disease, according to results of a new study.
The test used to measure brain activity in the study may help identify
people at risk of Alzheimer's, the study's lead author told Reuters Health in an
interview.
"People with a genetic risk for Alzheimer's have to use their brains more to
perform memory tasks than people who don't have that genetic risk," said Dr.
Gary W. Small, of the University of California, Los Angeles. He explained that
the activity was greatest in areas of the brain that are eventually affected by
Alzheimer's disease.
And the brain scan was a good predictor of a person's memory a couple of
years later, when some of the participants were retested, according to Small.
"We saw that the people who had greater brain activation during a memory task
were the ones that had worse memory performance 2 years later," he said.
Small and his colleagues based the findings on 30 people aged 47 to 82 who
did not have any memory problems, including 16 who had a genetic variation known
as APOE-e4, which is linked to an increased risk of Alzheimer's disease. There
are three different APOE genes--e2, e3 and e4--people with one or two copies of
APOE-e4 (from one or both parents) are at greater risk than those with a
different combination of the genes.
In the study, all participants underwent a brain scan called functional
magnetic resonance imaging while performing a series of memory tests. The
results of the study are published in the August 17th issue of The New England
Journal of Medicine.
It may seem odd that increased brain activity may signal a risk for memory
loss, but Small said that the phenomenon makes sense. He likened the bran scan
to a cardiac stress test, during which a person's heart is monitored during
exercise. Just as the heart of a person with heart disease has to work harder
than that of an athlete during exercise, the brain of a person at risk of
Alzheimer's appears to have to work harder to perform the same task as someone
who is not at risk, according to Small.
The researcher explained that not everyone with a genetic risk factor for
Alzheimer's will develop the disease, since it is caused by a combination of
genetic and environmental factors. However, measurements of brain activity,
along with other tests, may help identify people at risk of developing the
disease, Small and his colleagues note.
The findings may help identify good candidates for clinical trials of drugs
designed to slow down or stop the progression of Alzheimer's disease, Dr. Ingmar
Skoog, of Sahlgrenska University Hospital in Sweden, writes in an accompanying
editorial. The test may also be used to see how well such drugs work, Skoog
notes.
