PEOPLE destined to suffer the misery of memory loss and senility could learn
their fate in advance, thanks to a new technique involving brain scanning. But
with no tried and tested cure yet available, would anyone really want to know?
There are also fears the results could be used by employers or insurance
companies to discriminate against people affected.
At the moment, most neurological diseases can鈥檛 be diagnosed until
behavioural problems start. But Mony de Leon of the New York University School
of Medicine and his colleagues have found that several years before the symptoms
of Alzheimer鈥檚 set in, part of the brain starts using less fuel.
The researchers studied 48 apparently healthy volunteers in their 60s, 70s
and 80s. At the start of the study all the volunteers achieved normal scores on
a number of cognitive tests, but when tested again three years later, 13 did
considerably worse. One was diagnosed with Alzheimer鈥檚 disease, while the
remaining 12 were diagnosed with 鈥渕ild cognitive impairment鈥� or MCI.
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All the volunteers had also been given a PET scan, which can show where
glucose is being metabolised in the brain. To find out if anything in the scans
could have predicted cognitive decline, the researchers selected 13 controls
matched for age, sex, education level and genetic risk of Alzheimer鈥檚 from the
people who were still healthy.
Leon鈥檚 team looked at several brain areas known to be involved in
memory鈥攁nd in Alzheimer鈥檚鈥攁nd found one important difference between
the group suffering memory loss and the controls. The entorhinal cortex used
substantially less glucose in those whose memory subsequently deteriorated. This
difference, the researchers say, can predict future memory loss up to three
years in advance. They report their findings in a future issue of Proceedings of
the National Academy of Sciences.
PET scans are too expensive and invasive for routine screening, so are only
useful for people already at high risk of Alzheimer鈥檚. But attempts to make the
approach more accessible are already under way. Cognitive computer scientist
Richard Granger of the University of California, Irvine, and his team have
developed a portable head cap which carries electrodes for analysing electrical
activity in the brain. The test takes only 12 minutes, and can pick out people
who already have Alzheimer鈥檚, MCI or depression with up to 98 per cent accuracy.
Granger is now using the test to look for patterns that are shared by the brains
of people who go on to suffer from particular diseases.
It remains to be seen whether the technique can predict these conditions
before clinical symptoms occur, and if so how early. 鈥淭hat鈥檚 exactly what we鈥檙e
trying to find out now,鈥� says Granger.
Gary Small, a neuroscientist at the University of California, Los Angeles,
believes that brain scans in some form could eventually be used routinely to
alert vulnerable people well in advance鈥攑erhaps decades ahead. Granger
believes that such early diagnosis can do only good. If people have a disease
then they will want to know about it as early as possible, he says.
鈥淭here are always risks for abuse,鈥� says Small, 鈥渂ut there are also
tremendous benefits.鈥� People who are told they will have Alzheimer鈥檚 could
decide whether to take preventive measures, he says. Antioxidants such as
vitamin E, anti-inflammatory drugs and cholinesterase inhibitors may all slow
the disease down, but it鈥檚 not clear by how much.