CONFUSION, anger, loneliness and despair. These are just some of the feelings people express when they discover they have Alzheimer鈥檚. But what if you knew twenty years beforehand that this was to be your fate?
That disturbing possibility has moved a step closer with a crucial advance in developing a blood test for Alzheimer鈥檚. The test spots the chemical markers for the disease decades before you鈥檇 develop symptoms. And the test itself may even double up as a potential treatment.
Alzheimer鈥檚 is the most common form of dementia in older people, striking about 3 per cent of men and women over 65, and roughly 50 per cent over 85. The disease鈥檚 hallmarks鈥攚hich can only be confirmed after death鈥攁re clumps of amyloid plaques and neurofibrillary tangles in the brain.
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Currently there are no effective treatments or cures. There have been numerous attempts to detect Alzheimer鈥檚 in advance but so far no reliable tests (快猫短视频, 9 August 2001, p 4). Most rely on brain scans, which are expensive and invasive. And even if they do bear fruit, they may only be able to predict the onset of the disease a few years in advance.
But David Holtzman at the Washington University School of Medicine in St Louis and his colleagues there and at pharmaceuticals company Eli Lilly, have discovered that an antibody, m266, seems to draw the amyloid out of the brains of mice and into the bloodstream.
They aren鈥檛 sure how it works, but they wondered if it could detect Alzheimer鈥檚 and even predict its severity. 鈥淥ne of the major things we鈥檙e looking for is a better biomarker for the disease,鈥� says Holtzman.
The researchers studied 49 middle-aged mice with a mutation that means they will develop an Alzheimer鈥檚-like disease. After measuring baseline blood levels of amyloid, they gave the mice the m266 antibody. At various intervals between 5 minutes and 24 hours later, they took fresh blood samples. After 24 hours, they autopsied the animals鈥� brains.
As in humans, the baseline levels of amyloid in the blood said nothing about the amount of amyloid in the brain. But samples taken a mere 5 minutes after the mice received the antibody correlated very closely with the amount of amyloid in two parts of the brain involved in Alzheimer鈥檚, the hippocampus and the cingulate cortex.
That might mean a version of m266 may have a similar effect in people. If so, a simple blood test could reveal who鈥檚 likely to develop the disease decades in advance. The characteristic amyloid plaques and tangles appear in the brain long before Alzheimer鈥檚 triggers changes in someone鈥檚 behaviour.
鈥淚t鈥檚 a solid finding,鈥� says Dale Schenk of Elan Pharmaceuticals in San Francisco, who has worked on a pioneering Alzheimer鈥檚 vaccine. 鈥淚 think it鈥檚 interesting, provocative.鈥� But he warns that it will be difficult to convert the test into a routine diagnostic procedure.
But if researchers can get the antibody to work in people, they hope it could also be used as a preventive treatment, sucking the amyloid out of the brain before it can cause dementia.