Research Points to Alzheimer's Blood Test

When effective drugs arrive, early detection will be key, experts say

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By Ed Edelson
HealthDay Reporter

THURSDAY, July 6, 2006 (HealthDay News) -- Researchers believe they've moved closer to a blood test for the early detection of Alzheimer's disease.

Increased blood levels of specific forms of beta amyloid proteins -- the abnormal molecules that are found in the brains of people with Alzheimer's disease -- were associated with an increased incidence of that condition and other forms of dementia, concludes a Dutch report published in the July 6 online edition of The Lancet Neurology.

"Beta amyloid comes in different lengths," explained Monique M. B. Breteler, a professor of neuroepidemiology at Erasmus Medical Center, in Rotterdam. "High blood levels of beta amyloid 1-40 and low levels of 1-42 were associated with an increased risk of Alzheimer's disease."

Those numbers refer to the number of amino acid components that make up the different versions of the protein.

In the study, Breteler's team tracked the mental health of 1,756 people, aged 55 years or older, for nearly nine years. Over that time, 392 participants developed some form of dementia.

The researchers found that participants with low blood levels of 1-42 and high levels of 1-40 at the start of the study had more than a tenfold higher risk of developing dementia than those with low levels of both proteins.

"This report is the first good indication that measuring blood levels of beta amyloids could be a step toward a potential test of risk," said Dr. John C. Morris, director of the Alzheimer's Disease Research Center at Washington University, in St. Louis.

It's only a small, preliminary step, he said. However, the Dutch finding is important because it indicates that something much simpler than a spinal tap might be useful in assessing the risk of dementia.

Beta amyloid 1-42 is believed to be the more dangerous form of the protein, Morris said. Tests of spinal fluid have shown lower levels of 1-42 than 1-40 in people with Alzheimer's disease, he said, presumably because more 1-42 is in the brain, forming plaques that then damage brain cells in several ways.

"Because blood is further away from the brain [than spinal fluid], we don't know if it reflects what is going on in the brain," Morris cautioned. However, the new study indicates that blood tests might give valuable information, he said.

According to Morris, "a scientist would emphasize that this is a step forward, but in no way assures us of a test." At best, Morris said, "this may be something that should be pursued."

Even if an early-detection test were to be developed, at the moment there's nothing doctors can do to slow or stop the progression of dementia, he pointed out. "There are some drugs for symptoms, but none yet have been determined to address disease progression," he said.

Still, there are a number of new drugs in the pipeline that might someday prove effective, he added. "Many of these potentially disease-modifying drugs are being evaluated in clinical trials," Morris said.

For that reason, the long-term goal is to devise a blood test that can spot dementia early, allowing doctors to treat it with drugs that slow or halt mental decline, Morris said.

More information

For more on dementia, head to the Alzheimer's Association.

SOURCES: Monique M. B. Breteler, M.D., professor, neuroepidemiology, Erasmus Medical Center, Rotterdam, Netherlands; John C. Morris, M.D., director, Alzheimer's Disease Research Center, Washington University, St. Louis; July 6, 2006, The Lancet Neurology

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