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Spinal Fluid Molecules May Predict Alzheimer's Disease

But some doctors wonder if test will work in ordinary medical practice

MONDAY, Feb. 6, 2006 (HealthDay News) -- Levels of certain molecules in cerebrospinal fluid might identify people in the early stages of Alzheimer's disease, Swedish neurologists report.

If the findings are verified in additional research, it may one day be possible to treat people early on, when there's still time to take corrective steps, the scientists said.

"The problem is that you start with patients with mild memory disturbances, and you don't know if it is just aging, depression or stress or Alzheimer's disease," said Dr. Kaj Blennow. He is a professor of clinical neurochemistry at Lund University, and a member of the team reporting the findings in the Feb. 6 online edition of Lancet Neurology.

The study of 180 people found that abnormal levels of molecules called b-amyloid, total tau and phosphorylated-tau in the fluid that bathes the brain and spinal cord predicted development of Alzheimer's disease with high accuracy over the next few years.

"You have to follow patients for a long time in such a study," Blennow said. "This study is the longest so far, with a follow-up of as much as six years."

In an average follow-up of four to five years, 42 percent of the people with what is formally known as mild cognitive impairment developed Alzheimer's disease, and 15 percent developed other forms of dementia. Combined measurements of total tau and beta-amyloid at the start of the study identified those who developed Alzheimer's with better than 90 percent accuracy, the researchers said.

Although no treatments have been shown to prevent dementia, "there are several studies underway with drug candidates with potential disease-modifying effects," Blennow said. "The main implication of our study is that if these drugs are effective, we could initiate treatment very early."

But, he added, more studies are needed because "while we have proof that they are good biomarkers, the question is how good they are. That will take a couple of years to determine." Several studies are ongoing in Sweden, Germany and the United States, he added.

But the value of these biomarkers may ultimately prove to be a moot question in the real world of medical practice, for several reasons, said Dr. John Morris, a professor of neurology at Washington University School of Medicine in St. Louis, whose group has done both biomarker and brain imaging studies for the prediction of dementia.

The imaging studies indicated that even in people with mild symptoms, substantial damage can be seen in important brain areas, Morris said, so attempts at early intervention might be fruitless.

"Even at the mild cognitive impairment stage, when we study the brains of individuals who have died of other causes, we see that their brains already have substantial losses in vulnerable brain regions," he said.

The Swedish study provides "valuable information," Morris added, but spinal taps to collect cerebrospinal fluid are not easily done in routine medical practice.

"We do cerebrospinal fluid studies also, but to make something useful for early detection in the real world, spinal taps are not the way to do it," he said. "We need even better markers or images than we have now. But that doesn't take away from what these researchers have done."

Those better markers could come from the Alzheimer's Disease Neuroimaging Initiative, now under way in the United States, said William Thies, vice president for medical and scientific affairs at the Alzheimer's Association. The study, which will have thousands of participants, is looking primarily at brain images but also has a biomarker component, he said.

The biomarkers identified in the Swedish study probably will have limited value in the United States because of the great difference between the health-care systems of the two countries, Thies said. Sweden has universal health insurance financed by the government, which paid for the study.

And use of spinal taps would be much more difficult in the United States because "nobody wants to pay for it and people are much more resistant to having a needle stuck in their back," he said. "What we need are biomarkers that are easily available."

More information

To learn more, visit the Alzheimer's Association.

SOURCES: Kaj Blennow, M.D., professor, clinical neurochemistry, Lund University, Lund, Sweden; John Morris, M.D., professor, neurology, Washington University School of Medicine, St. Louis; William Thies, Ph.D., vice president, medical and scientific affairs, Alzheimer's Association, Chicago; Feb. 6, 2006, Lancet Neurology online
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