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New definition of Alzheimer’s proposed by researchers

Biological changes in the brain show up years before such symptoms as memory loss, an international team of scientists said. Patients diagnosed because of the change may be eligible for treatments under study.

Brain scans and other testing would help identify

Brain scans and other testing would help identify Alzheimer's patients earlier in the course of the disease, researchers say. Photo Credit: AP / Evan Vucci

An international team of scientists, led by researchers in the United States, is proposing a new way of defining Alzheimer’s disease, basing it on biological changes in the brain — and not waiting for symptoms such as memory loss to emerge.

The proposal, published Tuesday in a major medical journal, is aimed at improving research into treatments by emphasizing a “biological construct” of the disease.

Changes in the brain show up years — and sometimes decades — before overt symptoms appear, scientists said. By redefining Alzheimer’s based on biological markers, patients could be more appropriately matched for treatments under study that might slow or reverse the disease, according to the proposed redefinition.

“We have always supported early diagnosis, particularly if there is a family history of Alzheimer’s disease,” said Mary Ann Malack-Ragona, executive director of the Alzheimer’s Disease Resource Center in Bay Shore, who was not part of the research. She applauded the proposed move away from a symptom-based definition.

About 5.7 million people nationwide have Alzheimer’s disease based on its current definition. However, an estimated 50 million people worldwide are afflicted with some form of dementia, the most common of which is Alzheimer’s disease, according to statistics from the National Institute on Aging.

Currently, the definition of Alzheimer’s is based on patients’ behavior in addition to results of tests that measure a number of cognitive parameters and memory, said Dr. Nina Silverberg, director of Alzheimer’s disease programs at the institute.

“There is still so much that we don’t know about Alzheimer’s and how it plays out in different people,” added Silverberg, who wrote a commentary that accompanied the massive new proposal.

Both documents were published Tuesday in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.

Silverberg said there hadn’t been a new Alzheimer’s drug in a decade. A keener definition will help target patients for medication trials that best fit the biology of their disease. She said doctors would not have to change what they are currently doing. The proposal is largely aimed at Alzheimer’s researchers at this juncture.

A combination of brain scans and other methods of diagnosis, such as blood tests that spot specific Alzheimer’s markers, would help identify people earlier in the course of the disease.

In addition, redefining the condition objectively would mean that the numbers of people diagnosed may increase dramatically, experts said.

“We have to focus on biological or physical targets to zero in on potential treatments for Alzheimer’s,” Dr. Eliezer Masliah, director of the neuroscience division at the National Institute on Aging, said in a statement.

“By shifting the discussion to neuropathologic changes detected in biomarkers to define Alzheimer’s, as we look at symptoms and the range of influences on development of Alzheimer’s, I think we have a better shot at finding therapies, and sooner,” Masliah said.

Basing a diagnosis on biological markers rather than symptoms guards against misdiagnosis, because other conditions can masquerade as Alzheimer’s disease, Malack-Ragona said.

A patient at her center once was thought to have Alzheimer’s disease based on symptoms, but later was found to have a brain tumor. Extreme dehydration, which can occur among elderly people or through thyroid conditions, also can produce problems with memory and be mistaken as Alzheimer’s disease, she said.

Authors of the new research include scientists from the National Institute on Aging, a division of the National Institutes of Health, and the Alzheimer’s Association, as well as from major research centers in this country and abroad. The collaborative scientific effort represents years of scientific research, team members wrote.

“The reason we support this kind of position is that a family has to make very special plans when they suspect that someone is predisposed to Alzheimer’s or other dementias,” Malack-Ragona said.

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