Scans Track Alzheimer's-Linked Protein in Living Brains

WASHINGTON - Scientists have for the first time tracked the buildup of a protein implicated in Alzheimer's disease inside living human brains over two years, a step toward diagnosing the disease before memory fails and testing drugs that might slow it.

Using a PET scan and a dye that binds to amyloid — the sticky protein that forms the plaques long considered a hallmark of Alzheimer's — researchers followed patients and watched the protein accumulate even in some people whose minds were still sharp.

The finding, reported at a major Alzheimer's conference, supports the leading theory of the disease: that amyloid begins its damage years, perhaps decades, before symptoms appear.

It also sharpens the field's central dilemma. Several drugs that clear amyloid have failed to improve memory, raising the uncomfortable possibility that the plaques are a tombstone of the disease rather than its cause.

"If we treat only after memory fails, we are treating the end of a fire that started twenty years earlier," a researcher said. "These scans may finally let us see the smoke."

More than 5 million Americans have Alzheimer's, a toll projected to nearly triple by mid-century as the baby boom ages.

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Associated Press writers contributed to this report.

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