ST. LOUIS, Dec. 26 (UPI) -- Alzheimer's disease may begin in midlife, although the mind-killing condition is not diagnosed until a patient begins to show symptoms, U.S. researchers say.

"Alzheimer's disease may be a chronic condition in which change begins in midlife or even earlier," Dr. John C. Morris, director of the Alzheimer's Disease Research Center at Washington University in St. Louis told The New York Times. (NYSE:NYT)

Morris has been studying the possible progression of Alzheimer's in a healthy 52-year-old woman whose mother, grandmother and maternal great-aunt all had dementia to detect symptoms as early as possible.

The woman has volunteered for batteries of mental tests, MRIs, PET scans and spinal taps to help researchers who say early detection and treatment may be the only way to halt progression of Alzheimer's before brain damage spreads.

Since November, PET scans using an experimental radioactive dye called Pittsburgh Compound B have detected deposits of beta amyloid, an Alzheimer's-related protein, in the brains of five patients, the Times reported. Scientists say studies using the dye found A-beta deposits in up to 25 percent of normal people over age 65.

There currently is no definitive genetic test for biomarkers for Alzheimer's, which was first recognized in the early 1900s. The Alzheimer's Associated estimates 5 million U.S. residents have Alzheimer's and 66,000 die of the disease annually.