Alzheimer's Progression, Step by Step
As researchers learn more, therapy might someday address brain changes much sooner
Alzheimer's disease is an irreversible, progressive brain disease that slowly destroys memory and thinking skills. Symptoms typically appear after age 60, and about 5 million Americans may have the disease, according to the U.S. National Institute on Aging.
Jack and his team published a hypothetical model of the major Alzheimer's disease biomarkers in Neurology in 2010, describing how the biomarkers changed over time and were related to the beginning and progression of symptoms. For this study, the team reviewed studies that tested and evaluated that model, spurring them to further refine it.
How could the model spark new ideas for treating Alzheimer's disease? "What really makes sense probably is a combined therapeutic approach where you target a point or points in tau and in the amyloid pathways simultaneously," Jack explained.
Just as people often take statins -- drugs that lower cholesterol -- to reduce their risk of heart disease, it could someday be possible that those at risk for Alzheimer's could take medication to help prevent it, Jack said. He envisions a "cocktail" or combination of drugs that could target different points in the molecular pathways of the disease, administered at an early age, depending on a person's risk for Alzheimer's disease.
The Alzheimer's Association's Hartley said he's excited about the revised model. "It suggests that some of the treatments we're using may be too late in the progression of the disease."
Two related studies were also scheduled for presentation at the meeting. Dr. Victor Villemagne at the University of Melbourne, in Australia, and colleagues followed about 200 people with and without signs of Alzheimer's disease over four years to estimate when beta-amyloid levels tend to become abnormal. The scientists concluded that Alzheimer's disease is a slow process, likely extending for more than 20 years.
The other study, led by Daniela Bertens at VU University Medical Center, in Amsterdam, Holland, provided more evidence that abnormal beta-amyloid is what triggers the development of Alzheimer's disease. The research included about 300 people with abnormal beta-amyloid, and followed them over four years, testing their cerebrospinal fluid for diagnostic signs of the disease.
Because these studies were presented at a medical meeting, the data and conclusions should be viewed as preliminary until published in a peer-reviewed journal.