New research seeks to delineate just how Alzheimer's disease unfolds in the human brain.
Biological changes may happen earlier than scientists had previously thought, according to a new disease model. This suggests that early signs of risk could potentially become treatment targets long before symptoms of Alzheimer's begin to appear, researchers said.
"We're getting a better idea of what is happening during the asymptomatic phases of the disease," said Dean Hartley, director of science initiatives at the Alzheimer's Association, who was not part of the new research.
The scientists behind the study identified distinct but overlapping phases in the course of the disease. Each was detectable by biological "markers" showing physical changes in the brain. They also have refined their model to distinguish between these "biomarkers" of Alzheimer's and those of normal aging.
In the first phase of Alzheimer's, brain markers signaling changes in beta-amyloid protein show up, the model suggests. Beta-amyloid plaques are protein pieces from the fatty membrane surrounding nerve cells that clump together, contributing to nerve dysfunction.
In the second phase of the disease, signs of degeneration and death of brain cells occur. Symptoms of dementia are seen in the third phase of Alzheimer's, according to the new model.
The refined model should help researchers design better methods of study, guide the selection of study participants, suggest the ideal time to begin treatment and help measure the impact of treatment, said Dr. Clifford Jack Jr. He is lead author of one of three related studies presented Tuesday in Boston at the Alzheimer's Association International Conference.