Alzheimer's Disease Biomarkers — Timing Is Everything

Alzheimer's disease typically evolves over a period of several years before an affected person seeks medical attention for a diagnosis. The pathologic features of the brain in patients with Alzheimer's disease include extracellular amyloid plaques, intraneuronal neurofibrillary tangles, and the loss of neurons and synapses. For decades, researchers speculated about which of these manifestations appears first. The discovery of rare genetic variants affecting the production of amyloid-beta (Aβ) peptide in autosomal dominant Alzheimer's disease provided the first clue. On the basis of this new information, researchers considered amyloid deposition to be the incipient process, followed by a cascade of other …