When Alzheimer's disease actually starts is often not clear, but it now appears that it may be preceded by rapid cognitive decline for up to six years before it becomes evident, a new study suggests.
This accelerated deterioration in memory and other mental function is not seen in people who do not develop Alzheimer's disease, the researchers said.
"Alzheimer's disease has a much longer course and affects substantially more people than generally recognized," said lead researcher Robert S. Wilson, a senior neuropsychologist at the Rush Alzheimer's Disease Center in Chicago.