Memory impairment is a necessary feature for the diagnosis.
The rate of progression is different for each person. If AD develops rapidly, it is likely to continue to progress rapidly. If it has been slow to progress, it will likely continue on a slow course. The cause of Alzheimer's disease is not known, but it is NOT a part of normal aging. Prior theories regarding the accumulation of aluminum, lead, mercury, and other substances in the brain have been disproved.