The onset of Alzheimer's disease is usually gradual, and it is slowly progressive. Memory problems that family members initially dismiss as "a normal part of aging" are in retrospect noted by the family to be the first stages of Alzheimer's disease. When memory and other problems with thinking start to consistently affect the usual level of functioning; families begin to suspect that something more than "normal aging" is going on.
Problems of memory, particularly for recent events (short-term memory) are common early in the course of Alzheimer's disease. For example, the individual may, on repeated occasions, forget to turn off an iron or fail to recall which of the morning's medicines were taken. Mild personality changes, such as less spontaneity, apathy, and a tendency to withdraw from social interactions, may occur early in the illness.
As the disease progresses, problems in abstract thinking and in other intellectual functions develop. The person may begin to have trouble with figures when working on bills, with understanding what is being read, or with organizing the day's work. Further disturbances in behavior and appearance may also be seen at this point, such as agitation, irritability, quarrelsomeness, and a diminishing ability to dress appropriately.