It is an irreversible progressive disorder wherein abstract thought and memory processes are impaired. The person may recall events happened in the past but unable to recall a just watched movie. Many people who are forgetful worry that their forgetfulness is a sign of Alzheimer's disease. Many of us forget where we put our keys one time or another but this is not an indication of Alzheimer's disease. An example of forgetfulness is when you cannot recall where you put your money but if you do not remember that money is use to buy things, that may be a sign of dementia.