A timing diagram showing the seven stages of Alzheimer’s Disease. Alzheimer's disease is a type of dementia that causes problems with memory, thinking, and behavior. Eventually, the symptoms become severe enough to interfere with daily activities. To learn how you can support those afflicted by Alzheimer's disease, sign up for E-News. As for the Alzheimer Disease goes through seven stages from normal forgetfulness, early confusional, mild Alzhetmer's, moderately severe, and failure to thrive.