Alzheimer’s disease is a brain disorder that causes memory loss, confusion, personality changes, and a gradual loss of independence. It is the most common type of dementia. A person with this condition initially has little memory loss or confusion. This is called cognitive decline. But over time, these symptoms get worse. The disease progresses through three main stages of symptoms. In the final stage, Alzheimer’s patients are unable to talk to their families and are unable to know what is going on around them. The early signs of Alzheimer disease may not be obvious to anyone except the person with the disease and the people closest to them.