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Alzheimer’s disease is the most common cause of mental decline, or dementia. But dementia also has many other causes. For more information, see the topic Dementia.

What is Alzheimer's disease?

Alzheimer's disease damages the brain . It causes a steady loss of memory and of how well you can speak, think, and carry on daily activities.

Alzheimer's disease always gets worse over time, but how quickly this happens varies. Some people lose the ability to do daily activities early on. Others may still do fairly well until much later in the disease.

Mild memory loss is common in people older than 60. It may not mean that you have Alzheimer’s disease. But if your memory is getting worse, see your doctor. If it is Alzheimer’s, treatment may help.

What causes Alzheimer's disease?

Alzheimer’s disease happens because of changes in the brain. These include lower levels of chemical messengers ( neurotransmitters) that help brain cells work properly. What causes these changes is not clear.

The risk of getting Alzheimer’s disease increases as you get older. But this does not mean that everyone will get it. By age 85, about 35 out of 100 people have some form of dementia. ¹ That means that 65 out of 100 don't have it. Dementia is rare before age 60.

Having a relative with Alzheimer’s raises your risk of getting it, but most people with Alzheimer's disease do not have a family history of it.

What are the symptoms?

For most people, the first symptom of Alzheimer's disease is memory loss. Often the person who has a memory problem does not notice it, but family and friends do. But the person with the disease may also know that something is wrong.

As the disease gets worse, the person may:

• Have trouble making decisions.
• Be confused about what time and day it is.
• Get lost in places he or she knows well.
• Have trouble learning and remembering new information.
• Have trouble finding the right words to say what he or she wants to say.
• Have more trouble doing daily tasks like cooking a meal or paying bills.

The symptoms of Alzheimer’s get worse slowly over time. A person who gets these symptoms over a few hours or days or whose symptoms suddenly get worse needs to see a doctor right away, because there may be another problem.

As people with Alzheimer’s get worse, they may get restless and wander, especially in late afternoon and at night. This is called sundowning. Over time, they may also start to act very different. They may withdraw from family and friends. They may see or hear things that are not really there. They may falsely believe that others are lying, cheating, using them, or trying to harm them. They may strike out at others.