What Happens

Researchers have discovered changes that take place in the brains of people who have Alzheimer's disease. These brain changes may cause the memory loss and decline in other mental abilities that occur with Alzheimer's disease. It's not fully understood why these brain changes occur in some people but not in others.

Alzheimer's disease always gets worse over time, but the course of the disease varies from person to person. Some people may still be able to function relatively well until late in the course of the disease. Others may lose the ability to do everyday activities very early on.

• The disease tends to get worse gradually. It usually starts with mild memory loss. It progresses to severe mental and functional problems and eventual death.
• Symptoms sometimes are described as occurring in early, middle, and late phases. It's hard to predict how long each phase will last. To learn more, see Symptoms.
• The average amount of time a person lives after developing symptoms of Alzheimer's disease is 8 to 10 years.

A person with severe dementia becomes more vulnerable to other illnesses, such as pneumonia.

What Increases Your Risk

Certain things make getting a disease more likely. These are called risk factors. Risk factors for Alzheimer's disease include:

• Getting older. This is the main risk factor. About 6 out of 100 people over 65 years and 35 out of 100 people over 85 years have some form of dementia.¹ People rarely have dementia before age 60.
• A family history of Alzheimer's disease, especially if one or more of your parents or siblings has the disease.
• The presence of the apolipoprotein E-4 gene.
• Having Down syndrome.