It is a collection of symptoms characterized by decreasing intellectual and social abilities.

No single test identifies Alzheimer disease. Lab tests help rule out other disorders that may produce similar symptoms. Neurological and mental-status tests reveal cognitive-function deficits.

Nerve cells change in certain parts of the brain, which causes brain cells to die. The loss of cells impairs thinking and judgment.

Although some studies have shown an association between certain modifiable lifestyle factors and a reduced risk for Alzheimer disease, the National Institutes of Health says that age is the strongest known risk factor where most people receive the diagnosis after age 60. An early onset familial form can also occur, although it is rare.

Dementia can result from a variety of causes, but when Alzheimer is involved, dementia is irreversible and progressive.

Alzheimer sufferers also can't learn new information and tend to repeat themselves.

Help keep the person's body physically active and mind engaged as long as possible.

Alzheimer patients may live as few as 3 years or as long as 20 years with the disease.

The less change, the better.