Alzheimer's disease (search) is a progressive, neurodegenerative disease characterized by language deterioration, memory loss, personality changes and poor judgment. Alzheimer's is a form of dementia, a condition that impairs intellectual and social functions.

It is typically diagnosed after age 65. However, the onset can occur as early as mid life. Often symptoms such as loss of concentration and forgetfulness are mistaken as signs of old age or depression rather than a neurological disorder.

No two cases of Alzheimer's are alike — patients progress at their own rate, some more rapidly than others.

As many as 4 million Americans suffer from Alzheimer's. There is no cure, although medications are available to help to control the behavioral symptoms: wandering, depression and restlessness. Other medications can also be used to ease cognitive symptoms.

In the past five years, scientists have made great strides in understanding Alzheimer's disease. One scientific study even led to the discovery of the genes associated with it. This new knowledge may lead to treatments that could prevent, or block, the progression of Alzheimer's.

Samantha Jonas contributed to this for Foxnews.com.