Since ancient times, it has been clear that some people lose mental sharpness (cognitive function) as they age. But it was not until 1906 that Alzheimer's disease was discovered. That year, German neurologist Alois Alzheimer (1864-1915) performed a neurological autopsy on the brain of a 56-year-old woman, Auguste D., of Frankfurt.

At the New York University Medical Center's Aging and Dementia Research Center, Barry Reisberg, M.D., and colleagues have developed the Functional Assessment Staging (FAST) scale, which allows professionals and caregivers to chart the decline of people with Alzheimer's disease.

During the 1960s, researchers considered Alzheimer's disease a rare disorder. But over the last 30 years, scientists have recognized that it's fairly common -- in fact, Alzheimer's is the leading cause of age-related dementia. Many famous people have had Alzheimer's disease: British statesman Winston Churchill, actress Rita Hayworth, and most recently, former President Ronald Reagan.

Today, the condition is known as Alzheimer's disease (AD), or dementia of the Alzheimer's type (DAT). Some experts are starting to drop the apostrophe "s," calling the condition Alzheimer disease (paralleling the name change from Down's syndrome to Down syndrome), but most authorities continue to use the apostrophe "s" -- Alzheimer's disease.

Alzheimer's disease is a brain disorder which gradually destroys the ability to reason, remember, imagine, and learn. It's different from the mild forgetfulness normally observed in older people. Over the course of the disease, people with Alzheimer's no longer recognize themselves or much about the world around them. Depression, anxiety, and paranoia often accompany these symptoms. Although there is no cure, new treatments help lessen Alzheimer's symptoms and slow its progression.