Alzheimer's disease is a progressive brain disorder named for German physician Alois Alzheiemer, who first described its symptoms in 1906. Since that time, however, understanding of the disease has grown substantiallyto the point where researchers now know a great deal more about risk factors, warning signs, and treatments.

The most common form of dementia, Alzheimer's destroys brain cells, causing problems with memory, cognition, and behavior that may become severe enough to affect one's ability to carry out simple tasks. Here, a look at the disease by the numbers.

  • More than 5 million: Number of Americans living with Alzheimer's disease, according to the Alzheimer's Association.

  • 10%: Segment of total sufferers who display symptoms before the age of 65, which is known as early-onset Alzheimer's.

  • 51: Age of the first patient diagnosed with what would later be called Alzheimer's disease.

  • 7: Number of stages of Alzheimer's disease, ranging from stage 1 (normal function) to stage 7 (severe or late-stage).

  • $148 billion: Annual direct and indirect costs of Alzheimer's and other dementias, according to the Alzheimer's Association.

  • Every 72 seconds: How often someone in the U.S. is diagnosed with Alzheimer's.

  • More than 50%: Estimated percentage of people who will develop symptoms of Alzheimer's disease by age 85.

  • More than $200 million: Amount of money raised from the Alzheimer's Association Memory Walk since 1989.