Alzheimer disease is the leading cause of dementia among older people. An estimated
10 percent of Americans over the age of 65 and half of those over age 85 have Alzheimer's.
More than four million Americans currently suffer from the disease, and the number
is projected to balloon to 10-15 million over the next several decades. Alzheimer's
is now the third most expensive disease to treat in the U.S., costing society close
to $100 billion annually.
In the popular imagination, Alzheimer disease is equated with an impaired memory,
but the disease includes a number of other changes in brain function that result
in inattention, disoriented behavior, altered personality, difficulty speaking and
comprehending, and impaired gait and movement.
Alzheimer's is a progressive, incurable disease. The earliest damage occurs in the
entorhinal cortex, hippocampus and basal forebrain, which are small, specialized
structures in the brain that play a critical role in memory. The disease is characterized
by amyloid plaques (deposits in the brain of a sticky protein called amyloid
beta peptide) and neurofibrillary tangles (abnormally twisted forms of the
protein tau, in the long branches of neurons). The cause remains a mystery.
Over time, the disease destroys large areas of the brain, leaving its victims with
little comprehension or awareness. As the disease advances, patients become incontinent,
bedridden and unable to feed themselves. From the onset of symptoms, the disease
runs its course in from two to 15 years. Seven years is the average extent, but
patients may survive as long as 20 years. Alzheimer's always ends in death, typically
from pneumonia or lack of nutrition.