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.
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