ABSTRACT
Alzheimer's disease (AD) is a neurodegenerative disorder that currently affects more than four million people in the United States and perhaps 15 million individuals worldwide. I ,2 The disease is associated with atrophy/death of neurons in specific brain regions and occurs in two forms: an early-onset form that is primarily genetically determined, and a far more common late-onset form that is not. In its early stages, the disease manifests itself in the form of minor memory loss and progresses to major cognitive dysfunction. This latter may take the form of behavioral disorders, loss of orientation, language difficulties, and/or other attributes.3,4 The rate of progression to cognitive dysfunction varies among affected individuals but can be two decades or more; death in late-onset AD patients occurs from secondary causes, not from the disease itself. The incidence of sporadic AD increases with increasing age, and it is currently thought to be the most significant single cause of senile dementia.l,s Indeed, as many as half the total cases of dementia in the elderly may be attributable to AD. Essentially the only risk factor identified and generally accepted as valid for lateonset disease is possession of the APOE 84 allele on chromosome 19, although how this gene product engenders the neuropathology characteristic of AD is poorly understood at present.6 Not all patients expressing the 84 allele develop AD, but its presence appears to increase risk for the disease; the allele is also associated with earlier disease onset and rapid progression to cognitive dysfunction.
