The genetic underpinnings of Alzheimer's disease have begun to emerge in recent years, only to reveal that the disease is far more complex, the responsible genes far more elusive, than was hoped. Statistical analyses of pedigrees affected by the disease suggest that at least two chromosomes play a role. The actual genes on these chromosomes, however, are still hidden in stretches of DNA 5 to 10 million base pairs long—a virtual universe left to search.
Also emerging is a new way of thinking about the disease. Many experts now suggest that what is called Alzheimer's disease may not be a "disease" at all, but a natural part of the aging process.
The theory stems in part from the observation that the brains of elderly persons who are unaffected by Alzheimer's disease also display the hallmark plaque deposits and neurofibrillary tangles found in the brains of patients with Alzheimer's disease, but