While some gerontologists argue against "dementing" gerontology, emphasizing dementia in scholarly and popular approaches to aging, it cannot be doubted that the impact of progressive degenerative neurological diseases in old age is enormous and warrants attention. This year, two important breakthroughs were announced in Alzheimer's and Parkinson's diseases.
An international team of investigators studied a series of eight kindreds with familial Alzheimer's disease and isolated a genetic defect on the 21st chromosome.1 This is the first chromosomal evidence confirming the epidemiologic link with Down's syndrome. Clinically, persons with Down's syndrome often suffer progressive dementia in middle age and have brain lesions identical to those of Alzheimer's disease found at autopsy.
A second international team cloned a DNA probe for β-amyloid protein, which makes up the extracellular deposits in the brains of patients with Alzheimer's disease. By the use of this DNA probe, they established that the gene for the