ALZHEIMER'S DISEASE AFFECTS ABOUT 4 MILLION AMERICANS

QUESTION: Twenty years ago my grandmother died from what people now call Alzheimer's disease. What have we learned about the disease in recent years?

ANSWER: Alzheimer's disease is currently estimated to affect 4 million Americans, with approximately 250,000 new cases diagnosed annually. This progressive disease of the brain slowly deteriorates the mind and causes varying degrees of memory loss, disorientation and impaired thinking.Up to 20 percent of all Alzheimer's cases are believed to be familial, though the rest seem to be sporadic, or unrelated to hereditary factors. Early-onset Alzheimer's (usually occurring between the ages of 45 and 55) is frequent in familial cases. Sporadic Alzheimer's appears randomly, usually after age 65, and instances of it increase dramatically with age.

The National Institute on Aging (NIA) has been leading the federal initiative in Alzheimer's research and care. "The search for causes of this devastating disease, with particular attention to the genetic component, has been a priority in research on aging," says Dr. Gene Cohen, a psychiatrist and acting director of the NIA.

Recently, NIA-supported researchers found a gene mutation that may be responsible for nerve-cell death and resulting dementia associated with one form of Alzheimer's disease.

Dr. Merrill D. Benson and associates at the Indiana University School of Medicine and the Veterans Affairs Richard L. Roudebush Medical Center studied three successive generations of a family with Alzheimer's disease. The team identified a single mutation in a gene - which instructs the composition of amyloid precursor protein (APP), a common brain protein - that it believes could trigger Alzheimer's. "Discovering that the family members with the altered gene have Alzheimer's disease and those with the unchanged gene do not confirms our suspicious about hereditary Alzheimer's," said Dr. Zaven Khachaturian, associate director the Neuroscience and Neuropsychology of Aging Program at the NIA.

The team studied the DNA of 31 family members spanning three generations. Six of the subjects were affected with early-onset familial Alzheimer's disease. The same mutation in one section of the APP gene was found in each of these six subjects. In three members of the family, lesions characteristic of the disease were found in the brain tissue during autopsies. The lesion findings confirmed earlier diagnoses made by DNA analysis.