Aging Siblings Offer Unique Glimpse Into Alzheimer's Disease

February 24, 2000

Siblings are about as close as people come, genetically-nearly all their DNA is identical. So why does one develop Alzheimer's disease while the other doesn't?

Such families offer an ideal mini-laboratory for physicians trying to trace the genetic roots of the disease. While scientists have identified nearly a dozen genes that can play some role in Alzheimer's, only about 5 percent of cases are clearly hereditary. The cause or causes of the other 95 percent, whether genetic or otherwise, go unexplained.

Now physicians at the University of Rochester's Strong Memorial Hospital are recruiting 100 sets of siblings from the Rochester area to study genetic differences between people who have been diagnosed with Alzheimer's disease and their siblings who have not. It's part of a national study sponsored by the National Institute on Aging, where 1,000 people from around the country will have their genes analyzed by physicians trying to clarify the role of genetics in the disease. In addition to the University of Rochester, patients will be recruited at Johns Hopkins, Harvard, Northwestern, and the University of California at San Diego.

"The genetic component of most major human diseases is complex and difficult to tease out," says neurologist Roger Kurlan, M.D., the lead Rochester investigator and chief of the Cognitive and Behavioral Neurology Unit at Strong Memorial Hospital. "There's probably an interaction between multiple genes, and there may be environmental influences as well.

"In heart disease, for example, it's well known that the interaction of genetics and lifestyle factors, such as diet and physical inactivity, is what makes people susceptible. It's the same with many forms of cancer, and it may be the case with Alzheimer's. We know that genetic factors are at work, but we don't know exactly how or to what extent."

In the study, thousands of each participant's approximately 100,000 genes will be screened, then compared to his or her sibling's genetic pattern for differences. Consistent differences among the 500 sets of siblings would give physicians strong clues about which genes might be involved in the disease. The genetic analysis will be done at Harvard under the direction of a Rochester alumnus, Rudy Tanzi, Ph.D.

Participants in the Alzheimer's study would make one short visit to Kurlan's clinic at the University of Rochester Medical Center. Siblings can make the visit either together or separately. Each will fill out a questionnaire, be evaluated by physicians, and have a blood sample drawn. There is no charge. Individuals who live outside Rochester and are unable to come in for a visit can also be included through special arrangements.

The Rochester group is also taking part in similar sibling studies of Parkinson's disease and Tourette's syndrome. For each of those studies, Kurlan's group is hoping to enroll 50 sibling pairs.

Anyone who would like to volunteer for the Alzheimer's study should call Anne Justus at (716) 275-0862.

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