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An amino acid commonly found in the brains of Alzheimer's patients has been discovered in the spinal fluid of people without dementia whose close relatives were diagnosed with the disease, according to a study led by Duke University researchers.
The researchers also found people closely related to an Alzheimer's patient were more likely to have a smaller-than-normal hippocampus, the portion of the brain linked to memory. The findings could help lay the groundwork for development of early-detection tools, said Erika Lambert, a Duke researcher involved in the project.
"It's possible that these changes are among the reasons people with a family history of Alzheimer's are more likely to get Alzheimer's," Lambert said
People with a close family history of Alzheimer's — such as a brother, sister or parent — have a two- to four-times greater risk of developing it themselves.
The study, published last week in the online journal PLOS ONE, involved 257 people ages 55 to 89, all of whom had average memory functions or were considered "mildly forgetful," said P. Murali Doraiswamy, Duke professor of psychiatry and medicine and senior author of the study.
Each person in the study underwent cognitive assessments, as well as biological tests. Researchers found that about 50 percent of healthy people with a close family connection to Alzheimer's could be considered to have early signs of the disease, compared to only about 20 percent of people without a family history.
Memory loss significant enough to disrupt daily activities is a primary symptom of Alzheimer's, according to the Alzheimer's Association. About 25 million people around the world have Alzheimer's disease — a number that is expected to grow as the population ages. There is no cure.
Common genetic variations explain about 50 percent of the heritability of Alzheimer's, but other genetic factors influencing the disease remain unknown.
"So far we have been looking for genetic factors with big effects, but there might turn out to be a number of genes involved," Doraiswamy said.
The amino acid found in the subjects' spinal fluid is known as amyloid beta or Abeta, a component of the plaque buildup found in the brains of people with Alzheimer's disease.
Doraiswamy said people who have Alzheimer's in the family may want to consider volunteering for research studies to enhance scientific knowledge of the illness and also to reassure themselves about their own cognitive performance.
"If you want to help scientists make advances in the field, you could volunteer as a subject in research studies that involve regular testing of memory," he said. "That's also a way to get reassurance that your memory is normal."