Family History Has Complex Role in Alzheimer's Risk
Study Shows ApoE Genes Aren't the Only Factors in the Risk of Alzheimer's Disease
Family History and Biomarkers for Alzheimer's continued...
In people who had a family history of Alzheimer's, researchers found significant decreases in levels of beta-amyloid protein in spinal fluid. The lower level of beta-amyloid was true even if people didn't have an ApoE4 gene. There were no significant decreases in people who did not have a family history of the disease.
People in the study who had both a family history and who carried the ApoE4 gene had the largest drops in beta-amyloid in spinal fluid and had the biggest accumulations of beta-amyloid in their brains.
This suggests, experts say, that the presence of the ApoE4 gene is important, but that it doesn't tell the whole story.
Other Genes May Be in Play
Recent large genetic studies have uncovered several other genes that seem to be playing a role in the risk for late-onset Alzheimer's.
"Even though individually these additional non-ApoE risk factors might be quite small, if a family inherited several of them or different combinations of them, then it still can increase one's risk for these changes that relate to Alzheimer's disease independent of any effect of ApoE4," says study researcher John C. Morris, MD. He is a professor of neurology, pathology, immunology, and physical therapy at Washington University in St. Louis.
Morris says some of these genes share the same functions. Several are related to inflammation, for example, and he thinks they may be increasing risk by acting in concert with each other.
Other experts say there could be another explanation, too.
"Family history is not completely just genetics," says Brian Appleby, MD, a staff physician at the Lou Ruvo Center for Brain Health at Cleveland Clinic, Ohio. He was not involved in the research.
Appleby points out that families also tend to eat the same kinds of foods and share patterns of physical activity. And lifestyle is also thought to play a powerful role in Alzheimer's disease risk.
"It could be the way someone was raised and environmental factors and lifestyle factors. I think those things have to be considered, too."