TUESDAY, April 9 (HealthDay News) -- A particular variant of a cholesterol-related gene may double the risk of Alzheimer's disease in older blacks, a new study suggests.
The gene -- known as ABCA7 -- is also linked to Alzheimer's among whites, but it appears much more important in blacks' risk of the memory-robbing disease, the researchers said.
Still, although a doubling in risk may sound large, the researchers stressed that it's actually a modest increase. Older adults' risk of Alzheimer's is thought to depend on many factors -- not only an array of different genes, but also environmental influences.
"How much does this increase your risk? It's modest," said Dr. Robert Nussbaum, a professor of medicine at the University of California, San Francisco, who was not involved in the study.
But the findings are important because they add to the understanding of the complex underpinnings of Alzheimer's, said Nussbaum, who wrote an editorial published with the study in the April 10 issue of the Journal of the American Medical Association.
The results come from what is believed to be the most extensive search yet for Alzheimer's-linked genes in older blacks.
Most of what is known about Alzheimer's genes has come from data on white adults, because until now there hadn't been a study sample of blacks that was large enough for a gene study, said study lead researcher Dr. Christiane Reitz, an assistant professor of neurology at Columbia University Medical Center in New York City.
Researchers have known for years that whites with a particular variant in the ApoE gene -- called ApoE4 -- have a higher risk of Alzheimer's than whites who carry other variants of the gene.
About 25 percent to 30 percent of the population is thought to carry the Alzheimer's-linked E4 variant.
In the new study, ApoE4 also was linked to an increased Alzheimer's risk among ne
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