African-Americans with a particular gene are twice as likely to develop Alzheimer’s disease in old age as those without it, says a new study published in the Journal of the American Medical Association. This finding is a result of the largest database search for Alzheimer’s genes among African-Americans.
“Until now, data on the genetics of Alzheimer’s in this patient population have been extremely limited,” said Dr. Richard Mayeux, chair of neurology at Columbia University Medical Center and senior author of the study.
Alzheimer’s disease is the most common cause of dementia — a brain disease that affects memory, personality and the ability to reason. At age 65, only one percent of people have Alzheimer’s, yet over 80 years of age, it increases to 30 percent.
A new discovery
A gene called APOE is associated with one in every five cases of Alzheimer’s – known to be a major genetic risk factor for whites and blacks. Yet, in this new research, Mayeux and his team identified an additional gene variant linked to a doubled risk in African-Americans alone, called ABCA7.
“ABCA7 is the first major gene implicated in late-onset Alzheimer’s among African-Americans,” said Dr. Christine Reitz, assistant professor of neurology and lead author of the study.
To reach this conclusion, researchers examined samples from nearly 6,000 African-American men and women collected between 1989 and 2011 – 2,000 had a diagnosis of probable Alzheimer’s disease and the other 4,000 had no cognitive difficulty.
“Although this is a very significant finding, it does not change much for the everyday African-American male or female,” says Rick Kittles, PhD, a human genetics expert who has traced the ancestry of more than 100,000 African-Americans. “There is still much work to do [to] determine how exactly this gene plays a role in Alzheimer’s disease.”
Kittles is also an associate professor at the University of Illinois-Chicago, where he runs the UIC Institute of Human Genetics.
“It is likely that other genetic and non-genetic factors are playing a role,” he adds.
More work to be done
Since the ABCA7 gene is involved with the production of cholesterol in the body, it suggests that Alzheimer’s in African-Americans may be more affected by cholesterol levels than whites. It is also associated with the production of amyloid, a protein that makes up most of the plaques found in the brains of those with Alzheimer’s.
However, the experts caution that widespread genetic testing for Alzheimer’s is still years away.
“We are not yet at the point where we can take what we know about Alzheimer’s genes and come up with an accurate risk assessment,” Mayeux said.
The next step is to replicate the study looking for similar results, Kittles says. However, this may be tricky, as there are not many African-Americans enrolled in genetic studies.
Dr. Tyeese Gaines is a physician-journalist with over 10 years of print and broadcast experience, now serving as health editor for theGrio.com. Dr. Ty is also a practicing emergency medicine physician in New Jersey. Follow her on twitter at @doctorty or on Facebook.