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Study: New Genetic Risks for Dementia in Black Americans

By | November 20th, 2020

The largest African American genome-wide association study to date has revealed new race-based genetic risk factors for Alzheimer’s. 

Alzheimer’s disease is more prevalent among Black Americans than among white Americans. By some estimates, it is 14% more common among Black Americans; by others, their risk is twice as high as their white peers. Environmental variables such as lack of access to healthcare and education, as well as increased risk of high blood pressure, high cholesterol and diabetes, all play into this disparity. Now, researchers are looking at another risk factor: racial differences in genetics.

Concurrent with new research examining genetics and dementia risk among Latinx populations, and with the launch of the new Center for Brain Health Equity, which aims to help representatively diversify historically white Alzheimer’s research, a genome-wide association study of unprecedented size has pointed researchers to several previously unknown genetic risk factors for Alzheimer’s among the African American population.

In the study published in the journal JAMA, scientists analyzed the data of 8,006 Black Americans, scanning of DNA to find genetic variations linked to Alzheimer’s: 2,784 of the participants had Alzheimer’s and 5,222 were controls. Participants had an average age of 74. 

While the researchers found that many of the genes differed from those identified in larger studies done in largely white participants, Alzforum reported, their functions such as immune response, processing of fatty acids, and the movement of molecules mostly overlapped. 

Though the researchers of the recent study discovered a novel pathway of these genes that involves kidney system development. 

“This finding is particularly interesting given the observation that African American individuals are three times more likely to experience kidney failure compared with the non-Hispanic White population,” the researchers wrote, “and along with Hispanic populations, have a higher rate of comorbidity for dementia and kidney disease.” 

Brian Kunkle, an author of the study and research assistant professor at the University of Miami, told Alzforum that this link highlights how genetics, comorbidities, and health care disparities may be interconnected and how they might exacerbate Alzheimer’s risk. 

The scientists say that their results have implications for predicting individuals’ chances of developing the disease: “In the future, we think that polygenic risk scores — which take dozens of genetic risk factors into account — can help us identify those most at risk,” Dr. Christiane Reitz, an author of the study and associate professor of neurology at Columbia University, said in a news release. “Our findings tell us that we likely will need different risk scores for different ethnicities, since the genetic risk factors vary somewhat from group to group.” 

While this study is the largest genome-wide association study on African Americans to date, Alzforum reported the study is still small by genome-wide association study standards. More research is needed, as many agree that the link between race and genetics in Alzheimer’s remains unclear: Earlier this year, the authors of the Alzheimer’s Association’s 2020 report stated that non-genetic factors — like medical conditions, health-related behaviors and socioeconomic factors — likely account for most of the disparity in Alzheimer’s risk among different racial groups.

Meanwhile, Reitz and colleagues are now developing studies with larger numbers of Black participants, she said, and the more researchers understand the genetic differences between populations, “the better we will [be] able to assess an individual’s risk for the disease and develop precision medicine approaches.” 

Contact Nicholas Chan at nicholas@beingpatient.com

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