Researchers have known for a while that African Americans and Hispanics have higher rates of Alzheimer’s disease than whites do, though the reason(s) for this dementia disparity remained elusive. Now, for the first time, scientists have pinpointed a genetic mutation that may explain the higher risk for blacks.
According to the Alzheimer’s Association, older blacks in the United States are about twice as likely as older whites to have Alzheimer’s and other dementias; older Hispanics have about one-half times more risk.
“When differences between racial and ethnic groups are found, it is sometimes assumed that the differences must be due to genetic factors, but no known genetic factors can account for the differences in the prevalence of Alzheimer’s disease and other dementias among older whites, African-Americans and Hispanics,” the organization noted in a 2010 report.
Some doctors suggested that the higher rates of hypertension and diabetes in black Americans are behind the higher dementia rates; both are factors in Alzheimer’s disease as well as vascular dementias. ”Likewise, lower levels of education and other socioeconomic characteristics that are associated with increased risk … are more common in older African Americans and Hispanics than in older whites and probably also account for some of the differences,” according to the AA report.
Those explanations are still valid, but it turns out there’s a genetic component to this puzzle, also. A variant of the ABCA7 gene in African Americans seems to be responsible for increasing late-onset Alzheimer’s risk.
Black patients who had the ABCA7 gene variants (or “single-nucleotide polymorphisms,” as the scientists say) were 79% more likely to get late-onset Alzheimer’s disease, compared to those who didn’t. This is similar to the way a variant of the APOE gene (APOE4) increases Alzheimer’s risk for whites.
“We know that cholesterol is a risk factor for Alzheimer’s disease,” Huntington Potter, director of the Alzheimer’s Disease Program at the University of Colorado, told MedPage Today. “These genes affect cholesterol metabolism, and that may give us a new hint that before was only suspected about what causes Alzheimer’s disease.”
The study comes Columbia University and was published online in the Journal of the American Medical Association. The authors conclude that future ABCA7 and Alzheimer’s studies “may have major implications for developing targets for genetic testing, prevention and treatment.”