CHICAGO (AP) — Blacks and Hispanics have a puzzling, additional risk factor that makes them much more susceptible than whites to Alzheimer’s disease, researchers say.
It’s been known since 1992 that people with a certain gene have a greatly elevated risk for developing the disease.
Now, researchers say that even without that suspect gene, blacks and Hispanics are at much greater risk than whites for Alzheimer’s.
“We think it’s another biological factor, another gene or genes that account for this,” said Dr. Richard Mayeux, a neurologist at Columbia University and one of the researchers in the study published in Wednesday’s edition of The Journal of the American Medical Association.
About 25 percent of the total population has the apolipoprotein E-4 gene, or apo E-4, which is known to be closely associated with the disease, although its exact role remains unknown.
The survey of 1,079 elderly men and women found that blacks who lack the gene are four times more likely to get the disease than whites. The risk to Hispanics is double that of whites. In both cases, the influence of age, gender, education, hypertension and family history of dementia was ruled out.
About 10 percent of the white population lacking the gene would be expected to get the disease, Mayeux said.
Blacks and Hispanics already were known to have higher rates of developing the disease, although the exact numbers are not firm and have been disputed, he said.
Other researchers not associated with the study said the results suggest that “being an African-American may be one of the strongest risk factors for AD yet observed.”
An estimated 4 million Americans have Alzheimer’s and 100,000 die of it every year.
The 1,079 subjects of the survey were Medicare recipients living in New York City. At the start of the study, none was diagnosed with Alzheimer’s. During follow-up exams, symptoms of the disease developed in 221 people.
With the apo E-4 gene, the rate of Alzheimer’s disease was about 30 percent across racial and ethnic lines, said Mayeux.