Scientists Assess Alzheimer’s Risk in Minority Populations

How susceptible is that American on the street to Alzheimer’s disease? Does he or she carry one of the three genes known to be inherited in an autosomal-dominant fashion and to be capable of triggering early-onset Alzheimer’s disease? Or does he or she carry a gene known to increase susceptibility to Alzheimer’s later in life—the so-called E4 version of the APOE gene?

Confounding the question further, how vulnerable is the person if he or she is Asian American? African American? Hispanic American?

These are tough questions indeed, but scientists are now starting to search for answers. Some of these scientists recently came together to discuss their nascent findings at a conference on the campus of the National Institutes of Health in Bethesda, Md. The conference, titled “Genetics, Clinical Response, and Cognitive Enhancers—Implications for Alzheimer’s Disease,” was cosponsored by APA, along with the National Institute of Mental Health and the National Institute on Aging.

The incidence of Alzheimer’s disease among the Japanese in Japan appears to be only half that of Caucasian Americans in the U.S., Kenneth Sakauye, M.D., a professor of clinical psychiatry at Louisiana State University in New Orleans and chair of APA’s Council on Aging, reported. The incidence in Japan, he explained, was calculated from autopsy results, so it was probably accurate, not just a best-guess estimate. Nonetheless, whether the incidence of Alzheimer’s among Asian Americans is the same as the incidence of Alzheimer’s among the Japanese in Japan is not known.

Hispanic Americans and African Americans may be somewhat more susceptible to Alzheimer’s than Caucasian Americans if a few studies reflect the truth, according to Jennifer Manly, Ph.D., an assistant professor of neurology at Columbia University in New York City. In fact, Manly and her colleagues conducted one of these investigations. They studied some 2,000 persons aged 65 years or older in an ethnically mixed community in New York City. The risk of Alzheimer’s in this group was found to be 15 percent among Caucasians, 25 percent among Hispanics, and 40 percent among African Americans.

In contrast, a study in Nigeria found a low incidence of Alzheimer’s there, Manly also pointed out. The incidence of Alzheimer’s among persons in Central American and South American countries has not been determined, reported Freddy Ortiz-De Jesus, a doctoral psychology student at the Fielding Institute in Santa Barbara, Calif. So whether African Americans and Hispanic Americans are truly more susceptible to Alzheimer’s disease than Caucasian Americans is really not known at this point.

In any event, even if African Americans and Hispanic Americans are more susceptible—which is by no means certain—one thing does seem pretty sure: It is not because they carry more of the E4 variant of the APOE gene than Caucasian Americans do. This finding comes from Manly and her colleagues.

If African Americans, Hispanic Americans, and Caucasian Americans all seem to have essentially the same incidence of the APOE-E4 gene variant in their populations, might one of these groups have a preponderance of some other Alzheimer’s gene? This is a possibility, especially since more Alzheimer’s gene candidates are looming on the horizon. As Lindsay Farrer, Ph.D., a professor of neurology and chief of the genetics program at Boston University, put it: If there is a race-specific gene that increases Alzheimer’s susceptibility, scientists have not fingered it yet.

Drug Response Same?

With regard to the question of whether Alzheimer’s drugs now on the market work the same in minority Americans as they do in Caucasian Americans, there is even less information, conference researchers disclosed.

Specifically, Thomas McRae, M.D., medical director of Pfizer Pharmaceuticals in New York City, reported that Pfizer has information on how some 4,000 patients from various countries have responded to the Alzheimer’s drug donepezil. Most of the patients have been Caucasian, but some have been Japanese, and the response of the Japanese patients to the drug is similar to that of the Caucasian patients. Thus it is possible that Asian Americans might react to Alzheimer’s drugs the same way that Caucasian Americans do. But this is certainly not known for sure.

And how about Hispanic Americans’ and African Americans’ responses to Alzheimer’s drugs? As Leon Thal, M.D., director of the Alzheimer’s Disease Cooperative Study at the University of California at San Diego, said, this is uncharted territory, but probably not for long. A major purpose of the conference was not just to bring scientists together to share data regarding minority susceptibility to Alzheimer’s and minority response to Alzheimer’s drugs, but to help them plot strategy for future research to answer these questions (Original article: see box).

Minority Subjects Needed

To uncover more information about minority susceptibility to Alzheimer’s disease and minority response to Alzheimer’s drugs, of course, scientists are going to need to get more minority patients involved in Alzheimer’s research. But will they participate?

Conference attendees agreed that while it is challenging to get minorities involved in medical research—because of language difficulties, transportation difficulties, cultural factors, and so forth—it is certainly not impossible. The best way to reach minorities, they concurred, was at the community level—say, through their primary care physicians, churches, senior centers, and so on. There is reason to think that once minorities are aware of Alzheimer’s research projects and the need for their participation, they will indeed want to get involved. So testified Robert Green, M.D., director of the clinical corps of the Boston University Alzheimer’s Disease Center, on the basis of his own experience in this area.

Not long ago, Green and his colleagues wanted to set up what is expected to be the first study on people’s psychological reactions to learning that they have a genetic susceptibility to Alzheimer’s disease. The researchers weren’t sure that people would be willing to take part in such a study, yet a number of people have expressed interest, Green reported. In fact, to date, he said, “41 people have stuck out their arms” to be tested for the APOE-E4 gene variant that increases Alzheimer’s susceptibility, and that includes minority Americans.

Green is looking for more participants for his study, whether minority or nonminority. Readers who know of any persons who might be interested in signing on are urged to call toll-free (888) 458-BUAD. ▪