October 14, 1996
The degree to which Cherokee Indians are of pure ancestry or mixed ancestry may play a role in delaying the development of Alzheimer's disease after age 65. Research by National Institute on Aging (NIA) grantees at the University of Texas Southwestern (UTS) Alzheimer's Disease Center (ADC) reported in the October, 1996 issue of the Archives of Neurology (pages 997-1000) gives scientists yet another clue to the diverse nature of Alzheimer's disease. Coming on the heels of another NIA finding showing higher rates of Alzheimer's disease in Japanese men who emigrated to America as opposed to those who remained in Japan, this report gives credence to theories that ancestry, environment, and other factors play additive roles in predisposing a person to Alzheimer's disease.
Methods and Findings
Lead investigator Dr. Roger Rosenberg of UTS and Director of this NIA-sponsored ADC; Dr. Ralph Ricther, Director of the Alzheimer's Research Unit, St. John Medical Center, Tulsa, OK; and colleagues looked at a Cherokee Indian population in Northeastern Oklahoma and determined the degree of Cherokee ancestry and ApoE gene type in 26 people with probable Alzheimer's disease and in 26 controls. Depending on which of its three forms a person inherits, the ApoE gene may predispose people to Alzheimer's disease. Dr. Rosenberg found that, in this study population, people with Alzheimer's disease were more likely than the control population to be one-fourth Cherokee or less (38 percent versus 4 percent for the control population).
Similarly, 50 percent of normal controls reported three-fourths or greater Cherokee ancestry versus only 12 percent of those with Alzheimer's disease. This difference indicates the presence of some form of protection from Alzheimer's in those with mainly Cherokee ancestry. However, this apparent protection seems to diminish with age.
Implications
Dr. Rosenberg says the possible protective genetic effect seen in those people with a higher percentage of Cherokee heritage is separate from, but may be analogous to, the protective effect of the good type of ApoE, which may delay the onset of the disease in Caucasians. "Our results indicate the presence of a gene, or genes, separate from other identified risk factors, that is protective or preventive for Alzheimer's in this Native American population." Dr. Rosenberg also speculates, based on DNA evidence, that there may be a connection between lower incidence of Alzheimer's in Chinese men and Cherokee Indians.
Dr. Creighton Phelps, head of the ADCs program for the NIA, says, "In other studies, we're looking at lower rates of Alzheimer's disease in Japanese, Chinese, Cree Indians, and other peoples, compared to Caucasians. These recent findings make it likely that several different genes, as well as environmental factors, influence the development of Alzheimer's disease in different ethnic groups. We have to keep puzzling through these interesting leads until we find the additional factors that contribute to the development of Alzheimer's disease.
Scientific Collaborators
This scientific communication was accomplished thanks to a close formal collaboration between the authors; Dr. David Kingfisher, Executive Director, Health Services Division, the Cherokee Nation; and physicians working with the Cherokee Nation. Collaborating research centers include St. John Medical Center and University of Oklahoma College of Medicine, Tulsa; Health Sciences Division-The Cherokee Nation; H.A. Chapman Institute of Medical Genetics, Tulsa; and University of Washington Medical Center and Gerontology Service, Veterans Affairs Puget Sound Health Care System, Seattle.
