People with strong Cherokee bloodlines appear to have a lower risk of Alzheimer's disease than do people of Caucasian ancestry, according to a pilot study in the October Archives of Neurology.
Neurologist Roger Rosenberg of the University of Texas Southwestern Alzheimer's Disease Center in Dallas and colleagues compared 26 people from northeastern Oklahoma tentatively diagnosed with Alzheimer's disease with 26 others who showed no signs of dementia. Noting each person's percentage of Cherokee ancestry according to records kept by the Cherokee Nation, the team measured blood levels of three forms of apolipoprotein E (apoE), a molecule that ferries fat in the blood and which has been linked to varying degrees of risk for Alzheimer's disease.
To their surprise, the researchers found that the type of apoE gene had no bearing on Alzheimer's risk, while Cherokee blood did. The 26 healthy individuals were more likely to be three-quarters or more Cherokee, while those in the group with dementia were much more likely to be one-quarter or less Cherokee. Putting it another way, says Creighton Phelps, a neuroscientist at the National Institute on Aging, "the more Caucasian [blood] that gets mixed into the tribe, the greater the risk for Alzheimer's."
Earlier work by other researchers has shown that another tribe, the Cree, has a reduced risk of Alzheimer's disease, as do Chinese residents of Hong Kong, who are thought to share a common Asian ancestor with native Americans. Coupled with these findings, the Cherokee study suggests that apoE isn't the only genetic risk factor for Alzheimer's. "We're almost certain there must be other [genetic] risk factors, says Phelps. "We just haven't identified what those factors might be."