The Tsimane tribe of Bolivia seem to make a habit of confounding scientists. First, as reported in a previous blog, they have the healthiest hearts ever – despite living in a constant state of infection-induced inflammation. For years, scientists have been telling us that inflammation is bad for our hearts. Apparently not for the Tsimane. Now scientists find they experience a much lower rate of Alzheimer’s. Scientists also tell us that those of us who have a copy of the Alzheimer’s gene, ApoE4, have a higher risk of getting Alzheimer’s. Two copies increase the risk by 10%. For us, maybe, but not the Tsimane.
For the Tsimane, the ApoE4 gene seems to be helpful and tribe members rarely have dementia. Dr. Trumble of the Tsimane Project, showed that members of the Tsimane tribe who had either one or two copies of ApoE4, actually performed better on cognitive tests than those that did not have the gene.
Puzzled by this conundrum, Trumble, who knew that most tribe members had suffered from parasitic infections wondered if somehow these infections helped. The result — for those tribe members who had the ApoE4 gene, but never had an infection, the gene correlated to lower mental fitness. Studies of ancient bones show that the ApoE4 gene was nearly ubiquitous in our ancestors, and probably helped protect them from parasitic infections. But with no parasites to be found, the gene could be causing the brain to attack itself.
It seems that our extreme cleanliness habits have led not only to an increase in asthma and allergies, but Alzheimer’s too.
Researchers are hoping that the Tsimane may hold the key to the cure for Alzheimer’s. But they need to be quick – before our industrialized civilization destroys their way of life.