Borrowed Time: The Science of How and Why We Age

by Sue Armstrong

A mass of data has also been collected over the years on the Amazonian people's cognitive function, and this is beginning to reveal some very interesting findings about the interaction of genes and environment. Among the Tsimane, APOE e4 – considered the highest single risk factor for Alzheimer's disease in the industrialised world, as we have seen – appears to protect the brains of those who have a high burden of parasitic infections. What's more, this benefit seems to kick in very early: Tsimane children who carry a copy of the APOE e4 gene are generally brighter than those who don't. This mirrors findings from other studies among kids in poor communities in Mexico City and Brazil, who are especially vulnerable to infection, and where those carrying the e4 gene variant seem to have better cognition.