A web of correlations exist between wealth, education, intelligence, and natural variations in human longevity. It is thus interesting to see that one of the genes associated with longevity and aging also has an effect on cognition - though not the effect that was initially expected:
Scientists have known for more than a decade that people and animals tend to live longer if they have high levels of Klotho in their bodies. And that led [researchers] to wonder whether a hormone that protects the body against aging might also protect the brain. So the team set out to see whether Klotho offered a way to "prevent the cognitive decline that comes with aging."
To find out, they studied more than 700 people between the ages of 52 and 85. About 1 in 5 of these people had a form of the Klotho gene that causes their bodies to produce high levels of the Klotho hormone. The team expected to find that people with high levels of the hormone experienced less cognitive decline than people with lower levels. "In fact what we found was not consistent with our hypothesis. We were completely surprised."
What they found was that the people with lots of Klotho experienced just as much cognitive decline as other people. Their brains weren't protected against aging at all. But their brains were different nonetheless. "Those that carried the genetic variant that increased their Klotho levels showed better cognitive performance across the lifespan." At any given age, people with lots of Klotho scored higher on tests of learning and memory, language and attention.
To learn more, the team began studying mice that had been genetically engineered to produce high levels of the mouse version of Klotho. "Elevating klotho made the mice smarter across all the cognitive tests that we put them through." A look at the brains of these mice suggested a reason. There was evidence that in areas involved in learning and memory, Klotho was causing a change that strengthened the connections between brain cells.