Applying Mendelian Randomization to the Correlation Between Fitness and Health (opens in new tab)

It is a struggle to derive evidence for causation from human data. It is well established that physical fitness correlates with a lower risk of age-related disease and mortality in humans, and well established that greater physical fitness causes a lower risk of age-related disease and mortality in animal studies. But as a practical matter one can't run the sort of study that would be needed to obtain direct proof of causation in humans. So researchers turn to approaches such as Mendelian ran...