With this kind of observational study, we can’t really say exactly what lead to these differences. It’s easy to imagine why shortstops and second basemen, who have to be light on their feet, might be the healthiest players. Equally, the connection between catchers, who wear heat-trapping protective equipment and have baseballs aimed at their privates for 162 days out of the year, might have higher genitourinary disease issues. But to know more, we’ll have to study baseball players as a demographic in much more detail. We’re guessing plenty of data-loving (and sports-loving) scientists will be happy to do so.