User blog comment:18emerc/Superboy and his abilites/@comment-50.14.65.44-20130223013850/@comment-432124-20130225012224

If the League and STAR Labs were able to find any undisclosed side effect using all of their resources, don't you think that they would have been able to fix his aging condition by now?

As for the Atom, Plastic Man, Captain Atom, and the Flash, they're all fully human and they all possibly have meta-genes to protect them from the side effects of their powers. Thus, this wouldn't apply to Superboy and he might not be so fortunate.