Bosh has a clotting disorder. He is at risk for ischemic stroke, pulmonary embolism, among others. Even though he is likely on a novel anticoagulant, among other medications, this treatment does not prevent clots from forming. It simply reduces the chance of it happening. Furthermore, anticoagulation puts him at risk when playing a contact, physical sport, as his chances for internal bleeding go way up. All this coupled with the fact that he hasn't played basketball in two years and is on the wrong side of 32, why bother? Medicine is a science. But it is not an exact science - it would be bad medicine to clear Bosh to play.