From what I've read, I doesn't seem that other sports have received the same level of scrutiny as has football since it was a former NFL player that the disease was first documented. They have also only tested the brains of deceased players who have donated their bodies to research because of the assumption/speculation that there was the possibility of CTE. In other words the research, while important, is very skewed. Only more testing of other sports and time will help unearth the far reaches of CTE.