The question I have is what is the incidence of CTE in the NFL compared to CTE in other sports or professions?
Also, while it is possible that the trauma occurred while in the NFL, how much occurred in college or younger?
Furthermore, might the NFL have less of an issue if the helmets were more like the old leather helmets, so that the defense would have to tackle without using their heads, and that running backs would not duck when taking hits, similar to what happens in rugby?
Good questions- not easily answered.
CTE is probably akin to dementia pugilistica which occurs in about 20% of professional boxers. Other sports have not been studied as well. Relative rates of concussive injuries may provide some guidance but not definitive.
Trauma certainly could have occurred earlier as well. There is some evidence to suggest that concussions occurring in the early teenage years or before may be more significant than those occurring later on
Possibly- anything reducing impacts on the skull and concussions would likely help.