[JSM_Liberty]

"played D1 and professional football, rugby for 5 years,"

Rugby is trying to reduce the number of head collisions. They come down hard on any tackle that makes head contact but I think that even tackles that don't make direct contact with the head can still cause damage. It is hard to prevent head movement in tackles or when you hit the ground.

[lepton]

It is still not clear what contacts or types of damage cause the damage that results in CTE, nor whether that is related to age when taking the damage.

As for self-selection, this study is extremely self-selected, so while informative in a general sense, we also have to recognize the current limitations and encourage something closer to a randomized sample.