[dloose]

Are we sure it's not prevalent? Concussions & CTE weren't widely reported in the NFL until recently. Googling for "rugby cte" turns up articles like this one (http://www.telegraph.co.uk/sport/rugbyunion/11857548/Rugby-u...), which suggest that it might be more of a problem than you're implying. It's even a problem in non-American football/soccer (source: http://www.businessinsider.com/soccer-heading-brain-damage-d...).

[roguecoder]

I suspect over the next decade, and especially as we develop better diagnostic tools, we will find more details about which sports have significant links and be able to effectively modify the rules (banning heading the ball, for example) or steer children towards the sports that don't.

Sports you wouldn't necessarily expect, like ice skating, have problems with concussions.