Malcolm Gladwell's new article about head injuries in NFL and college football players is gripping as always. Long term brain trauma has long been known to be prevalent in former boxers, too, but since the sport remains popular people still engage in it. Hits are worse when individuals aren't prepared. There's a debate in the academic lit as to how big of an issue this is for soccer players. Concussions among pro's occur at a rate of ~ 0.5 per 1000 player hours, usually due to elbow to head contact or head to head contact in "heading duels." I can tell you that when I used to play soccer I dreaded heading the ball back off of long goalie punts. Apparently the damage is worse when you fail to time it right and tense up your neck correctly. Here's one breakdown for how players were concussed during basketball:
How do you get a concussion running without the ball or during warm-up!?
Binge drinking should probably be considered a contact sport too, because the odds ratio for brain trauma among individuals with a BAC of 200+ mg/dl (around 10 drinks for 190 pound person) rises to 9.23! This is mainly due to a higher risk for assault (likely just fights in general), biking accidents, and simply falling. Be careful out there.