Talk about getting hit to the head. Check this slo-mo video of a moderately hard hit to the head and then decide if you want this done a multiple times (never mind countless times in your fighting career) to your head - http://youtu.be/zYKpQuq4hsE.
I think the issues really start surfacing when you're old and decrepit as we're starting to see with retired American football players
That's my point.
It has to take a toll somewhere down the road.
But the sport hasn't been around long enough in order to determine that yet.
Even my (former) karate instructors are all banged up from years of hard training.
Knees, hips, backs, shoulders, neck. You name it.