I'm a concussion magnet. I've gotten several playing beer league, one from martial arts, one from... well, an emotional breakdown and it being self-inflicted (don't ask me to re-hash the details), and actually three from officiating. I've seriously contemplating giving up the game over it because I'm worried about
chronic traumatic encephalopathy, which is what they found after Derek Boogaard's death. I'd rather not be crippled and demented in my 40's like some of those retired NFL players are. That's a fairly unexplored area in medicine so far but it's still frightening to think about.
Regarding the earlier-discussed testosterone thing, I've been on hormone replacement therapy including a testosterone blocker (spironolactone) and it's definitely made it a more lengthy process to recover from illness and injury.