The math for anyone who has any other option in life is pretty simple: You have exactly one brain, but more than one way to make a living.
OK, as I responded to the other person who doesn’t understand statistical bias: the documented causes of brain trauma you will encounter in everyday situations are disqualifying for most activities. And if you drink alcohol, you are destroying irreplaceable parts of your neuroanatomy with every drink. Those things risks are KNOWN. The risk from football remains unknown. Indeed, his quitting now may even be pointless if the entire pathology begins in developmental stages of life.