advanced sideline technology and expanding medical resource. but sanjay, with players constantly getting hit, are there ways the sport could change to prevent brain damage? >> i think so, john. and i ask the researchers who've been doing this study. i talked to the chief health adviser for the nfl recently and they both say it is possible to make it a safer game and still have it be football. couple examples, first of all one of the worst consequences is if someone has a concussion and then is not taken out of the game. and they get a second concussion. that's called second impact syndrome. that can even be deadly in certain situations. so preventing that from happening. you've probably seen the sideline exams now taking place if you've been watching football. they're doing other things in terms of the rules as well trying to decrease the types of hits that are actually taking place. and also in practices not having blows over and over to the head. so helmetless practices for example. this particular study, these were players during their life