But such a study is impossible to do.
Some would take issue.Gerald Ford played football at Michigan w/o a helmet. Didn't seem to hurt him too bad.
Children who take up American football early 'at greater risk of brain impairment': Boston University researchers find those who start playing before 12 twice as likely to develop emotional and cognitive difficulties as those who start later
https://www.theguardian.com/us-news/2017/sep/19/children-football-brain-study-boston-university
Some would take issue.
Here is a counter-point to some of the CTE claims recently - https://sports.yahoo.com/im-brain-scientist-let-son-play-football-135727314.html
It will be decades before we truly know how risky football (under the current set of rule) really is. By way of example, in my playing experience, practices for youth football and high school football were often brutal (whereas practices at wake had significantly less contact during the season). Today, with all of the rule changes - my son plays high school football in NC, and by rule, they are only allowed to have full contact in practice a maximum of 1 hour per week (and they rarely come close to that). Watching games on Friday nights, the game has 'deteriorated' some from a tackling perspective (because teams rarely practice it), but the game is still pretty much the same.
So let's say 30% of kids who play football at a high level get CTE later in life, is that OK? Is that worth the risk?
Would you let your kid do something that has a 30% chance of landing them in a wheelchair? Or give them a debilitating disease?
Stop telling people how to raise their kids when you've never come close to having your own.
Juice, A Brain Never Used