This makes for firmly grim reading:
PFA-funded study of 8000 former professionals who played between 1930-1999 suggests outfield players (not goalkeepers) have around four times the risk of developing dementia than equivalent people who are not footballers, up to five times for those with long careers.
Most worryingly, no obvious drop off as balls become lighter and the game becomes a bit less aerial into the 90s.
https://www.thepfa.com/news/2021/8/2/dementia-risk-player-position-career-length?fbclid=IwAR30MZEOe93FhhODu_6AkZdkcjGsbUiJo3kWcjf4MtJElGVx4aAHo0ZntO4I don't know what the answer is (and ban heading is probably over-simplifying it) but that's pretty firm evidence of a link. Can consenting adults take the risk? Probably, same as for other injury risks, but it's important that people at least know what that risk is.