Nat Lofthouse, Tommy Lawton, Willie Thornton (think of all those Waddell crosses) didn't suffer from dementia as far as I know nor does Jimmy Millar.
Another great header of the ball, Willie Bauld of the Hearts, died very young but I don't know what he died of. Jeff Astle of WBA died at sixty and he definitely had brain disease which at the time was related to his football career.
On the other hand I can think of plenty defenders who liked nothing better than heading the ball clear for ninety minutes who thankfully are still with us.
Talking of the fearless Jimmy Millar of the Rangers wearing number 9, go to youtube and look for "Jimmy Millar of the Rangers" by the Followers. These days, nostalgia is even better than it used to be.