Former professional footballers are three and a half times more likely to develop dementia than people of the same age range in the general population, according to new research.
Experts at Glasgow University have been investigating fears that heading the ball could be linked to brain injuries.
The study began after claims that former West Brom striker Jeff Astle died because of repeated head trauma.
It compared deaths of 7,676 ex-players to 23,000 from the general population.
However, despite the dementia risk, the study also found that playing the game increased average lifespan.
The long-awaited study, led by Dr Willie Stewart, began in January last year and was commissioned by the Football Association and the Professional Footballers' Association after delays in initial research had angered Astle's family.
Former England international Astle developed dementia and died in 2002 at the age of 59. The inquest into his death found heading heavy leather footballs repeatedly had contributed to trauma to his brain.
But research by the FA and the PFA was later dropped because of what were said to be technical flaws.
Astle's family has campaigned for the football authorities to launch a comprehensive research programme.
His daughter Dawn said she was "relieved" the study eventually went ahead, with her father's case highlighted by former England captain Alan Shearer in a BBC documentary Alan Shearer: Dementia, Football and Me.