Former England captain Alan Shearer believes more money should be invested into researching links between heading a football and dementia.
The 47-year-old has expressed his concerns about the effects heading a ball during his career may have on his long-term health and took part in BBC documentary 'Alan Shearer: Dementia, Football and Me' to investigate.
Shearer spoke to families of footballers affected by dementia and underwent various studies, while also looking at the brains of people who have suffered chronic traumatic encephalopathy (CTE) from all walks of life.
Speaking on the documentary, Shearer said: "Never ever did I think that heading a football could be dangerous for me.
"There are 850,000 people in our country that are suffering from dementia, and there are a lot of footballers who are in those numbers. But... we don't know how many and that can't be right.
"We started the research in 2002, it's now 2017 and it seems like we are no further forward because the same questions are still being asked.
"There's enough money around nowadays in football, just not enough of it has been given to research. It's about time we had more definitive answers."
Former Luton forward Matt Tees suffers from late-stage dementia, something his wife May feels has been brought on by the repeated action of heading a football, as she explained her struggles of living with someone with the disease.
"Matt is quiet, he doesn't talk. He doesn't know that this is his house. That is heartbreaking for me," she told the BBC documentary.
"I think I have learned to be strong, because I have had to be. We are in the final stages, it could be two years, it could be 10 years - nobody knows.
"There has to be (a link). I can name about eight people who have played football, in this area, who have dementia or Alzheimer's. So that speaks volumes in my opinion."
The former Newcastle striker looked at parts of the brain of ex-West Brom forward Jeff Astle, who died from CTE in 2002 aged 59, and whose family have campaigned to raise awareness around brain injury in football.
The Jeff Astle Foundation says it has been contacted by the families of more than 300 former players, including an increasing number ready to contribute to the creation of a 'bank' of donated brains to help investigate.
Dawn Astle, daughter of the former five-capped England international and founder of the foundation, told Shearer she believes football authorities are dodging responsibility for player welfare.
She added: "The PFA (Professional Footballers' Association) only exists for player welfare - they should be screaming from the rooftops for these players. This is killing our players and this should be their priority."
Gordon Taylor, chief executive of the players' union, admitted he did not know how many former players have the onset of dementia but wants to improve support systems for sufferers.
He said: "I think it is the PFA's job to look and provide support. We have said money is going to be put towards research and also respite care.
"Football has a duty to see if there is a causal link, because if there is, it could significantly increase the problems in later life then we need to look at the rules of the game and address it."
Press Association Sport understands a major study into whether footballers are at greater risk of degenerative brain disease is set for launch in the next few weeks with the appointment of a research group, jointly commissioned by the Football Association and Professional Footballers' Association.