Scientists investigating links between heading footballs and dementia say there is an urgent need for more research.
It follows the screening of a BBC documentary “Dementia, football and me”, featuring Alan Shearer.
Last year, scientists at Stirling University found just one session of heading a ball could lead to an immediate decrease in brain function.
They said more work was needed to assess long-term effects.
The academics have called for funding for further studies looking at the risks of heading footballs.
The BBC documentary, which was screened on Sunday night, heard from current and retired professional footballers, the relatives of former players diagnosed with dementia, the Football Association (FA), the Professional Footballers’ Association (PFA) and scientists in sports medicine.
Many of those interviewed raised concerns that there could be a link between heading the ball and brain health but said that more research was required.
The documentary included footage of former England international Shearer undergoing tests in a lab at Stirling, where academics have, for the first time, found direct evidence of brain changes immediately after heading a ball.
The FA and PFA have commissioned research into whether the degenerative neurocognitive disease is more common in ex-professional footballers than the rest of the population.
But cognitive neuroscientist Dr Magdalena Ietswaart and Dr Angus Hunter, reader in exercise physiology, said more funding was needed for scientific studies that would provide understanding of the risks associated with heading footballs.
Dr Ietswaart said: “We do not yet know whether there is a definitive link between football and dementia. This can only be discovered by carrying out research in this area.
“Scientific developments open up a new approach that is achievable but requires a robust funding drive. If you want real answers, you need to understand what is happening in the brain; what is cause and effect, the approach we use here at Stirling.
“Until now, we did not have sensitive or direct ways to identify how moving a ball with your head can impact brain health.
“However, we now have stronger neuroscience emerging that can look directly at what goes on in the brain as a result of heading the ball.”
She added: “We have applied these techniques here at Stirling but there is a lot more that we, and others, can do to give definitive answers on the dangers of heading.
“Current neuroscience has substantial promise in providing the evidence-base on the effects playing football has on brain health that is currently lacking.”
The tests undertaken by Shearer showed immediate brain changes after heading the ball – the same changes observed in participants who took part in the landmark study.
The research, published in EBioMedicine, is the first to show direct evidence for short-term sub-concussive changes in the brain following any sport-related impact.
After meeting the Stirling team, Shearer said: “Football should be encouraging these universities to do as much research as possible but, like everything else, these universities need funding.
“There’s enough money around nowadays in football but not enough of it is being given to research. It is about time we had more definitive answers.”
Dr Hunter said: “As conveyed by the BBC documentary, our study is the first to show changes in brain function after heading the ball.
“Combined with the anecdotal evidence, our research and this documentary should provide the stimulus for further scientific research to be carried out in this area.”
The research was funded by the National Institute of Health Research.