The degenerative damage potentially caused by repeated blows to the head in soccer has been highlighted by a rare study of brains of a small number of retired players who developed dementia.
Fourteen former players were part of the research that began around 40 years ago and six brains, which underwent post-mortem examinations, had signs of Alzheimer's disease.
Four brains were found to have chronic traumatic encephalopathy (CTE) pathology, a possible consequence of repeated impacts to the brain, including heading the ball. A previous study of 268 brains from the general population in Britain found a far lower CTE detection rate of 12 per cent.
The small sample size of former footballers prevented researchers from University College London and Britain's National Hospital for Neurology and Neurosurgery from drawing any conclusions about the dangers posed by playing soccer as they released their research.
But researchers hope the findings provide the impetus for more substantial studies in conjunction with soccer authorities. The researchers require current or retired players to be willing to take part of investigations that could take decades to produce conclusions.
"Our findings show there is a potential link between repetitive head impacts from playing football and the later development of CTE," lead author Dr Helen Ling of the UCL Institute of Neurology said.
At least four members of England's 1966 World Cup-winning squad have developed dementia or memory loss.
In the United States, there has been a $US1 billion ($A1.3 billion) settlement between the NFL and thousands of its former American football players who have been diagnosed with brain injuries linked to repeated concussions.
