Footballers could be risking dementia by suffering repeated minor injuries when they head the ball.
A study of 14 retired footballers found four had a condition known to cause dementia, while six had Alzheimer’s disease.
Repeated blows to the head suffered on the field, from headers and colliding with other players, are thought to be the cause.
It comes 15 years after the death of England striker Jeff Astle, whose inquest suggested he developed dementia as a direct result of heading heavy leather footballs. The Football Association has recently been urged to consider a ban on children under 10 doing headers in training and matches.
A team from University College London studied 13 professional footballers and one amateur player, examining the brains of six after their deaths. They found four had chronic traumatic encephalopathy (CTE), which can cause dementia and has also been found in boxers and rugby players.
Footballers may be far less likely to suffer a concussion than boxers, but experts say there is ‘evidence accumulating’ that repeated mild head trauma can lead to brain damage which can cause or worsen dementia.
Lead author Dr Helen Ling, from UCL’s Institute of Neurology, said: ‘Our findings of CTE in retired footballers suggest a potential link between playing football and the development of degenerative brain pathologies in later life.’
She added: ‘These players had the same pathology as boxers.’
The ‘pressing question now’, she said, was to determine how widespread the condition was among retired players.
‘It is important to note that we only studied a small number of retired footballers with dementia and that we still do not know how common dementia is among footballers,’ she said.
The first study to find CTE in retired footballers follows the news that three of the nine surviving members of England’s 1966 winning World Cup team are living with Alzheimer’s.
Last month the son of one of them, Nobby Stiles, criticised the FA for failing to properly investigate a link between the sport and degenerative brain disease.
Researchers at UCL studied retired footballers referred to the Old Age Psychiatry Service in Swansea between 1980 and 2010, all who started playing and heading the ball in their childhood or early teens – and all had dementia.
These men had a far higher rate of CTE in their brains than the 12 per cent average in the general population, based on a previous study of 268 brains. The condition, like Alzheimer’s, causes tangles of a protein called tau, believed to lead to dementia.
Dr Elizabeth Coulthard, consultant senior lecturer in dementia neurology at the University of Bristol, said the study was ‘detailed and robust’, although small.