However, a new study has found no evidence that the high dementia risk among footballers is linked to health and lifestyle factors. Football increases the likelihood that heading footballs has caused brain injuries, BBC reported.

The research was led by Glasgow University s Professor Willie Stewart, who five years ago discovered footballers were three-and-a-half times more likely to die from a neurodegenerative disease than the normal population.

The study looked at the electronic health records of 11,984 former professional footballers and 35,952 matched individuals from the general population in Scotland.

Researchers compared key dementia risk factors across the two groups, including a history of smoking, depression, alcohol-related disorders, diabetes, hypertension, hearing loss and obesity.

Overall, the study team found that the rates of these risk factors were similar - or lower - among former players.

The Professional Footballers  Association, the trade union for professional footballers in England and Wales, has a dedicated brain health team to support former members concerned about brain health and educating current players on brain health in football.

"Our data suggests this relationship between higher rates of neurodegenerative disease among former professional footballers is not driven by those wider general health and lifestyle factors, widely recognised as dementia risk factors," said Professor Stewart.

A group of families - including relatives of the late 1966 World Cup winner Nobby Stiles - are taking legal action against football authorities over what they say are brain injuries caused by repeated impacts between head and ball.

Two former Premier League players - Gary Pallister and Steve Howey - have told BBC Sport of their health fears after years of heading footballs.

Howey, who is one of the claimants in the legal action, said he has undergone scans which have shown cognitive decline.

Leading campaigner Judith Gates, of Head Safe Football, has written to Culture Secretary Lisa Nandy to ask that heading the ball is declared a national health issue in order to safeguard players in the future.

Gates  husband Bill, a former Middlesbrough defender, died last year aged 79 as a result of Chronic Traumatic Encephalopathy (CTE). She founded the Head Safe Football charity to increase awareness of the danger of head impacts and signs of head injury.