The cumulative effect of years of heading the ball and accidental clashes of heads may cause long-term brain damage similar to that suffered by boxers, argues Dr Jon Spear, a consultant in geriatric psychiatry whose research has the backing of the Alzheimer's Disease Society.
In the latest edition of the International Journal of Geriatric Psychiatry he reviews international research relating to head injuries and football. He found that damage to and shrinkage of brain tissue were more common in professional footballers than other people. Repeated injuries can lead to pathological changes in the brain similar to those in Alzheimer's - a recognised hazard for boxers.
Dr Spear, a former lecturer in old age psychiatry at the United Medical and Dental School, London, who now works in Australia, said: "A football weighs about 400 grams [almost a pound] and can travel at up to 80 miles an hour. This creates a significant force on impact with the head. Football players are also susceptible to concussion as a result of the clash of heads. The long-term effects ... are not known."
He said Norwegian studies showed that professional footballers were twice as likely as others to show deficits in concentration, memory and judgement.
Dr Spear began his study after the death of the former Spurs captain Danny Blanchflower of Alzheimer's at the age of 67 in 1993. He suggests footballers should not play for a month after a severe blow to the head.
Professor Elaine Murphy, editor of the International Journal of Geriatric Psychiatry, said: "Former players who were heading the ball when it was made of leather and much heavier than today, especially when wet, may be at greater risk than today's footballers. Nevertheless, there is real cause for concern. Heading the ball exerts a shearing force on the brain, similar to a punch. If I was a professional footballer I would be concerned to know the facts." She said she did not believe the football authorities took the problem sufficiently seriously.
Les Helm, Everton's physiotherapist, said yesterday that he believed professionals were at less risk than amateurs. "I have full control over the players," he said. "If I say someone needs to go to hospital, they go. Amateurs may be knocked out for a couple of minutes, then get up and go on with the game. Anyone who is knocked out must go to hospital straight away.
Tony Cascarino, the Ireland and Marseille striker, said: "Even if there was proof I doubt if it would make much difference. It's a risk people are prepared to take. They think of their careers and carry on taking the money."
No members of the FA's medical committee were available for comment last night.