Rugby players with brain damage are regularly being sent back onto the field of play because the sport’s governing bodies are not taking concussion seriously enough, medical experts said on Thursday.

The long-term risks of this could be higher rates of dementia, major depression and other neurodegenerative conditions later in life, the experts said, with evidence of such problems already being found among American football players who suffer similar rates of knocks to the head.

Barry O’Driscoll, a former International Rugby Board medical advisor who spoke to Reuters on the sidelines of a Rugby Football Union (RFU) conference on concussion, said he was in no doubt that injured players were going back into a dangerous environment.

“We are sending concussed players back onto the field - brain damaged players,” he said.

“We know now what’s going on in the brain as soon as it is hit. The glucose metabolism, the oxygen uptake, the electrolytes ... are all thrown completely out. This is a brain in disarray. It’s not functioning properly. The decision making is reduced, the cognitive function is reduced, and the emotions are thrown. What an earth is a person in that state going back onto the rugby field for?”

O’Driscoll resigned from the IRB last year in protest at the board’s attitude to concussion.

Martin Raftery, chief medical officer for the IRB, defended its position, saying the recent introduction of the Pitchside Suspected Concussion Assessment (PSCA) showed a commitment to player welfare.

“Ultimately the message to players, coaches and parents at all levels of the game is to recognize the symptoms of concussion and remove the player permanently from the training or playing field,” he said in a statement ahead of the IRB’s medical commission conference, due to start in Dublin, Ireland, next week.

Data presented at the conference show that concussion is currently the most common injury in the professional game, with between four and five instances for every 1,000 hours of rugby played. This compares with around 25 instances for every 1,000 hours of horse racing, and around 0.2 instances for every 1,000 hours of play in the NFL.

A growing body of scientific evidence, much of it resulting from studies of former NFL players and former boxers, suggests that repeated knocks to the head of the kind often experienced by rugby players, as well footballers and NFL and ice hockey players, can cause a condition known as chronic traumatic encephalopathy, which can lead to loss of cognitive function, dementia, aggression and depression.

Previous research has also found that former NFL players have higher rates of neurodegenerative diseases such as Alzheimer’s and Parkinson’s disease.

In a study published last month in the Nature journal Scientific Reports, British scientists said they had found “profound abnormalities” in the scans of brain activity of ex NFL players.

Will Skinner, the former captain of Harlequins who retired from rugby because of injury in mid-2013, said the emerging evidence about the possible damage inflicted by multiple knocks to the head he experienced during his playing career did give him cause for concern.

“We won’t know the ramifications until 20 years down the line so we’ll have to deal with that then,” he told Reuters. “But obviously if we can put in place procedures that mean my generation is the last to be affected - if we are affected - then that can only be a good thing.”

Skinner said attitudes to concussion both among players, coaches and team managers were changing. He praised the introduction of the PSCA, and said he’d like to see rugby authorities “erring on the aside of caution” until more evidence is available on the potential long-term harms.

But O’Driscoll and other medical experts such as Willie Stewart, a consultant neuropathologist at Glasgow’s Southern General Hospital in Scotland, say they fear the PSCA - essentially a five minute test often conducted in a pressured and adrenaline-fuelled atmosphere - is not enough to protect players who may have head injuries.

“The point is that suspected concussion is somebody showing signs, so they are concussed until you can prove they are better,” said O’Driscoll. “And you cannot do that in five minutes.”

Stewart, who also spoke at Thursday’s conference, said any doubt or suspicion about possible concussion should lead any team medic or coach to take a player off the field.

“Knowing what we know about American football, ice hockey and boxing and all these other contact sports, and with rugby being a very similar dynamic, I wouldn’t be in the least bit surprised if we found the same problems in rugby players,” he told Reuters. “The rule should be ‘if in doubt, sit them out’.”

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By Kate Kelland