Thousands of Australians will get concussed playing sport this weekend and it will go mostly undiagnosed, untreated and unreported, the head of Brain Injury Australia, Nick Rushworth, says.
He said 3000 people a year were taken to hospital after being concussed playing sport. But this was the tip of the iceberg.
"Up to triple that number won't seek medical attention and as many as 10 times that number won't even report their concussion to teammates, coaches or family because they fear being removed from play," Mr Rushworth said.
Even among those who went to hospital because they "felt funny" or were suffering persistent headaches, most would not necessarily tie the problems to a head injury on the playing field.
Mr Rushworth, who has prepared a policy paper for the federal government on concussion in rugby league, rugby union and Australian football, said figures for concussions that did not result in hospitalisation were inexact and based on US data.
But the problem was large, ignorance widespread, and the risks serious, he said.
"Returning to sport before the brain has recovered puts the player at risk of long-term brain damage," he said.
However, the policy of a three-week exclusion period for concussed players, now abandoned by the international rugby code, was probably counter-productive, he said.
"There was good evidence it discouraged disclosure," Mr Rushworth said. What was needed was for concussed players to be removed from the field and individually assessed by a doctor familiar with concussion. The only treatment was rest, with the period determined by the doctor.
He said the further away from the elite level - in amateur and junior ranks - the more lax was the concussion management regime.
As well, the "macho culture" in sport meant players felt they needed to return to training the next day to keep their place in the team.
Rob Reid, of Sports Medicine Australia, said Australians did not take concussion seriously enough.
"Most people still believe you've got to pass out to be concussed or that wearing padded headgear is going to prevent concussion," Dr Reid said.
Immediate signs of concussion were being unsteady on the feet, being dizzy or light-headed and glassy-eyed. Sometimes players could not answer basic questions such as naming the ground they were playing on.
Former rugby player Jeremy Wilcox, who played in the premier division in the Australian Capital Territory, said he was concussed 15 times, nine times in the last three years of his career.
Wilcox played for more than 10 years from the late '80s.
"The more I got concussed the more normal it felt," he said. Now he says his short-term memory is affected and he has lost his sense of smell and taste.
With Brain Injury Awareness Week kicking off at the end of the month, Mr Rushworth is calling for a national concussion education program aimed at coaches, administrators, players and parents.