(CNN) - Several former NFL players called Thursday for an end to tackle football for kids ages 13 and under.
Pro football Hall of Famers Nick Buoniconti and Harry Carson joined four-time Pro Bowl linebacker Phil Villapiano and researchers from Boston University to make the announcement. They're working with the Concussion Legacy Foundation to support a new parent education initiative, Flag Football Under 14, that pushes for no tackle football until the age of 14.
"I beg of you, all parents to please don't let your children play football until high school," said Buoniconti, 77, who has been diagnosed with dementia and probable chronic traumatic encephalopathy, a neurodegenerative disease.
"I made the mistake starting tackle football at 9 years old. Now, CTE has taken my life away. Youth tackle football is all risk with no reward."
Buoniconti helped the Miami Dolphins to three straight Super Bowl appearances, including two wins and an undefeated season in 1972, the only such season in all of NFL history. In November, he said he intended to donate his brain to research.
New York Giants legend Carson echoed Buoniconti's sentiments.
"I did not play tackle football until high school, I will not allow my grandson to play until 14, as I believe it is not an appropriate sport for young children," Carson said.
Villapiano is best known for his big plays for the Oakland Raiders. He said that witnessing how CTE ravaged his teammate and friend Ken Stabler is causing him to speak out about the dangers of tackle football for children under 14.
"At some point, those of us who have had success in this game must speak up to protect both football players and the future of the game, and supporting 'Flag Football Under 14' is our best way to do that," he said.
How CTE begins
The players, along with researchers Chris Nowinski of the Concussion Legacy Foundation and Dr. Robert Cantu and Dr. Lee Goldstein of Boston University, pointed to studies that showed CTE can start early in life and without any signs of concussion.
A study co-authored by Goldstein and published Thursday in the journal Brain came to that conclusion. It found some changes in the brain occurred as early as 24 hours after injury.
Goldstein and his colleagues advocate for no tackle football before 14 because children's bodies, particularly their necks and upper bodies, aren't strong enough to counteract the bobbling of the head and shaking of the brain that occurs during tackles.
Dr. Julian Bailes, the director of neurosurgery and co-director of NorthShore University HealthSystem Neurological Institute and medical director for Pop Warner, said the concern over repeated hits is magnified in high school, after kids are 14.
"The real exposure to larger players, higher velocity hits and hundreds of hits starts in high school," he said.
Goldstein said parents should heed the warning that CTE can develop early -- and the focus on concussions doesn't reduce the risk.
"The NFL is setting a bad example by focusing on the concussion and while not focusing on the hits," said Goldstein.
The NFL and Dr. Allen Sills, it's chief medical officer, did not respond when asked whether the league is considering changing its CTE and concussion protocol because of the recent study.
"As highlighted in this recent study, repetitive hits to the head have been consistently implicated as a cause of CTE by this research group. How and why exactly this manifests, who is at risk, and why -- these are questions that we as researchers and clinicians are working to answer," Sills said.
Sills noted changes the NFL has made to reduce head-to-head contact over the years, including limiting how much players can wear their helmets off-season and limiting full-padded practices during the season. The NFL has also made grants and supported brain science.
Goldstein said concussions remain the red herring of CTE.
"We will never prevent CTE by focusing on concussions. Any meaningful prevention campaign has to focus on preventing all hits to the head, including sub-concussive impacts," said Goldstein.
And one way to do that, he said, is to limit overall exposure to hits by waiting to play tackle football.
Carson, the former linebacker, noted that "the game is more popular now."
"Parents should understand exactly what they are signing their kids up for," he said.
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