Former pro football player Kevin Turner, shown here during a 1998 NFL game,<strong> </strong><a target="_blank">had the most advanced stage of CTE</a> when he died in March at the age of 46. Dr. Ann McKee of Boston University and the Concussion Legacy Foundation said that Turner's CTE brought on amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease. <br /><br />CTE stands for chronic traumatic encephalopathy, a neurodegenerative disease associated with repeated head trauma. Scientists believe repeated head trauma can cause CTE, a progressive degenerative disease of the brain. Symptoms include depression, aggression and disorientation, but scientists can definitively diagnose it only after death.
Former pro football player Kevin Turner, shown here during a 1998 NFL game, had the most advanced stage of CTE when he died in March at the age of 46. Dr. Ann McKee of Boston University and the Concussion Legacy Foundation said that Turner's CTE brought on amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease.

CTE stands for chronic traumatic encephalopathy, a neurodegenerative disease associated with repeated head trauma. Scientists believe repeated head trauma can cause CTE, a progressive degenerative disease of the brain. Symptoms include depression, aggression and disorientation, but scientists can definitively diagnose it only after death.
Getty Images
BMX star Dave Mirra, who was found dead of a self-inflicted gunshot in February, <a target="_blank">was found to have CTE. </a>
BMX star Dave Mirra, who was found dead of a self-inflicted gunshot in February, was found to have CTE.
Christian Petersen/Getty Images
<a href="https://www.chinalucky8.com/2011/SPORT/08/03/bubba.smith.obit/">Charles "Bubba" Smith</a>, a former football player and actor who died in 2011, was also diagnosed with CTE. Smith played for the Baltimore Colts, the Oakland Raiders and the Houston Oilers.
Charles "Bubba" Smith, a former football player and actor who died in 2011, was also diagnosed with CTE. Smith played for the Baltimore Colts, the Oakland Raiders and the Houston Oilers.
Tony Tomsic/Getty Images
Former Minnesota Vikings linebacker Fred McNeill died in November 2015 due to complications from ALS. However, an autopsy confirmed that he suffered from CTE. What makes <a target="_blank">McNeill's case</a> even more remarkable, though, is that he was potentially the first to be diagnosed while alive. Doctors used an experimental new technology to examine his brain.
Former Minnesota Vikings linebacker Fred McNeill died in November 2015 due to complications from ALS. However, an autopsy confirmed that he suffered from CTE. What makes McNeill's case even more remarkable, though, is that he was potentially the first to be diagnosed while alive. Doctors used an experimental new technology to examine his brain.
Courtsy McNeill Family
Oakland Raiders quarterback Ken Stabler, a former NFL MVP who died in July 2015, <a target="_blank">suffered from CTE,</a> researchers at Boston University said.
Oakland Raiders quarterback Ken Stabler, a former NFL MVP who died in July 2015, suffered from CTE, researchers at Boston University said.
Robert Riger/Getty Images
Kansas City Chiefs linebacker Jovan Belcher shot and killed his girlfriend before killing himself in December 2012. <a target="_blank">Pathology reports</a> show he probably had CTE.
Kansas City Chiefs linebacker Jovan Belcher shot and killed his girlfriend before killing himself in December 2012. Pathology reports show he probably had CTE.
Jamie Squire/Getty Images
Hall of Fame offensive lineman Mike Webster was the first former NFL player to be diagnosed with CTE. After his retirement, Webster suffered from amnesia, dementia, depression, and bone and muscle pain.
Hall of Fame offensive lineman Mike Webster was the first former NFL player to be diagnosed with CTE. After his retirement, Webster suffered from amnesia, dementia, depression, and bone and muscle pain.
George Gojkovich/Getty Images
The death of 36-year-old Pittsburgh Steelers offensive lineman Justin Strzelczyk put the link between football and CTE in the national spotlight. Strzelczyk was <a target="_blank" target="_blank">killed in a 2004 car crash</a> crash after a 40-mile high-speed chase with police in New York.
The death of 36-year-old Pittsburgh Steelers offensive lineman Justin Strzelczyk put the link between football and CTE in the national spotlight. Strzelczyk was killed in a 2004 car crash crash after a 40-mile high-speed chase with police in New York.
George Gojkovich/Getty Images
Evidence of CTE was found in the brain of football player Lew Carpenter after his death in 2010 at the age of 78.
Evidence of CTE was found in the brain of football player Lew Carpenter after his death in 2010 at the age of 78.
Henry Barr Collection/Diamond Images/Getty Images
Pro Football Hall of Famer Louis Creekmur, who played for the Detroit Lions from 1950 to 1959, suffered decades of cognitive decline before his death.
Pro Football Hall of Famer Louis Creekmur, who played for the Detroit Lions from 1950 to 1959, suffered decades of cognitive decline before his death.
Bob D'Olivo/Source Interlink Media/Getty Images
Linebacker John Grimsley of the Houston Oilers died of an accidental gunshot wound to the chest in 2008. Analysis of his brain tissue confirmed damage to the neurofibrillary tangles that had begun to affect his behavior and memory.
Linebacker John Grimsley of the Houston Oilers died of an accidental gunshot wound to the chest in 2008. Analysis of his brain tissue confirmed damage to the neurofibrillary tangles that had begun to affect his behavior and memory.
George Gojkovich/Getty Images
Chris Henry played five seasons for the Cincinnati Bengals before dying at the age of 26. <a target="_blank">He died after falling from the bed of a moving pickup</a> during a fight with his fiancée. His young age prompted concern over how quickly athletes start to suffer from CTE.
Chris Henry played five seasons for the Cincinnati Bengals before dying at the age of 26. He died after falling from the bed of a moving pickup during a fight with his fiancée. His young age prompted concern over how quickly athletes start to suffer from CTE.
Joe Robbins/Getty Images
Offensive lineman Terry Long of the Pittsburgh Steelers committed suicide by drinking antifreeze. Although the antifreeze caused swelling of the brain, football-related brain injuries were a contributing factor to his death.
Offensive lineman Terry Long of the Pittsburgh Steelers committed suicide by drinking antifreeze. Although the antifreeze caused swelling of the brain, football-related brain injuries were a contributing factor to his death.
George Gojkovich/Getty Images
Pro Football Hall of Famer John Mackey suffered from dementia for years before dying at the age of 69.
Pro Football Hall of Famer John Mackey suffered from dementia for years before dying at the age of 69.
Richard Stagg/Getty Images
Ollie Matson, who played 14 NFL seasons starting in the 1950s, suffered from dementia until his death in 2011.
Ollie Matson, who played 14 NFL seasons starting in the 1950s, suffered from dementia until his death in 2011.
SN Archive/Getty
Andre Waters spent most of his 12 seasons with the Philadelphia Eagles before his suicide at age 44.
Andre Waters spent most of his 12 seasons with the Philadelphia Eagles before his suicide at age 44.
George Gojkovich/Getty Images
Tom McHale of the Tampa Bay Buccaneers, right, died in 2008 <a >of an apparent drug overdose</a> at the age of 45.
Tom McHale of the Tampa Bay Buccaneers, right, died in 2008 of an apparent drug overdose at the age of 45.
Focus on Sport/Getty Images
Junior Seau <a >took his own life</a> in 2012 at the age of 43. The question of CTE came up immediately after his death; scientists at the National Institutes of Health confirmed the diagnosis in January 2013.
Junior Seau took his own life in 2012 at the age of 43. The question of CTE came up immediately after his death; scientists at the National Institutes of Health confirmed the diagnosis in January 2013.
Al Bello/Getty Images
Pro wrestler Chris Benoit was found dead at his suburban Atlanta home along with his wife, Nancy, and son in an apparent murder-suicide. Testing found that the damage to his brain was similar to that of an elderly Alzheimer's patient.
Pro wrestler Chris Benoit was found dead at his suburban Atlanta home along with his wife, Nancy, and son in an apparent murder-suicide. Testing found that the damage to his brain was similar to that of an elderly Alzheimer's patient.
Darryl Dyck/Edmonton Sun/AP
Reggie Fleming, who played for six NHL teams, was the first hockey player to be diagnosed with CTE.
Reggie Fleming, who played for six NHL teams, was the first hockey player to be diagnosed with CTE.
New York Rangers/AP
Hockey player Bob Probert was found to have CTE after dying of heart failure at the age of 45.
Hockey player Bob Probert was found to have CTE after dying of heart failure at the age of 45.
B Bennett/Getty Images
<a >Ryan Freel </a>became the first Major League Baseball player to be diagnosed with CTE nearly a year after he committed suicide at age 36.
Ryan Freel became the first Major League Baseball player to be diagnosed with CTE nearly a year after he committed suicide at age 36.
Chris McGrath/Getty Images
Athletes and CTE

Story highlights

Former football players are supporting new education initiative, Flag Football Under 14

"Please don't let your children play football until high school," one Hall of Fame player said

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.

brain differences
Allie Schmitz / CNN

Related article It's not concussions that cause CTE. It's repeated hits, a study finds

“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.

Family photos of former Minnesota Vikings football player Fred McNeill.
Family photos of former Minnesota Vikings football player Fred McNeill.
Courtsy McNeill Family

Related article Ex-NFL player confirmed as 1st case of CTE in living patient

“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.

you football stat 02

Related article Would you let your child play football?

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.

American Football Helmet on the Field with room for copy; Shutterstock ID 152570240
American Football Helmet on the Field with room for copy; Shutterstock ID 152570240
David Lee/Shutterstock

Related article CTE found in 99% of studied brains from deceased NFL players

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.

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    “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.

    CNN’s Kwegyirba Croffie contributed to this report.