FRIDAY, March 20, 2015 (HealthDay News) -- Medical science has shown that football can take a terrible toll on the human brain, with repeated hits to the head potentially adding up to brain damage later in life.
But, it's been unclear whether players actively consider and accept the risk of brain injury as the price to be paid for their often-lucrative participation in America's most popular sport.
The surprising retirement Monday of National Football League standout rookie linebacker Chris Borland shows that some players are indeed weighing that risk, and coming to the conclusion that it's just not worth it.
Borland's announcement caps a tumultuous decade for football, in which the science of concussion-related brain injury has placed the sport in a light that's become more and more damning.
A number of former NFL players report struggling with thinking, memory and emotional problems, and autopsies of football players have revealed brains riddled with atrophy and abnormalities. Research has linked concussions -- particularly repeated concussions -- to increased risk of dementia, depression and other forms of mental impairment, according to the U.S. Centers for Disease Control and Prevention.
Even hits to the head that don't result in concussion are now being weighed as a potential source of brain injury, said Jay Alberts, director of the Cleveland Clinic's Concussion Center.
Scientists are increasingly concerned that brain damage might accumulate from the thousands of "sub-concussive" hits that a player absorbs during his career, stretching back through college, high school and youth league days, Alberts said.
"It's probably those sub-concussive blows that we really need to be understanding and worrying about," he said. "That's something they're experiencing often."
It's in this atmosphere that the 24-year-old Borland announced his decision to retire after a stellar rookie season in which he led the San Francisco 49ers in tackles.
Having suffered two diagnosed concussions, he specifically cited concerns about brain trauma as his reason for walking away from a promising career and piles of cash.
"I just thought to myself, 'What am I doing? Is this how I'm going to live my adult life, banging my head, especially with what I've learned and knew about the dangers?'" Borland told ESPN.
The NFL released a statement respectfully accepting Borland's decision, but also touting its efforts to make football a safer game for players.
"By any measure, football has never been safer and we continue to make progress with rule changes, safer tackling techniques at all levels of football, and better equipment, protocols and medical care for players," Jeff Miller, the NFL's senior vice president of health and safety policy, said Tuesday in a prepared statement.
"Concussions in NFL games were down 25 percent last year, continuing a three-year downward trend," Miller said. "We continue to make significant investments in independent research to advance the science and understanding of these issues. We are seeing a growing culture of safety. Everyone involved in the game knows that there is more work to do and player safety will continue to be our top priority."
Health risks prompting self-examination by players
Despite the NFL's efforts, there's a lot of soul-searching going on now among the league's players, noted sports agent Leigh Steinberg said.
Players with other career options -- those with good college degrees or financially secure families -- might turn away from football because of the threat to their mental health, he said.
"There's no question but that this [Borland] retirement sparks conversation and introspection on the part of some group of players in the NFL," said Steinberg, who was among the group of people to first draw attention to football's concussion crisis. "Some are caught too deeply in denial and some need to gain too much, but players who can envision other second careers are going to start to think about this."
Borland is the poster child for those players with options. "Here's someone with a college degree from reasonably affluent circumstances who can envision a career beyond football, and he has that choice," Steinberg said.
Pro football's concussion crisis began anecdotally, with reports of individual players suffering severe mental and emotional disabilities after retiring from the NFL.
Legendary Pittsburgh Steelers center "Iron Mike" Webster endured perhaps the most public decline. Following his retirement in 1990, Webster struggled with a mental deterioration that left him jobless, homeless and divorced.
Webster reportedly died of a heart attack in 2002, at age 50, and inadvertently became the foundation for what is now known about football-related brain injury.
A forensic pathologist in Pittsburgh, Dr. Bennet Omalu, examined Webster's brain and found damage reminiscent of that suffered by people with advanced Alzheimer's disease.
Omalu ended up diagnosing Webster with chronic traumatic encephalopathy (CTE), a term he helped coin to describe the progressive degenerative neurological damage apparently caused by repeated trauma to the brain.
Symptoms of brain damage can take decades to surface
People with CTE tend to experience a decline in their short-term memory and find it difficult to organize and plan, according to the CDC.
They also exhibit emotional problems -- depression, impulsivity, aggressiveness, anger, irritability, suicidal behavior and eventual dementia. The symptoms typically do not manifest themselves until decades after the trauma that prompted them.
Since Webster's death in 2002, more NFL players have come forward to say they have been experiencing symptoms of CTE.
"I signed up for this when, I guess, I started playing football so many years ago. But, obviously, not knowing that the end was going to be like this," said Dallas Cowboys Hall of Fame running back Tony Dorsett, who's now 60. "But I love the game. The game was good to me. It's just unfortunate that I'm going through what I'm going through."
In pain and confusion, some players suffering mental decline have even opted for death.
Former Chicago Bears defensive back Dave Duerson took his own life in 2011 at age 50 with a gunshot wound to the chest, reportedly so his brain could be examined for signs of CTE.
Junior Seau, a former star linebacker for the San Diego Chargers, killed himself in exactly the same way in 2012.
Post-mortem examinations revealed that both men had suffered from CTE.
Researchers at the Boston University CTE Center have found that 76 out of 79 brains from deceased former NFL players have shown signs of chronic traumatic encephalopathy, said Dr. Robert Cantu, a professor of neurosurgery at the BU School of Medicine and an investigator for the center.
Damage can start long before the pro football level
Brain damage due to football-related concussion isn't limited to the NFL, researchers have found.
"We've seen CTE as young as in four high school players who had it, and we've seen it in a number of college players," Cantu said. "You don't have to be in the NFL to develop CTE."
Repetitive head injury results in structural and functional changes in the brain, Alberts said, and the damage appears to stack up on itself. For example, people who sustain a concussion while still recovering from an earlier one appear to be at even greater risk.
"Leading neurologists tell us that three or more concussions occasion an exponentially higher rate of ALS [Lou Gehrig's disease], Alzheimer's, premature senility, chronic traumatic encephalopathy and depression," Steinberg said.
NFL player data submitted as part of a class-action concussion lawsuit against the league indicate that nearly 30 percent of former players will end up developing Alzheimer's or dementia, according to Forbes magazine.
An actuarial firm hired by the players estimated that about 14 percent will be diagnosed with Alzheimer's, and another 14 percent will develop moderate dementia. That stands at about twice the risk faced by the general population, the firm concluded.
The lawsuit is close to final federal approval.
The agreed-upon settlement would provide financial compensation and neurological care for about 25,000 former NFL players who develop conditions such as Lou Gehrig's disease, CTE, Alzheimer's or Parkinson's, according to USA Today. In the settlement, the NFL would make no admission of guilt and ex-players would not have to prove their conditions are related to NFL football.
Not all players suffer traumatic consequences
Researchers now are looking into the effect of jarring hits to the head that don't cause concussion, Steinberg and Alberts said.
"They now believe that every time an offensive lineman hits a defensive lineman at the inception of every football play, it produces a low-level sub-concussive event," Steinberg said. "An offensive lineman can walk out of football with 10,000 sub-concussive hits, none of which have been diagnosed, none of which he's aware of, but the aggregate of which almost certainly does worse brain damage than three knockout blows."
Said the Cleveland Clinic's Alberts: "If you're a linebacker, sub-concussive hits are more frequent than concussive hits. Just because you haven't crossed over the threshold into an official concussion doesn't mean those hits to the head are negligible or don't have any effect on function."
However, researchers also have found that there's no way to tell which players ultimately will suffer from CTE. Some former players are fine even after experiencing years of blows, experts said.
Troy Aikman and Steve Young were both Hall of Fame quarterbacks in the 1980s and '90s who retired after a series of concussions. Yet both are now equally successful pro football analysts on TV.
"Unfortunately, we cannot wisely counsel young people in terms of what is their risk, because we don't know it," said Boston University's Cantu. "We just know the longer you play and the more hits you take, the greater risk you have for developing CTE if you are susceptible to CTE."
Researchers would like to figure out the genetics behind susceptibility to CTE, to give players a better idea of their risk, Alberts said.
They also are investigating ways to track a player's "impact dose" for each hit, as well as a biological or blood test that would give players and their physicians an early indication of the brain damage they have sustained following a year's worth of play.
"It could be a function of frequency and exposure," Alberts said. "It's sort of like asbestos. If you're continually exposed to it, you're certainly at increased risk of cancer compared to if you walk through an old classroom with an exposed pipe."
Many players, fans back Borland's decision to retire at 24
This growing stack of medical evidence has created a crisis of conscience for some football players, as well as those who love and support them.
Borland's early retirement is the most recent evidence of that ongoing crisis.
"It's a dramatic marker in the evolution of concussion awareness among players in the NFL," Steinberg said. "Here you have a player about to embark on a career with the San Francisco 49ers, which will lead him to massive riches and prestige, and he turns away because of the risk of brain damage."
Observers found as striking the reaction of fans and fellow players, many of whom supported Borland's decision.
"WOW. I loved Chris Borland's game but I can't fault him for calling it quits. His concerns are real. Still it takes a man to do the logical," St. Louis Rams defensive end Chris Long, son of Hall of Fame defensive end Howie Long, said on Twitter. "I don't feel bad for Borland. I feel happy for him. He's made a tough choice."
"Shocked to hear the news about my dude Borland, but I totally understand his decision to retire #muchrespect," tweeted linebacker Chase Thomas, a teammate of Borland's on the 49ers.
Both Borland's decision and the reception it received run counter to the macho, play-through-pain image associated with the NFL and embraced by its fans for decades.
"I've had football players, one play with a collapsed lung, another with broken ribs, another with a broken leg," Steinberg said. "They're brave and courageous, but they take risks that don't fit anyone's standards of protecting health."
Efforts under way to make the game safer, for kids up to pros
In response to the growing awareness of the dangers of football, steps are being taken to make the game safer for all players, from Pop Warner kids up to NFL pros.
Cantu said he and other experts have recommended that only flag football, with no tackling, be allowed for kids younger than 14, due to the effect concussions can have on a brain that's still developing.
In addition, a number of states have recommended mandates that limit the amount of contact that high school players can face. Players don't tackle during training camp, and go through only limited tackling during a week's practice, to remove as much contact as possible.
At the NFL level, teams have brought in neurologists and concussion experts to examine players and to train staff to recognize the signs of concussion. Teams are being urged to keep players off the field until their concussions have healed completely, and then ease them back into play.
Players are being taught better blocking and tackling techniques, so they stop using their heads as weapons. And medical experts are developing better diagnostic techniques to identify concussions on the sideline, Steinberg said.
But football ultimately is a violent game, and there's ongoing debate about how safe it can ever truly be.
"We have players with extraordinary size, speed and strength," Steinberg said of the NFL. "The physics of the hit have changed. The game can't be safer than ever when you have a 375-pound offensive lineman able to run a five-flat forty [40 yards in 5 seconds]. They've measured the actual G-forces at the line of scrimmage and it's exponentially higher than it was 20 years ago."
Lee Igel is a clinical associate professor at the Tisch Institute for Sports Management Media and Business at the NYU School of Professional Studies. "It's tough to get away from the fact that this is a contact sport, and it's one of the concerns that players seem to have," he said. "This is the game we play, and if you take too much out of it, that changes the game and it's not football anymore. That's the tough nut to crack."
Will football follow a path similar to that of boxing?
If football can't be made much safer, who will choose to play it in the future?
"Not my son," many American parents seem to be saying.
Half of Americans don't want their sons playing football, according to a recent Bloomberg Politics poll. Another survey, by Robert Morris University, found that nearly half of parents interviewed believe boys shouldn't be allowed to play tackle football until they reach high school.
Even football insiders are having second thoughts. Hall of Fame player and coach Mike Ditka, leader of the tough-as-nails 1985 Chicago Bears, told Bryant Gumbel on HBO's Real Sports that he wouldn't want an 8-year-old boy playing football.
"Nope, and that's sad," Ditka said. "I wouldn't. My whole life was football. I think the risk is worse than the reward. I really do."
Steinberg, Cantu and Igel all predict that football will survive, but that the makeup of those playing the game will change in coming years.
They say football's likely to go the way of boxing, where people with financial security and good educations stop participating.
Boxing historically has served as a means of getting ahead for members of ethnic groups on society's lower rungs, Steinberg said -- the Irish, Jews, Italians, blacks, Hispanics. "As each group became more successful and more well-integrated, those kids stopped boxing," he said.
Igel said of football: "Give it enough time and you come closer and closer to the point where it's left to people who want some level of upward mobility. They're poor. This is a way to earn some money. And at the end of the day, people of means will probably not be playing this sport."
If football starts to be seen as a brutal pastime that chews up players coming from hard-luck circumstances with limited options, that could slowly erode the sport's popularity, Igel suggested.
"It's a real business concern for the NFL, and a social concern for the NFL and the rest of us," he said.
Or as Steinberg put it, speaking of his own "crisis of conscience" regarding concussions and pro football: "It's a traumatizing thing to think you may enrich someone's bank book by facilitating their involvement in something that may cause them brain damage."
For more on complications from concussions, visit the U.S. Centers for Disease Control and Prevention.