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home : news : news February 26, 2015

2/24/2012 4:38:00 AM
Studies: Repetitive hits cause concussions, long-term brain injuries
But, some experts caution, the science is inconclusive and in its infancy

Richard Moore
Investigative Reporter


Second in a series



There's no question that the number of concussions among players in high-impact sports such as football are on an exponential upcurve, particularly among young players, and the growing numbers have sparked a parallel increase in concussion research.

Not surprisingly, as new research often does, the findings are calling into question traditional approaches to treatment, and beginning to transform thinking about the very nature of the injury. Indeed, if their evidence is confirmed, a trio of papers released in February and last year would stand injury-related neuroscience on its head.

That's because the new research suggests concussions are caused not only by a severe blow to the head or body - a single-hit injury, in other words, the so-called bellringer - but by the repetitive hits an athlete takes during the course of a season and a life. At some point, the new thinking goes, the player passes a threshold where brain injury becomes more likely.

Even more important, the studies indicate, injury becomes more likely both in the short term with concussions and in the long term, potentially leading to degenerative brain disorders such as chronic traumatic encephalopathy (CTE).

Not everyone agrees. Others continue to embrace the traditional approach of safely returning a player to the sport after appropriate concussion management. These experts say the current evidence fails to validate any indication of concussive injury or permanent damage caused by the accumulation of hits over time, and, even if it did, the research is too early to be trusted for policy decisions, at least for now.



The research

The studies are startling nonetheless, whatever the ultimate verdict.

On Feb. 3, Purdue University released an analysis of concussions among high-school football players by the Purdue Neurotrauma Group. Based on brain scans, the researchers determined that concussions "are likely caused by many hits over time and not from a single blow to the head, as commonly believed."

In the study, researchers studied football players for two seasons at Jefferson High School in Lafayette, Ind. During the first season, according to the university, 21 players completed the field test, while 24 completed it in the second season, including 16 repeating players.

Players used helmet sensors, from which researchers compared impact data with brain-imaging scans and cognitive tests performed before, during and after each season, the university stated.

MRI scans of the players found that, as players got hit more and more, brain activity changed, and the players began to adapt their mental processes to deal with those changes. Essentially, the study found, the more impacts, the less functional capacity they had, and players then had to use a different strategy to perform a task at the same level as before.

So while performance might not have noticeably changed, brain activity did, the researchers found. And, the more hits a player took, and the more brain activity change there was, the more likely a concussion was to occur over time, according to the scan results.

"The most important implication of the new findings is the suggestion that a concussion is not just the result of a single blow, but it's really the totality of blows that took place over the season," said one of the researchers, Eric Nauman, an associate professor of mechanical engineering and an expert in central nervous system and musculoskeletal trauma. "The one hit that brought on the concussion is arguably the straw that broke the camel's back."

That calls into question the very assumptions underlying modern concussion management. To be sure, the authors observed, a common assumption in sports medicine is that certain people are innately more susceptible to head injury, but the new findings suggested the number of hits received during the course of a season was the most important factor.

"Most clinicians would say that if you don't have any concussion symptoms you have no problems," Larry Leverenz, an expert in athletic training and a clinical professor of health and kinesiology, said. "However, we are finding that there is actually a lot of change, even when you don't have symptoms."

Former Purdue professor of educational studies Jeffrey Gilger said the findings were particularly critical for the safety of younger people.

"This might be especially important in young people because the brain is still developing, so even though subtle unexpressed damage doesn't manifest as a concussion, it could affect the brain later in life," Gilger said.

Indeed, the study showed that changes were seen in regions of the brain associated with chronic traumatic encephalopathy (CTE), a progressive degenerative disease found in people who suffer numerous concussions and other forms of head injury.

The study is to be published online in the Journal of Biomechanics and was broadly supported in the scientific community, as well as paid for by grants from the Indiana State Department of Health's Spinal Cord and Brain Injury Research Fund, General Electric Healthcare, the Indiana Clinical and Translational Sciences Institute, and through the National Science Foundation and National Defense Science and Engineering Graduate Fellowships.

Some say the study is not to be taken as gospel. Locally, Dr. Bill Melms of the Marshfield Clinic-Minocqua Center sounds a cautionary note. Melms practices in the center's urgent care department, but is also in charge of coordinating concussion management for Lakeland Union High School and Northland Pines through Marshfield Clinic's sports medicine department, and he has recently become LUHS's medical advisor.

"The Purdue study is a paper that's been released," Melms said. "I don't think it's been published in a journal yet. That needs to be published so it can be critically evaluated by those experts in the field. The Purdue study, when you look at it, this is a neuroimaging study, ..., the forefront, kind of the new frontier of concussion research. There were actually only six concussions looked at in that study. It's a small study. We don't know what those brain MRI changes mean."



Michigan data

Melms himself prefers to point to a much larger study conducted by the University of Michigan and Dr. Jeffrey Kutcher.

That study used what is known as a Head Impact Telemetry System in helmets to collect biomechanical data representing over 100,000 head impacts in 95 high school football players over four years. And researchers found no evidence for a cumulative impact effect on concussion injury threshold.

"They analyzed this data to determine if, for instance, one of the thoughts is, in light of the accumulated impact theory, the more hits you get, is there some pattern," Melms said. "If you are getting hit over and over again, is there some change that occurs in your brain that makes it easier for you to get a concussion? That would be a reasonable assumption to make. Well, they determined after analysing this data of 100,000 impacts, that there was no change in concussion threshold. You were just as likely to get a concussion, based on the particular impact, on the first play of the season versus the last play of the season after you have been pounded all season long. And that's objective data, that's hard data looking at 100,000 impacts."

Melms said that made sense to him.

"We certainly had a concussion the first game of the season (locally) this last year," he said. "It's not just accumulation."

And yet, even some of the Michigan researchers, including Kutcher, offered up a caveat.

To be sure, in one paper the researchers wrote that "our data do not support the proposal that impact volume or intensity influence concussion threshold in high school football athletes." That's after the researchers compared the cumulative impact histories prior to 20 concussive impacts in 19 athletes to the cumulative impact histories prior to the three largest magnitude non-concussive head impacts in the same athletes.

Critics of the study point out that the study of 20 concussive impacts is not significantly more than the six analyzed in the Purdue study, and the study also does not assess the accumulation of impacts prior to the four-year period, in younger leagues.

But, more important, the authors themselves wrote a second paper, entitled "Cumulative head impact burden in high school football," and there, using the same data, they raised concerns about the long-term consequences of cumulative hits, even if those impacts did not influence concussion thresholds. In fact, they wrote, the research suggested that consideration should be given to minimizing overall impacts for football players.

"Emerging research has begun to elucidate concussion tolerance levels, but sub-concussive impacts that do not result in clinical signs or symptoms of concussion are much more common, and are speculated to lead to alterations in cerebral structure and function later in life," they wrote. "The adolescent athletes in this study clearly sustained a large number of impacts to the head, with an impressive associated acceleration burden as a direct result of football participation. These findings raise concern about the relationship between sub-concussive head impacts incurred during football participation and late-life cerebral pathogenesis, and justify consideration of ways to best minimize impacts and mitigate cognitive declines."



Cantu wants counts too

Echoing the conclusions of that study, and in fact citing it, is a white paper released Feb. 3 by renowned neurologist Dr. Robert Cantu and former pro wrestler and Harvard football player and graduate Chris Nowinski, the co-founder of the Sports Legacy Institute.

The Sports Legacy Institute has partnerships with, and sponsorships from, a wide array of organizations, including Chicago Public Schools, Morgan Stanley Smith Barney, Brain Injury Association of America, and the Youth Football Coaches Association, among others. Cantu himself is a clinical professor in the Department of Neurosurgery and co-director of the Center for the Study of Traumatic Encephalopathy at the Boston University School of Medicine, as well as a senior advisor to the NFL's Head, Neck and Spine Committee. He is also co-director of the Neurologic Sports Injury Center at Brigham and Women's Hospital and director of sports medicine at Emerson Hospital in Concord, Mass.

The Cantu-Nowinski paper reinforces the Purdue conclusions that multiple hits accumulate and, if too many accumulate over time, could cause serious brain injury.

"Evidence is accumulating that sub-concussive impacts, or impacts that do not produce any clinical concussion symptoms, may still be damaging to the brain, both in the short and long-term," the authors state in the white paper. "One study on high school football players found that players who received normal football brain trauma and did not report any concussion symptoms still had functional MRI changes that mimicked concussion players."

Then, too, they wrote, the evidence connecting brain trauma to CTE, which was first called Punch Drunk in 1928, is older and "more robust" than many believe.

Cantu and Nowinski say that both clinical and pathological studies have established a distinct pathology in the brains of victims of repetitive brain trauma. What's more, they state, everyone diagnosed with CTE upon autopsy - more than a hundred cases - had received such extraordinary brain trauma.

"There are no reported cases of CTE pathology in individuals who did not receive abnormal and excessive repetitive brain trauma," they wrote. "CTE risk appears linked to lifetime brain trauma exposure rather than diagnosed concussions."

The authors used a smoking analogy to make their point, observing that smokers are "only" 15-30 times more likely to develop lung cancer than non-smokers. But, they state, brain trauma victims are far more likely to develop CTE than a smoker is to get lung cancer.

"Brain trauma victims are infinitely more likely to develop CTE, because no one has ever been diagnosed with CTE who was not exposed to that risk factor," they wrote.

In fact, they continued, one older random sample of 250 boxers in the United Kingdom found that 17 percent had indications of CTE using only primitive techniques available at the time, while the Boston University Center for the Study of Traumatic Encephalopathy, in a non-random sample of more than 40 athletes with 10 or more years of experience playing American football, found that over 90 percent of cases were positive for CTE.

Admittedly, Cantu and Nowinski acknowledged, the notion that CTE is linked more to lifetime brain trauma exposure rather than to concussions is tenuous because so many concussions have gone unreported.

"Historically, concussions have not been reported - some estimates indicate fewer than 10% of concussions end up in a medical report - so it is impossible to know any individual's true concussive and sub-concussive history," they wrote.

Nonetheless, they concluded, whether only concussions lead to CTE or subconcussive impacts do as well - or a combination of both - limiting exposure to either or both types of brain trauma would theoretically reduce the long-term risk of CTE.

The bottom line is, they concluded, "the science supports limiting an athlete's lifetime exposure to brain trauma." In lay terms, that means limiting the number of hits a player takes over the course of a season and a lifetime.

That becomes more imperative, Cantu and Nowinski suggest, given the sheer number of high-impact hits football players in America take each season. Their data underscores the University of Michigan review that "adolescent athletes in this study clearly sustained a large number of impacts to the head, with an impressive associated acceleration burden."

Cantu and Nowinski expressed that in absolute numbers. Surveying the available data, they found that football players may receive 2,500 hits to the head exceeding 10 g-forces each season, with the average probably totaling around 1,000 hits per season. The mean hit was found to be around 20 g-forces.

That's a lot of g-forces to take over and over - Apollo 16 astronauts experienced 7.19 g-forces upon their re-entry to the Earth, for instance - and it is a particularly important consideration for younger athletes, the authors observed.

"The fact that the data indicates youth athletes are exposed to brain trauma with high frequency and severity is concerning, as most experts agree that the young brain is more vulnerable to trauma than the mature brain," Cantu and Nowinski wrote. "The young athlete is at biomechanical disadvantages as well, as their head reaches 90% of full size by age 5, yet their body is only 20% of adult mass."

Younger players also lack many of the resources and skills possessed by more mature older players.

"Young athletes also have an absence of medical resources to help identify when a concussion has occurred," they wrote. "Among many other disadvantages, studies show children lack the knowledge and verbal skills to report concussion symptoms to adults."

So where does all this leave contact sports, especially football, when it comes to younger players, namely, those under the age of 14?

The range of opinions is as wide and varying as the research, from those saying sound concussion management is good enough, to those advocating new training protocols for younger players, to those who want to establish so-called "hit counts" for players, to those who want to ban the contact version of the sport altogether.

That discussion is next.

Richard Moore may be reached at richardmoore.gov@gmail.com

Related Stories:
• Reducing hit counts may help reduce concussions
• Concussion scrutiny sweeps the world of sports
• Movement grows to minimize hits for young football players
• Sports concussions grow, and so does the controversy



Reader Comments

Posted: Tuesday, February 28, 2012
Article comment by: gary bohlin

In our town Elgin il. our local paper just ran a front page article promoting the park and rec. taxpayer subsidized childrens boxing program! Talk about a knockout!

Posted: Friday, February 24, 2012
Article comment by: Dr. C. J Abraham

The totality of blows is important. However, counting blows does not make sense. Since impacts to the brain are cumulative, a count will make sense if every impact is identical which we know is impossible to occur.The development of the brain and the strength of the neck varies with each young player.

By being pro-active, the number of head injuries in the sport of soccer can be significantly reduced.




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