The Dangers of Repeat Concussion

In our last two posts we talked about how common concussions are.  Unfortunately repeat concussion are also quite common.  In his landmark study of concussions in NCAA football players Kevin Guskiewicz reported that 6.5% of players reported repeat concussions within the same season.  The NFL’s own data from its suspect Mild Traumatic Brain Injury (MTBI) Committee reported a 24.5% rate of repeat concussions over the 5-year period from 1996-2001 during which they collected their data. Once again, though, we see the problem with underreporting of concussions.  In 2005 Guskiewicz surveyed 2552 retired players of the NFL Retired Players Association.  24% reported 3 or more concussions during their careers.  A similar anonymous mail survey of high school football players in Ohio and Pennsylvania found a rate of repeat concussion of nearly 35% (Langburt et al, 2001).  So clearly we see that reported rates of concussion are higher when the queries are anonymous and the player isn’t afraid of missing out on playing time.

What does it matter if repeat concussions are common?  First, concussions beget more concussions.  In Guskiewicz’s NCAA study, players with 3 or more concussions were 3 times more likely to get subsequent concussions.  These repeat concussions were most likely to occur in the first 7 days after the initial concussions.   Players with repeat concussion are also more likely to have more severe injuries with each concussion.  In 2002 Micky Collins et al looked at the effects of repeat concussions in 173 high school athletes (most but not all were football players.)  They found that players with 3 or more concussions were 9 times more likely to have several of the “severe” symptoms in the study such as amnesia, loss of consciousness and confusion.  It’s clear from these and other data that concussions increase the brain’s vulnerability to injury and that the severity of this injury becomes more severe with repeat concussions.

In some cases injury after repeat concussion can be quite dramatic.  The North Carolina version of Zach’s Law is called the Gfeller-Waller Concussion Awareness Act.  In 2009 Jaquan Waller, a junior at Greenville Rose High School in Greenville, NC, sustained a concussion during football practice.  A few days later he was hit again in the head during a game and died of what likely was second impact syndrome (SIS).  In this rare phenomenon a player sustains a concussion and within days, and in some cases even weeks, sustains a second concussion while he’s still symptomatic from the first.  The second concussion results in an extreme response in the brain that is usually fatal.  It’s thought that this response involves impaired regulation of blood flow in the brain which results in a massive increase in pressure in the brain which then results in coma and death.  Thankfully SIS is quite rare.

The delayed injuries that result from repeat concussions are not as dramatic as SIS but are every bit as scary.  It’s clear from recent evidence that multiple concussions seem to cause serious delayed physical, psychological and cognitive pathology in some players years and even decades after they stop playing sports.  The 2005 survey of retired NFL players showed that players who sustained 3 or more concussions were much more likely to develop memory problems and cognitive impairment.  Also, players who sustained multiple concussions developed Alzheimer’s disease (AD) at an earlier age than the average male (although the study found no causative link between multiple concussions and AD.)  This and multiple subsequent studies have clearly shown that there is real, long-term cognitive and behavioral impairment that results from repeat concussions in sport.

What causes the long-term impairment in some players who sustain multiple concussions during their playing days?  Early evidence of true, organic brain damage after repetitive head injury came from the study of boxers.  The term “punch drunk syndrome”, later referred to as dementia pugilistica (DP), was first used by Dr. Harrison Stanford Martland in 1928 to describe the clinical findings of tremors, memory loss, speech difficulties and confusion seen in some boxers late in their careers.  In 1973 Corsellis looked at the brains of 15 deceased boxers with DP and discovered deposits of abnormal tau proteins scattered throughout the brains (similar to those found in AD but in different locations within the brain).  Here, for the first time, was microscopic evidence of the damage that occurs in the brains of boxers after careers marked by repetitive blows to the head.  It’s now thought that with repetitive head trauma, microglia, the brain’s immune cells, become abnormally activated and then wreak havoc on the cellular architecture of the brain leaving abnormal tau protein tangles in their wake.

Today, DP is known as chronic traumatic encephalopathy, or CTE.  CTE was first described in a professional football player by Dr. Bennet Omalu, a Nigerian pathologist in the Allegheny County, PA coroner’s office, who performed the post-mortem brain examination on hall-of-fame Pittsburgh Steelers center Mike Webster.  After his retirement from the NFL in 1990 Webster suffered a highly-publicized descent into madness.  Omalu wondered if Webster’s psychological and cognitive decline could be caused by the same brain damage seen in Corsellis’ deceased boxers.  Despite the fact that Webster died of a heart attack Omalu pushed to have his brain harvested and was able to diagnose CTE.  This diagnosis, for the first time, provided a link between the concussions sustained in professional football and long term brain damage in a retired player.  In my opinion this was a pivotal moment in American sports history. (Watch a fascinating interview with Dr. Omalu about his discovery here.)   Not unsurprisingly, the NFL vehemently denied the validity of Omalu’s discovery (watch Ira Casson, then head of the NFL’s MTBI committee, below), even calling for the retraction from the publication of the Webster case from the journal Neurosurgery.   Unfortunately for the NFL, though, the discovery of CTE after the suicides of players like Terry Long, Andre Waters, Justin Strzelczyk and Junior Seau ultimately made it a lot more difficult to deny the dangers of repeat concussion in the NFL.  CTE has now been found in the brains of dozens of retired NFL players and is the lynchpin of the NFL’s $1 billion settlement with former players.  As more and more cases of CTE are discovered in the brains of disabled retired players, it may become apparent that the NFL got off easy (especially when you consider the $10 billion in revenues the NFL brings in annually.)  I could go on and on about the NFL’s shameful response to its concussion crisis but I won’t.  If you’re interested in reading more about this topic a fascinating read is League of Denial by ESPN writers Mark Fainaru-Wada and Steve Fainaru.  The sister documentary on PBS Frontline is also outstanding.

Perhaps the scariest thing is that blows to the head that aren’t severe enough to cause concussions, so called subconcussive hits, can also cause CTE.  An autopsy study by Bailes et al in 2013 looked at the brains of 8 NFL players who had never had a concussion.  All of them had CTE.  It’s now believed that routine hits, even the hits sustained in practice, if repetitive, can lead to the same long-term damage as repetitive concussions.  Why is that scary?  Consider the study done by Cobb et al which looked at HITS telemetry data in Pop Warner football players 9-12 years of age (also consider that 4.5 million kids play Pop Warner football each season.)  The players in the study sustained an average of 240 blows to the head a season!  While most hits were below 45g in magnitude some players sustained hits above 80g (remember that the NFL defined a concussion threshold at 75g).  Granted, not all players who sustain repetitive hits to the head develop CTE (and researchers are still trying to determine why.)  One has to ask, though, now that we know the risks involved, is it worth it to let our children play sports that put them at risk of repetitive head injury?

Thanks for reading.

J. Alex Thomas, M.D.


Bailes, J., Petraglia, A., & Omalu, B. (2013). Role of subconcussion in repetitive mild traumatic brain injury: A review. Journal of …, 119(November), 1235–1245.

Cobb, B. R., Urban, J. E., Davenport, E. M., Rowson, S., Duma, S. M., Maldjian, J., Stitzel, J. D. (2013). Head impact exposure in youth football: Elementary school ages 9-12 years and the effect of practice structure. Annals of Biomedical Engineering, 41(12), 2463–2473.

Collins, M. W., Lovell, M. R., Iverson, G. L., Cantu, R. C., Maroon, J. C., & Field, M. (2002). Cumulative effects of concussion in high school athletes. Neurosurgery, 51(5), 1175–1181.

Guskiewicz, K. M., Mccrea, M., Marshall, S. W., Cantu, R. C., Randolph, C., Barr, W., Kelly, J. P. (2003). Cumulative Effects Associated With Recurrent Concussion in Collegiate Football Players: The NCAA Concussion Study. JAMA, 290(19), 2549–2555.

Guskiewicz, K. M., Marshall, S. W., Bailes, J., McCrea, M., Cantu, R. C., Randolph, C., & Jordan, B. D. (2005). Association between recurrent concussion and late-life cognitive impairment in retired professional football players. Neurosurgery, 57(4), 719–726; discussion 719–726.

Langburt, W., Cohen, B., Akhthar, N., O’Neill, K., & Lee, J. C. (2001). Incidence of concussion in high school football players of Ohio and Pennsylvania. Journal of Child Neurology, 16, 83–85.

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