How common is CTE? What we can learn from research on former NFL players

Boston University has found Chronic Traumatic Encephalopathy (CTE), a degenerative brain disease that has been linked to repetitive brain injuries, in the brains of 345 out of 376, or 92%, of former NFL players studied. While this is a striking and concerning number, it does not mean that 92% of all former NFL players have this disease. Let’s put this finding in context and discuss what it means for all contact sport athletes today.

What is CTE?

CTE is a degenerative brain disease that has been linked to exposure to repetitive brain trauma. That brain trauma can include both concussions and repetitive “subconcussive” impacts. The disease has been diagnosed in some individuals with no documented concussions but a history of repetitive head impacts that do not result in symptoms. Those repetitive impacts can occur on every play in many sports, including every tackle or collision between linemen in football, every check in hockey, and every header in soccer.

CTE has been diagnosed in individuals with a variety of exposure to repetitive brain trauma, including football, soccer, hockey, and rugby athletes, as well as military veterans and victims of domestic violence. CTE symptoms often begin in middle-age, sometimes years after the last exposure to brain trauma, and can include cognitive difficulties, memory loss, behavioral difficulties, impulsivity, and depression, among other symptoms.

At this time CTE cannot be diagnosed during life. It can only be diagnosed by postmortem examination of the brain. Generous donors and their families have donated their brain to brain banks studying the disease, such as the Boston University/Concussion Legacy Foundation Brain Bank, after they pass away. This incredibly gift from donors has lead to breakthroughs in research about the long-term consequences of repetitive brain trauma in sports, the military, and beyond.

Do 92% of NFL players have CTE?

The answer is almost certainly “no.” Brain banks have a selection bias. The sample they study is not random. Most players or their families don't think to donate their or their loved one's brain unless they think they have the disease. As a result, it is not surprising that many of the donors had CTE.

It is highly unlikely that ever other former NFL player that passed away during the same time period as those studied at Boston University had CTE. Thus, it is unlikely that 92% of all NFL players have the disease.

Despite the bias, the prevalence of CTE in NFL players is still likely high. After previous research showed 110 of 111 former NFLers examined had CTE, a study found that, if it is assumed that all other players who passed away in the same time period did NOT have CTE, the minimum prevalence rate would be 9.6%. That is about one in ten players, or about 5 players on every active NFL roster.

It is highly likely that some of the former players who passed away but were not studied did have CTE but were not diagnosed, making that prevalence even higher.

What does this mean for most current or former contact sport athletes?

We don’t know the true prevalence of CTE in the NFL population or in any contact sport athletes at any level. There is evidence that the risk for developing CTE increases with a greater number of repetitive head impacts over a lifetime. In one study, those who played tackle football for 14 years or more were ten times more likely to develop CTE, while those who played tackle football for 4 years or less were ten times less likely to develop the disease.

Still, there are cases of athletes who played contact sports only through the high school level that developed CTE. The youngest documented case I am aware of was in a 17-year-old. While the prevalence at this level is likely low, there is still risk.

For those who are concerned that they may have CTE based on their athletic history and current symptoms, CTE symptoms are not unique to CTE. Depression, certain cognitive difficulties, and anxiety, for example, can have many causes, and these symptoms can be treated.

As Dr. Ann McKee said in a Boston.com article:

“While the most tragic outcomes in individuals with CTE grab headlines, we want to remind people at risk for CTE that those experiences are in the minority,” Ann McKee, director of the BU CTE Center and chief of neuropathology at VA Boston Healthcare System, said in a statement. “Your symptoms, whether or not they are related to CTE, likely can be treated, and you should seek medical care. Our clinical team has had success treating former football players with mid-life mental health and other symptoms.”

If you are concerned that you or a loved one may have symptoms that may be related to CTE or previous concussions, you can contact the Concussion Legacy Foundation HelpLine. The Concussion Legacy Foundation has many resources available about CTE, Concussions, and Post-concussion syndrome. The HelpLine can provide referrals, online support groups, one-on-one peer support, and other resources.

New Research Review: Can a saliva test diagnose a concussion?

A new study conducted by researchers at the University of Birmingham in the U. K. has found that biomarkers in saliva may be useful for diagnosing a concussion. Concussions can currently only be diagnosed based on symptoms and clinical evaluation, and it is common for athletes to hide their symptoms so they can continue to play. An objective test that could quickly and easily diagnose concussions would be a game changer. This has been covered widely in the media, with some headlines reading “New Saliva Test Can Quickly Diagnose Concussions.” But are the headlines accurate? What does this mean for athletes playing sports today?

What did the study find?

The study was conducted in male professional rugby players in England across two seasons of play. All athletes gave saliva samples before the season started as a baseline. Then those who were assessed for a head injury in a game provided saliva samples during the in-game evaluation, immediately after the game, and 36 to 48 hours post-game. Uninjured players who played in the same game and players who were removed from the game due to a musculoskeletal injury also provided saliva samples at the post-game time points.

This study design allowed for a comparison to each athlete’s own baseline sample as well as between concussed athletes, those who were assessed but determined not to have a concussion, and other athletes who played in the game. That is an important strength of the study. Repetitive head impacts have been shown to cause changes in the brain over the course of a season and even a single game. The researchers needed to determine if the concussion caused saliva changes above and beyond the repetitive impacts. Concussions were diagnosed in 106 players in the study, while 50 players were assessed but determined not to have a concussion.

The saliva was examined for molecules called microRNAs. Previous research has suggested that different levels of certain microRNAs are expressed in individuals with a traumatic brain injury. In this study, the researchers found that a panel of 14 different microRNAs together distinguished athletes with a concussion from the non-concussed athletes with 96% accuracy at the post-game time point. Certain microRNAs continued to show differences at the 36-48 hours post-game time point. Others showed significant changes across time points, potentially giving information about the underlying physiological processes happening after a concussion.

What does it mean for current athletes?

While the potential for saliva biomarker tests to diagnose concussions is an exciting development, it will be a while before this technology is on the sidelines of every high school football game.

First, far more research is needed. The findings need to be replicated with more studies in male athletes. It also needs to be studied in different populations. For example, biological differences may make the biomarker profiles different between male and female athletes. The normal processes occurring in the developing brain of children and adolescent athletes may also affect the way the microRNAs are expressed post-concussion. Some of this research is already underway.

Another issue lies with where and how the tests are conducted. While the saliva sample can be easily acquired on the sideline, the test can only be run in a lab setting at this time. The test could still be useful for diagnosing concussions in athletes, but it wouldn’t help with in-game return to play decisions. There is a critical need for objective sideline tests, as those who continue to play after a concussion are at a greater risk of prolonged recovery, over five days longer on average, than those who leave the game immediately after the concussion. It would also be financially and logistically challenging for high schools, middle schools, or youth athletic associations to purchase laboratory equipment for testing or store samples and transport them to a lab within a reasonable amount of time for testing. Although future technological advances will likely overcome this barrier, the current need for laboratory testing is a significant limitation for the practical utility of these tests.

Future studies will also need to examine the changes in microRNA over time. Changes were observed in the microRNA profile between the three time points. Some of the microRNA biomarkers may recover to baseline levels quickly, while others may linger. This has two important implications. First, the test may not be as accurate, or effective at all, if the evaluation is conducted several hours or days after the concussion occurred. Second, it isn’t clear yet whether or not these biomarkers will be helpful for tracking recovery from a concussion. Return to play decisions in the concussion recovery process still depend largely on athlete report of symptoms, and some athletes may say they are symptom-free when they are not so they can get back to play sooner. It’s possible that certain microRNAs or combinations of them may also be biomarkers of recovery, but more research is needed to make that determination.

What could this mean for the future of concussions in sports?

Although saliva microRNA tests aren’t ready for widespread commercial use yet, it seems likely that these tests will become a critical part of concussion diagnoses in the future. A handheld device that could quickly and accurately test the saliva on the sidelines would give clinicians an objective way to diagnose a concussion and remove athletes from play even when they deny their symptoms.

Concussion education and behavioral interventions will still remain a critical part of diagnosing concussions. Some athletes show obvious, noticeable signs of a concussion, but that isn’t always the case. The saliva test won’t be helpful to diagnose a concussion in an athlete who isn’t evaluated because they never report their symptoms.

It is also important to note that no single test is perfect. Even with a 96% accuracy rate, four out of every 100 concussions would be missed. Just like with computerized neuropsychological testing, like ImPACT, no single method should be used alone to diagnose a concussion. The researchers who conducted this study were careful to point out that the use of these biomarkers and other components of the clinical exam are likely related to each other and intended to complement each other. However, one is not intended to replace the other. If a patient is displaying clear impairments or has symptoms suggestive of a concussion, even if the saliva biomarkers are normal, the athlete should be considered to have a concussion and removed from the game. When in doubt, sit them out.

This new research is likely an early step towards the future of diagnosing concussions with an objective, easy to obtain saliva test. It is a exciting step forward in concussion research. Yet, critical steps still need to be taken, including research in different populations and the development of a sideline tool to test the samples. Thus, headlines like “New Saliva Test Can Quickly Diagnose Concussions” are true, but somewhat misleading. While the test does seem to quickly and accurately diagnose a concussion and shows great promise for the future, it won’t be showing up in your athletic trainer’s kit on the sidelines any time soon.

Did Lou Gehrig Actually Have Lou Gehrig's Disease? Brain Trauma, ALS, and CTE with Motor Neuron Disease

On June 3, 1941, Lou Gehrig died at age 36 of what was thought to be amyotrophic lateral sclerosis, or ALS. The famous New York Yankee was forced to retire from baseball as a result of the disease two years earlier. His battle with ALS brought attention to this rare and poorly-understood disease, and since his death ALS has come to be known as “Lou Gehrig’s disease.”

But some experts now question whether or not Lou Gehrig actually had the disease that was named after him. There is now evidence of an ALS-like disease associated with chronic traumatic encephalopathy, or CTE, the neurodegenerative disease thought to be caused by repetitive brain trauma. Gehrig played fullback on the football team at Columbia University, and he had a long history of concussions, including several incidents in which he lost consciousness. Yet, he played through these injuries, setting a record for playing in 2,130 consecutive baseball games.

"Lou Gehrig 001" by rchdj10 is licensed under CC BY-ND 2.0

ALS and Brain Trauma

ALS is a neurodegenerative disease that affects both the neurons, or nerve cells, traveling from the motor parts of the brain to the spinal cord and those traveling from the spinal cord to innervate our muscles for voluntary movements. Both of these neurons in the motor pathway, or motor neurons, are necessary for our muscles to contract and allow us to move. When these neurons are affected in ALS, it causes muscle weakness and eventually paralysis because signals cannot get from the brain to the muscle to initiate movement. Eventually the muscles involved in critical functions such as swallowing and breathing become affected, eventually leading to death. The average survival time after diagnosis is around three years, though a small percentage of patients will live for decades with the disease.

ALS is a rare disease. Globally the prevalence is around 4.4 individuals per 100,000 people in the general population. There are several risk factors for ALS, including older age, male sex, and having a family history of the disease. However, around 90% of cases are sporadic in nature and not linked to a family history.

Another risk factor is a history of brain trauma. The odds of being diagnosed with ALS are around 38% higher in those who have a history of head injury compared to the general population. Those who have sustained multiple head injuries are at a slightly higher odds of developing ALS than those who experienced just one head injury.

Several studies show that the prevalence of ALS is higher in athletes who are exposed to repetitive brain trauma in their sport. Compared to the general population in the United States, mortality from ALS is more than four times higher in NFL football players. Several studies have shown that the odds of dying from ALS are two to ten times higher in professional soccer players in Europe. One study found that the longer a soccer player played professionally, the greater their risk of dying of ALS.

The increased risk of ALS in contact-sport athletes is striking, but also concerning is the age that the disease is diagnosed. In Europe the average age of diagnosis of ALS in the general population is around 65 years old. In one study of European professional soccer players, the average age of ALS diagnosis was 45 years old. Another study found that the diagnosis of ALS before age 49 was substantially higher in professional soccer players. Given the short life expectancy after diagnosis with ALS, having an average onset 20 years earlier than the general population means most of these athletes died years or even decades before the average age most people are diagnosed with the disease. This diagnosis is devastating at any age, but a diagnosis in a person’s 30s or 40s exceptionally tragic.

It’s not known exactly how brain trauma leads to an increased risk of ALS, but there is some evidence that blood-brain barrier disruption might play a role. The blood-brain barrier is a highly selective membrane that regulates the passage of molecules between the blood and the environment around the neurons in order to protect the neurons from potentially harmful substances. Disruption of this barrier that can occur with brain trauma leading to alterations in the environment around neurons could play a role in the development of ALS. Mouse models have also shown that brain trauma can trigger pathology involving a protein called TDP-43, which is found in ALS as well as many cases of CTE.

To be clear, a history of brain injury doesn’t make the risk of getting ALS high. It is still a rare disease even in those with a history of either repetitive or a single brain trauma. The studies of athletes have only been conducted in professional athletes, and the vast majority of athletes never reach that level. At this time it isn’t known whether or not the risk of developing ALS is higher in those who play sports that expose athletes to repetitive brain trauma only through the youth, high school, or even college level.

CTE-Motor Neuron Disease

While the risk of ALS appears to be higher in former professional football and soccer players, there is some question as to whether these athletes actually have ALS or another disease.

In 2010 Dr. Ann McKee and her colleagues at the Boston University Chronic Traumatic Encephalopathy Center published the first study showing a variant of CTE in former athletes that was similar to ALS. In these cases, pathology seen in the brain in CTE also affected the neurons in the spinal cord, leading to symptoms during life that appeared to be caused by ALS. The connection to CTE could only be seen with postmortem examination of the brain and spinal cord tissue.

The prevalence of both CTE and CTE with the motor neuron disease is currently unknown. Without the ability to diagnose the disease during life, it isn’t possible to know how many people have the disease. In postmortem studies of former football players, the motor neuron disease variant of CTE was present in around 6% to 12% of CTE cases. However, individuals or their families are more likely to donate their or their loved one’s brain and spinal cord to research if they think they may have a disease, making this a biased sample. Far more research is needed to determine how common CTE with the motor neuron disease is.

Still, CTE with the motor neuron variant raises questions about the ALS diagnoses in former professional athletes. It is possible that at least some of those athletes may have had CTE motor neuron disease and not ALS. Without examination of their brain and spinal cord after death, there is no way for us to know.

And that bring us back to Lou Gehrig. It is clear that a disease with ALS symptoms took his life, but the underlying pathology that caused his symptoms has been questioned by experts in recent years. Given his long history of brain trauma, it is possible that he may not have had ALS, the disease that is named after him, he may have had CTE with the motor neuron disease. But without the ability to examine his brain and spinal cord, we will never know.

Youth Sports and Brain Safety: Which sports carry the greatest risk for the brain?

Our understanding of the consequences of brain trauma in sports, both concussive and repetitive "subconcussive" trauma, has grown immensely over the last two decades. With that has come growing concern from parents about the safety of their children playing sports.

Sports have so many benefits for children in a variety of areas, including physical and mental health, academics, and social life. Youth sports are a great venue for learning life skills, such as grit, determination, discipline, persistence, and teamwork. Every child should have the opportunity to reap the benefits of playing sports.

But which sports are the safest for a child's developing brain? And how can we make high-risk sports safer?

Concussion Risk

First and foremost, it is important to say that no sport or activity is without risk. Accidents happen, and concussions can happen in any sport or other activities in life. Yet, some sports come with a higher concussion risk than others due to the nature of the sport itself.

In the United States, football is consistently the sport with the highest overall number and rate of concussions. This is true across all levels of play. Each season, around one in twenty youth players under age 14 sustain a concussion each season. Nearly 100,000 youth and 80,000 high school football players sustain a concussion each year.

Other sports carry relatively high concussion risks. Though hockey is often second to football among common sports in the United States, rates have declined over the last decade as a result of a ban on checking in the boy’s game before age thirteen. Soccer falls just behind hockey in most studies, but it is the sport with the highest rate of concussions for females at all levels. Concussion rates in lacrosse, wrestling, and competitive cheerleading are also concerning. Rugby is popular internationally and a growing sport in the in the United States, and it carries a concussion risk similar to football.

A few studies have found higher concussion rates in girls’ soccer or hockey than football, but those are in the minority. The vast majority of concussion epidemiology studies show football has the highest concussion rate. But ultimately, those details don't matter. One sport carrying dangers for the brain doesn’t somehow make another sport safe. All of these sports carry a higher concussion risk, and we should be taking steps to improve brain safety in all of them.

Repetitive "Subconcussive" Impacts

A growing body of research shows that repetitive brain trauma causes changes in the brain over the course of a season and career, regardless of whether or not those impacts result in concussion symptoms. These impacts are sometimes called “subconcussive.” Chronic traumatic encephalopathy (CTE) has been diagnosed in individuals with no known history of concussions but who were exposed to repetitive subconcussive impacts through sports or other exposures. (Though it is important to note that many concussions go undiagnosed, and it is possible, if not likely, that some of those individuals sustained concussions that were never reported.)

Which sports carry the greatest risk for repetitive impacts? I have a chapter of my book dedicated to head impact exposure in sports. Here’s a brief summary to address this question:

Research using accelerometers placed in helmets, mouth guards, patches, or headgear have given us valuable insight into the number and force of impacts athletes sustain in their sport. Football carries the highest average risk for repetitive brain trauma in athletes in the United States. The average high school and college football player experiences hundreds of impacts over the course of a season. In fact, it is common for some athletes studied to have sustained over 1000 impacts, with a few incurring over 2000 impacts in just one season. At the high school level, it is more common for athletes to play both offense and defense, greatly increasing impact exposure. Linemen tend to have higher overall impact numbers, while wide receivers and defensive backs tend to experience higher-magnitude impacts.

You might think that smaller, slower youth athletes can’t hit that much or that hard, but that isn’t true. Youth football players ages 9 to 14 average 200-300 impacts per season, with several experiencing hundreds more. Even the youngest players average over 100 impacts per season. This is despite the fact that the average youth season involves far fewer practices and games than the college or high school season. These impacts are of similar magnitudes to those experienced by the older players, despite their smaller size. This may be because a child’s head grows quickly, making it disproportionately larger than the rest of their body. Like a bobblehead doll, their smaller, weaker necks have a difficult time stabilizing their head, and the weight of a helmet makes this effect even worse.

Though less than football players on average, hockey players can also experience hundreds of impacts each season, including many high-force impacts. Studies of soccer impacts suggest that hits are less frequent overall compared to hockey and football, but they can still exceed 100 in a season. These studies may also be deceiving, given how common it is for soccer players to play year-round and in multiple leagues at the same time. There is limited research on other sports like rugby and lacrosse, especially at the youth level, but early evidence suggests that they tend to expose athletes to impacts at similar levels as football and hockey.

Which sports are safe for the brain?

There are many non-contact or limited contact sports that don’t involve repetitive impacts and carry lower concussion risks. Concussions can still happen in any sport, including basketball, softball, baseball, or volleyball, but the repetitive subconcussive impacts aren’t part of those sports.

For contact sports, the numbers I just presented are concerning, but that doesn’t mean we should be eliminating or avoiding sports like football, hockey, soccer, and rugby altogether. Instead, there are ways to enjoy these sports without the repetitive impacts and high concussion risk. Alternative versions of these sports, or versions with specific rules for the youth level, can be great ways to get kids involved in sports without the greater risk to their brain.

Hockey has banned checking prior to age 13, and concussion rates, as well as overall injuries, have dropped since. Soccer delayed the introduction of heading until age 11, and limited it until age 13. While age 11 may still be early to introduce heading, the delay is a step in the right direction. As I described in an earlier blog post, flag football players experience substantially fewer impacts than tackle football players, while still learning about the game and developing football skills. Other non-tackle forms of football, such as TackleBar and Flex Football, can also be great, safer options.

If athletes do start to play the full contact form of these sports, head impact exposure can still be greatly reduced by substantially limiting or completely eliminating checking, heading, or tackling in practice. For example, many elite high school and college teams have chosen to eliminate tackling from most or all practices. The athletes can still successfully tackle in games without practicing on each other, and the athletes tends to stay healthier overall throughout the season. Coaches make the choices about drills and tackling in practice, and they also create the culture of safety, or lack thereof, on the team. Some coaches value brain safety, concussion reporting, and minimizing contact over a season. Other coaches create a culture that discourages athletes from reporting concussions and valuing their health. When rules or laws limit contact practice time, some coaches simply pack as much contact into the limited time as possible, exposing their players to just as many if not more impacts as they experienced prior to the law. Parents and athletes should feel comfortable with the culture around safety created by the coaching staff before joining a team.  

Given the rapid brain development happening in a child’s brain and evidence for potential disruption of these processes, avoiding the full-contact form of high-contact sports before high school is ideal. Though some coaches and leagues may promote “new” and “safer” techniques, the data isn’t there to show these techniques make a meaningful difference in brain safety for youth players. Not only does delaying the introduction of the source of repetitive impacts allow more time for brain development, but it also reduces the overall number of impacts experienced by athletes over their lifetime, which has been linked to long-term cognitive, mood, and behavioral difficulties and the development of CTE. While the risk is not zero, current evidence suggest that only playing a few years of high school football, especially when contact is minimized at the high school level, leaves athletes at low risk of developing CTE.

Brain safety in sports isn't an all-or-nothing issue. With strong measures to eliminate impacts at youth levels, even traditionally high-risk sports can be played in a low-risk way, giving more opportunities for kids to thrive in sports with minimal likelihood of short- and long-term consequences for their brain.

How many concussions have you had? Why providing a clear and detailed concussion definition is essential

Have you ever had a concussion? How many concussions have you had in your lifetime?

Many people underestimate the answer to these questions, not because they are trying to hide the real answer, but because they don’t know what qualifies as a concussion. It is a common misconception that, to have a concussion, you have to lose consciousness or have significant symptoms that last for a long time. As a result, many go undiagnosed because the person doesn’t know that the symptoms they are experiencing are enough to be considered a concussion.

There is one easy way to solve this problem. It doesn’t require intensive concussion education or hours of training. In fact, it can be done in under 30 seconds on the sideline, in the athletic training room, in the doctors office, in an emergency department, or any other setting. The solution: provide a clear and thorough concussion definition.

Several studies have shown that the number of reported previous concussions increases after participants are given a detailed concussion definition. In our research at the Boston University CTE Center, we asked participants how many concussions they had in their lifetime. Then we gave them this definition:

“Some people have the misconception that concussions only happen when you black out after a hit to the head or when the symptoms last for a while. But, in reality, a concussion has occurred anytime you have had a blow to the head that caused you to have symptoms for any amount of time. These include: blurred or double vision, seeing stars, sensitivity to light or noise, headache, dizziness or balance problems, nausea, vomiting, trouble sleeping, fatigue, confusion, difficulty remembering, difficulty concentrating, or loss of consciousness. Whenever anyone gets a ding or their bell rung, that too is a concussion.”

In a 2014 CTE Center study of 466 current and former athletes from a variety of sports (48% football, 88% male), 73 percent of the athletes increased their estimate of their lifetime concussions after hearing the definition. The athletes reported, on average, double the number of concussions after hearing the definition. The pre-concussion average was seven, while the post-definition average was 15 reported concussions. These results were similar regardless of the level of play the athlete reached or whether they played a contact or non-contact sport.

Another CTE Center study found even more striking results in former NFL players, who reported an average of five times more concussions after hearing the definition. These athletes may have been basing their original number off of what was considered a concussion in their playing days decades earlier.

Other recent research has had similar findings. A quarter of Icelandic elite female athletes changed their answer from having sustained no sport-related concussions to having had one ore more after being given the definition, with 16 percent of those changing from zero to four or more concussions post-definition. Thirty percent of youth and high school athletes in another study reported more previous concussions after being provided the concussion definition. Both of these studies used the definition above, but the former added “Whenever anyone gets dazed after a blow, that too is a concussion. Note that a direct blow anywhere on the head and body with an impulsive force may cause a concussion.”

This research shows that providing a clear and comprehensive concussion definition is critical to getting a more accurate answer, both when asking about the number of concussions a person has sustained, or if they have ever sustained a concussion at all. I can tell you from my personal experience, after giving the concussion definition, I have had former athletes tell me they sustained hundreds or thousands of concussions. Some said it happened almost every time the played their sport.

When taking a concussion history, whether as part of a preparticipation exam or during a patient’s concussion evaluation, whether in a sport-related setting, a clinic, or a hospital, it is essential that all clinicians provide a concussion definition like the one above. This will clarify for the patient what a concussion is and increase the likelihood that they will provide an accurate concussion history.

Concussion research should include a similar concussion definition. It is likely that studies using self-reported concussion histories have historically underestimated the actual number of previous concussion sustained by athletes. Some studies only ask about diagnosed concussions, despite the fact that many concussions go undiagnosed. In other studies, it is likely that many participants underreported their previous concussions because they didn’t know that what they had was a concussion.

A thorough concussion definition should also be incorporated in concussion education so that athletes are aware, in the moment, that what they are experiencing qualifies as a concussion. It may increase the likelihood that they seek care for their injury.

I have had athletes that were surprised after hearing that definition, unsure how many concussions to tell me they had experienced in part because they couldn’t believe the number was so high. I think many athletes likely feel the same way, but because research has historically presented a lower average number, they feel that their estimate couldn’t be accurate, even if it is. They aren’t exaggerating. They are sharing what they have actually experienced. And in some cases it was so common it was impossible to accurately estimate. Yet they never sought care in the majority of those cases.

We shouldn’t assume that people know what a concussion is, even if they have had concussion training or they play a contact sport in which concussions have been a greater part of the conversation in recent years. It isn’t enough to simply ask, “Have you ever had a concussion?” or “How many concussions have you had?” Providing a detailed concussion definition is a quick and simple way to give athletes and other patients necessary information to know what qualifies as a concussion.