Study: More than 80 percent of football concussions go unreported

By now, it's well-established that the concussions suffered by many football players can lead to long-term mental problems.

But among the many questions researchers face, one is particularly vexing: How often do these concussions actually occur?

This is so tough to figure out because concussions frequently go unreported in football. For years, concussions were considered a minor injury and many players simply played through them. Today, even with stricter protocols in place at the NFL and college level, some players (and perhaps coaching staffs) actively hide concussions, so they can avoid missing playing time.

for every single diagnosed concussion over the players' careers, they had four suspected and undiagnosed ones

A new study provides a rough idea of just how often this under-reporting occurs. Researchers from Harvard and Boston University surveyed 734 college football players from ten schools on how often they'd been diagnosed with concussions, how often they suspected having concussions but didn't get diagnosed, and how often they suffered "dings" or "bell ringers" (slang for rattling blows to the head that may or may not cause concussions).

It turned out that for every single concussion suffered over the course of these players' careers, they also had four suspected — but unreported — concussions, and 19 so-called "dings." And other data collected, on symptoms experienced by players, suggests that many of these "dings" were, in fact, concussions.

In other words, if these numbers are accurate, more than 80 percent of concussions don't even get officially counted.

The data on unreported concussions

Previously, estimates for the percentage of concussions that are actually diagnosed and reported ranged from 50 percent to 75 percent. These estimates, though, were mostly based on old data, with smaller sample sizes.

The new data set comes from surveys filled out by players at ten schools in the NCAA's (confusingly-named) Football Championship Subdivision, which is basically the level just below big-time Division I football. Among other things, the players were asked the number of concussions they'd had over the course of their careers so far, the number of times they suspected having concussions but didn't get them diagnosed, and the number of times they got a "ding" or had their "bell rung." Here were the averages:

Officially diagnosed concussions represented a pretty small percentage of all concussions the players thought they'd suffered — something that many researchers have previously suspected.

Players were also asked how often they felt concussion-like symptoms after a "ding" (specifically, how often they felt dizzy, vomited, lost consciousness, saw stars, forgot what they were doing on the field, got headaches, or had problems concentrating in the week afterward). The average player experienced between one or two instances of each type of symptom during the 2012 season. This means that, in all likelihood, the players had suffered more than the 2.64 concussions they suspected in their careers — and some of those "dings" had, in fact, been concussions.

Finally, the players were asked how often they returned to a game or practice while still experiencing these symptoms. On average, they'd done this 6.65 times during their college career, and 1.74 times in the previous season. The reason this is such a big deal: playing football while still experiencing concussion symptoms dramatically increases the chance of a repeat concussion, and may increase the chance of long-term problems.

Which positions suffer the most concussions?

Offensive and defensive linemen seem to suffer more unreported concussions. (Ronald Martinez/Getty Images)

The researchers also sliced all their data by football position, in order to investigate a widespread hypothesis: that offensive and defensive lineman suffer a disproportionate number of undiagnosed concussions.

The reason they believe this is that even though these players experience lower-speed impacts than receivers and defensive backs, they slam into each other on virtually every play. Further, their impacts are less noticeable to observers, making it more feasible for them to hide their symptoms and keep playing.

The data suggests that this suspicion may also be accurate. Although diagnosed concussions occurred at relatively similar rates among all groups, offensive and defensive linemen suffered slightly more suspected (but undiagnosed) concussions, and offensive linemen experienced more "dings." Offensive linemen also suffered from all the various symptoms — and returned to play with them — disproportionately more than any other position group.

Is there any solution to concussion underreporting?

(Hunter Martin/Philadelphia Eagles/Getty Images)

If this survey accurately represents football at other levels — both college and pro — it says two things.

1) Despite new rules — or perhaps because of them — players still aren't reporting all concussions, and are returning to play when they shouldn't be.

2) Linemen (especially offensive linemen) suffer the highest number of unreported concussions, and play through them most often.

It might be fair to question whether this data is similar to what you'd find at top-level college football and the NFL. Training staffs and budgets are larger at those levels, and there may be more attention paid to players. At the same time, the stakes are much higher for both players and coaches, so there may be even more reason to hide symptoms and keep playing.

players have short-term incentives not to follow concussion protocols

This kind of thing is tough to fix. Creating protocols that force a player to pass tests in order to return to action (as the NFL has done) is one thing. Actually getting all players to follow it — when they specifically have short-term incentives not to — is another.

One possible solution, mentioned by the researchers, is the use of in-helmet sensors to measure the impact of hits. If that sort of objective number was automatically gathered and sent to trainers, it could make it easier for them to be aware of all concussions and ensure that players don't return to play prematurely.

Read more: Here's what we know about football, concussions, and the brain

The NFL's concussion crisis, explained

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