McKelvey School of Engineering

What a lifetime of playing football can do to the human brain

Football isn’t just a contact sport — it’s a dangerous game of massive bodies colliding into one another. And while it may seem obvious that this sport can do extraordinary damage to brains and bodies, it’s taken far too long for the NFL, the medical community, and football fans to fully reckon with this.

Doctors have learned a tremendous amount about concussions and chronic traumatic encephalopathy, or CTE, a degenerative brain condition believed to be caused by repeated hits to the head, since the first former NFL player was diagnosed with CTE in the early 2000s. Concern around the issue has only grown now that more than 100 former NFL players have received a postmortem diagnosis of CTE, and new research is finding that youth football may be a risk factor for CTE down the line.

Football is still an immensely popular sport in the United States, and this weekend, millions will watch and enjoy the Super Bowl. But all the evidence we now have about the very serious risk of brain injuries casts a dim light on the future of the sport. Here’s what you need to know.

1) Concussions are incredibly commonplace in professional football
The human brain — the most complicated and powerful organ on planet Earth — is squishy. And when a person hits their head hard, the brain can bounce around and twist in the skull. It’s this rapid motion of the brain inside the skull that creates the traumatic brain injury known as a concussion.

During impact, individual neurons can be stretched and damaged. Brain chemistry gets out of whack. Concussions make people “see stars,” become disoriented, lose consciousness, become sensitive to light and sound, get headaches, and have sluggish or confused thoughts for weeks and even months.

Heads and bodies get smashed and shuddered every week during the football season. And despite changing the rules to allow for more severe penalties and fines for flagrant helmet-to-helmet hits, the NFL has not succeeded so far in preventing concussions.

The number of concussions sustained during practice and gameplay in 2018 fell somewhat, from a total of 281 in 2017 to a total of 214 in 2018, according to the NFL’s injury data. And then increased again to a total of 224 in 2019.

This data doesn’t cover the countless additional blows to the head that don’t reach the level of concussion but still may pose a risk for the brain.

2) Chronic traumatic encephalopathy is a degenerative brain disease caused by repetitive hits
CTE is not about single concussions. It’s the result of repeated concussions — and even head impacts that are not quite as severe — which can result in lasting structural changes in the brain. “The pain you feel [after a hit] is not necessarily an indicator of the damage that does to your head,” Philip Bayly, an engineering professor at Washington University in Saint Louis, who has been studying the mechanics of brain movement inside the head, said in a 2019 interview.

Specifically, brains with CTE accumulate a protein called tau (which is believed to be dislodged from brain fibers during an injury). Tau clumps together in the tissues of the brain, interrupting critical information flow.

The mechanisms of how this all happens still aren’t well understood. “The challenge is nobody sees what happens to the brain when someone gets a concussion,” Bayly said. One hypothesis is that the sulci — the grooves on the surface of the brain — experience high mechanical stress during an injury and burst open pockets of tau. (In autopsies, these clumps of tau are often found near the blood vessels at the bottom of sulci.)

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