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From Little League to college football to the World Cup, sports is a huge industry. We play on neighborhood teams as kids, root for our favorite professional athletes, and buy millions of dollars’ worth of branded merchandise each year.

But even if you don’t personally care what the next big sportsball thing is, you’ve probably heard about what’s happening with head injuries causing dementia in football players. When I say “football,” I mostly mean American football, because that’s what most of the news and research has been about. But it’s not just the NFL that has the problem.

We’re learning that concussions from soccer, aka football for most of the world, can lead to dementia, too. And there are serious injuries that come with all kinds of other sports that have only recently been taken seriously. We know that physical activity is super important for staying healthy, so it’s pretty great that our society values athletic achievement.

But sports-related injuries are expensive, painful, and can have lifelong effects, some of which we’re only just discovering now. Some researchers are starting to think that for some sports, the risk of injury could outweigh the benefits of playing. But giving up on sports or completely changing the way games are played isn’t really a practical solution.

Football isn’t just gonna disappear, and most people wouldn’t want it to. So researchers, coaches, and doctors have two main priorities: learning as much about the effects of sports injuries as we can, and finding ways to protect players without completely changing how the game works. When it comes to risky sports, American football has been the big one in the research so far.

It’s a high-contact sport where players are prone to all kinds of injuries. But even though there have been professional leagues since 1892, it’s only in the last 25 years that doctors have really begun to examine what’s happening to players’ heads. And they’re becoming increasingly concerned about the relationship between head injuries and a neurodegenerative disease called chronic traumatic encephalopathy, or CTE.

It’s chronic because it’s long-term, traumatic because it comes from physical trauma, and encephalopathy just means “brain disease.” But as brain diseases go, it’s a bad one. Symptoms range from confusion and disorientation to memory loss, speech disorders, impulsive behavior, depression, and suicidality. Essentially, it’s a form of dementia, but it shows up much earlier than most other types, usually when the person is in their 40s or 50s.

And it seems to be caused by repetitive head injuries. The thing is, head injuries happen all the time in football. A major part of the sport literally involves slamming people to the ground.

And, as we know from our good friend Isaac Newton’s first law, things in motion want to stay in motion. Including brains. So when the motion of your head is suddenly stopped, like when it slams against another player’s knee as you dive for a fumbled ball, the inertia of your brain keeps it moving forward … until it hits your skull.

You have some fluid in there to cushion your brain against normal jostling, but it can only do so much protecting. If a hit is hard enough, the brain literally rattles around inside the skull, which can bang up, stretch, and even break brain cells, interrupting their normal blood flow and chemical signaling. That’s what we call a concussion, and it can take a month for the brain to get things back in order afterward.

Now, it’s not like anyone thought head injuries were good for people. But the effects were believed to be somewhat short-term. Then retiring NFL players started describing something else: lasting disabilities from head injuries they’d received on the field.

Growing concerns led the NFL to create the Mild Traumatic Brain Injury Committee in 1994. Its main goal was to make sure that players were immediately assessed and treated for possible concussions. That was a start, but the NFL still argued that the so-called “concussion issue” was being overblown by the media.

Then, in 2002, a doctor discovered CTE in the brain of a football player who’d died. People were skeptical at first, including the NFL. But over time, researchers discovered more and more cases of football players with CTE.

At first, they thought it was just concussions that were the problem. But we now know that any kind of repetitive head injury can cause CTE. And evidence suggests that it’s really common in NFL players.

For example, a 2017 study looked at the brains of 111 former NFL players and found that 110 of them, 99%! had evidence of CTE. Since the brains were donated, the sample was super biased towards players with suspected. CTE or similar brain damage, but that’s still about a tenth of all NFL players who died since the study began in 2008.

So at the very least, about a tenth of NFL players end up with CTE. At most, close to 100% of them do. Researchers think CTE happens because players receive so many hard hits that their neurons don’t get the chance to recover after an injury before the next trauma.

So cells become irreversibly damaged, or even die, making the brain atrophy and shrink. It can take years or even decades for CTE to fully manifest, but there’s no way to detect it early on, when interventions could be most helpful. Doctors diagnose CTE by looking for what are known as hyperphosphorylated tau proteins, which also show up in other degenerative conditions like Alzheimer’s disease.

And you can’t just open up someone’s brain to examine their proteins while they’re alive, so they can only diagnose it postmortem. Normally, tau proteins help stabilize the structural proteins within cells. But hyperphosphorylation changes their molecular structure in a way that makes them tangle up and get in the way of normal cell functioning, eventually killing cells.

Kill enough brain cells, and the person ends up with dementia. In the past decade, the NFL has changed some rules to prevent at least some concussions, and it has a whole set of requirements players have to meet before they can start playing again if they do get one. But concussions still happen all of the time, and the guidelines don’t help with other hard hits to the head.

Meanwhile, the increased awareness of the condition has led to doctors noticing it in other sports, too. CTE has been seen in mixed martial arts fighters, hockey players, soccer and rugby, and even in professional wrestlers! And most recently, researchers have found evidence for it in kids.

A 2018 study in the journal Brain examined, well, the brains of eight teenage athletes with histories of concussions that died young. And the researchers found that one in four had those distinctive tau proteins, the signs of degenerative damage. The others had signs of inflammation and damaged brain cells; the kinds of things believed to lead to CTE.

So it’s possible that the beginning stages of CTE can start really early on, from just a few hits to the head. You might think it would be easier for younger athletes to go for sports with less player-on-player violence, like cheerleading or gymnastics. But they can carry significant injury risks, too.

In the US, cheerleading is second only to football in the amount of money spent on student athlete insurance claims. From 1990 to 2002, over 200,000 kids were treated in hospitals for cheerleading injuries. And a study from 2009-2014 found that the most common cheerleading injuries, about a third of them, were, you guessed it: concussions.

Cheerleading is dangerous enough that the American Association of Cheerleading Coaches and. Administrators developed a whole set of rules meant to protect athletes back in 1984. But even with oversight, sports can cause lasting injuries when athletes are pressured to start young.

Take gymnastics, for example. Since being small has a ton of advantages when it comes to the physics of twists and flips, gymnasts tend to specialize in the sport when they’re very young. Specialization means more training, for longer periods, with more targeted kinds of exercises and goals.

It also increases an athlete’s risk of both sudden onset injuries, like sprained ankles, and overuse injuries, like tendinitis, where the tissue connecting bones and muscles gets irritated or inflamed. Landing hard on thin mats over and over again can also cause stress fractures in your legs, as well as injuries in your wrists, knees, back, and ankles. While getting a sprain or tendinitis once might not seem like that big of a deal, research has found that more than 40% of people with these kinds of injuries develop chronic conditions like osteoarthritis down the line.

That’s a painful degeneration of the cartilage cushion between joints. They can also lead to osteoporosis, fragile bone tissue that’s prone to breaking. And because yes, there are more problems, there’s research suggesting younger athletes have more spinal abnormalities from repeated stress on their growing bones, making them at higher risk for chronic pain as adults.

That’s a lot of potential health problems. And it’s not like specialization and overly-intense training are limited to gymnasts. Kids as young as 8 and 9 can need surgery for damaged elbow ligaments from pitching too much while playing baseball.

And some overuse injuries are so common that they’re named after the sports that cause them, like swimmer’s shoulder or runner’s knee. There’s no easy solution to any of this. But the good news is, all this knowledge about sports injuries is starting to change how we approach physical activities.

Injuries that might have slipped under the radar in the past are now being noticed and treated sooner, before they become irreversible. And research into the long-term consequences of injuries, like what’s been done on head trauma and CTE, is helping develop better training guidelines that protect athletes. For kids, for example, the American Academy of Pediatrics’ official recommendations say that they should train for fun and social interaction, not for intense contests.

Then, competitiveness can ramp up as they get older because their bodies can handle more once they’re more mature. Which, okay, these guidelines are meant for pediatricians, not parents. But what doctors tell parents and coaches can change the way we approach this stuff.

The AAP also recommends playing a bunch of different sports instead of focusing on just one, because that reduces the injury risks that come with specialization. And research suggests that early specialization isn’t necessary for athletic success later in life, anyways, so there’s not really any reason to do it. But what about adults, especially when it comes to CTE?

Well, it helps that we’re developing better tools of the trade. Sports engineers are using the latest research to build better sports equipment, like safer helmets. But even the best equipment isn’t going to prevent all injuries.

So the other part of the solution is to try to make the sports themselves safer. Some organizations have already changed some rules, like in 2010 when the NFL started forbidding certain kinds of hits to the head and neck. But there are definitely more changes that could be made to reduce injuries, like developing better techniques, safer tackling methods, for example.

Having more severe punishments for players who do things that are deliberately dangerous would probably help too. Still, there’s no perfect or easy way to fix this. If there’s anything we’ve learned from the last decade’s worth of research on sports injuries, though, it’s how much we don’t know.

And with more research into the ways these injuries happen, hopefully we’ll also find out more ways to prevent them. Because yeah, sports are great, and we’re gonna keep playing them. But nobody one wants people hurting themselves.

Thanks for watching this episode of SciShow! SciShow is produced by Complexly, a group of people with a shared thirst for knowledge. You might already be familiar with some of our other channels, like Crash Course.

And if you liked this video, you might want to check out our show Healthcare Triage, where. Dr. Aaron Carroll gives you the rundown on all things medical science, from the opioid crisis to the truth about cancer risk.

Just head over to youtube.com/healthcaretriage to learn more. [♪ OUTRO].