We’ve seen NFL players have less risk of cardiovascular disease, and cancer…and they live longer than the general population.
–Wait, former NFL players are healthier than most people?
(They also have less risk of domestic violence.)
What we didn’t see there though was NFL players having healthier brains. Neurodegeneration is more likely to kill a former NFL player, albeit at what will be for most, an apathetically increased rate.
This will not be a political post, but we have to go there briefly-
When it comes to adults, I’m, and I’d say many -in America at least- are of the belief as much as we can, so long as it’s not hurting others, let people do what they want. If grown men want to launch themselves into one another, damaging their brains? Have at it.
The issue then is kids. Playing football is on the precipice of being considered smoking and drinking. You can do it as an adult -with some rules- but you can’t do it as a kid. You’re not 18 or 21? Then you’re not old enough to consciously decide to expose yourself to that harm. Because we can’t always rely on parents, government steps in.
First though, we need to quantify the harm, or lack thereof, with playing football as a kid. This is not easy with NFL players, never mind kids. Mainly because
- diagnosis is primarily done postmortem
- there is an enormous selection bias.
With 2., we mean the families donating brains are the most suspicious football was a contributor to the person’s negative health before they died.
With NFL players, we get further into their lives while still playing football. If you play til 30 and die at 60, you played half your life compared to a kid who stopped at 18.
All that said, what have we found so far? Looking at one of the most recent studies:
Housecleaning:
-This study did not only look at football players. Collision sports also consisted of rugby, lacrosse, and hockey.
-The authors looked at some common biomarkers of brain health. The two we will be discussing are fractional anisotropy and mean diffusivity. They sound scarier than they are. More on them in a second.
What’s most important to remember at this stage is biomarkers are not the same as clinical markers. One of the biggest pitfalls of health research is studying by proxy. The muscle hypertrophy world is notorious for this. We’ve had studies where we find the markers of hypertrophy are elevated, only to find, once putting a tape measurer around the bicep, the muscles didn’t actually grow. Many a theories have been born and died by this approach.
-> With hypertrophy, the markers of anabolism may be elevated…but so can the markers of catabolism. IF you look for them.
One of the big issues with chronic traumatic encephalopathy, CTE, is the thought the disease hits later in life. The subjects in this study were 21 years old. Thus, we are studying by proxy, and, this cannot be overstated, GUESSING. It’s not bad. It’s what we’re able to do right now.
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Fractional anisotropy and mean diffusivity
Short version:
Fractional anisotropy examines in what direction a substance, water in this case, flows. If the water can flow every direction evenly, that’s called isotropic. Iso meaning equal all around. That’s a low fractional anisotropy.
If the water only flows one direction, that would be a very high fractional anisotropy.
Mean diffusivity is the rate at which diffusion happens. If water can go every direction, it can diffuse more quickly. If only one direction, the rate is likely less.
Thus, when fractional anisotropy is high -water only going one direction- mean diffusivity tends to be low, and vice versa.
Long version: I’m going to quote another paper to define these. Feel free to skip to the bolding if you wish to avoid the academese:
“Using tensors, adapted from the field of engineering, the average shape of the diffusion is characterized as more or less spherical when there is no impediment to water diffusion, as for example in cerebrospinal fluid (i.e., unrestricted water is free to diffuse in all directions: isotropic). However, the average shape of the diffusion becomes more elongated, or cigar shaped, when there is a preferred orientation in which water is restricted, as for example in white matter. Here, water diffuses freely in directions parallel to axons but it is restricted in directions that are perpendicular to the axons, which results in the magnitude of the diffusion along the axons being larger than the two perpendicular directions, leading to an elongated ellipsoidal shape of the diffusion tensor, described as anisotropic.
There are various ways that the shape and size of a diffusion ellipsoid can be quantified, but the two most common indices used are Fractional Anisotropy (FA) for shape, and Mean Diffusivity (MD) for size. FA is a scalar measure that ranges from 0 to 1, with 0 being completely isotropic, meaning that water diffuses equally in all directions, and 1 depicting the most extreme anisotropic scenario in which molecules are diffusing along a single axis. Accordingly, in cerebrospinal fluid and gray matter, as noted above, the direction of water is equal in all directions (i.e., isotropic), and the value is close to 0.
In contrast, in white matter, for example in the corpus callosum, the water is relatively free along the axons, but restricted perpendicular to the axons, and therefore more anisotropic, with FA being closer to 1. Thus in white matter, reduced FA is generally thought to reflect loss of white matter integrity that may reflect damage to myelin or axon membrane damage, or perhaps reduced axonal packing density, and/or reduced axonal coherence.
“FA and MD are frequently observed as being inversely related.”
The bolding is crucial. The current thinking is various sections of the brain start with an optimal fractional anisotropy and mean diffusivity. In response to say, a traumatic brain injury, or aging, we observe anisotropy to go down and diffusivity to go up.
–Adult brains undergo structural changes earlier than we thought
–Cognitive activity, cognitive function, and brain diffusion characteristics in old age
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So what did our study find in regards to collision sport athletes?
“The collision group had significantly elevated FA and reduced MD in white matter, compared to both contact and non-contact groups.”
Yes, that’s right. Collision sport athletes had signs of IMPROVED brain health. From the discussion:
“It is important to note that the trends in this study were opposite to those seen in more severe TBI, where decreased FA and increased MD are commonly reported markers of axonal injury. Thus, both concussion and participation in collision sports showed microstructural effects that appear to be distinct from the pathophysiology of more severe TBI.
Why would this happen?
“The cause of elevated FA and decreased MD in this cohort has not been definitively established, but may reflect adaptive growth processes in response to neural injury, e.g., axonal budding or gliosis. Alternatively, these effects may be due to structural reorganization of white matter, either to compensate for greater frequency of impacts, or in response to specific cognitive demands associated with collision sports. This is an important area of future research, where more advanced diffusion-weighted techniques may provide improved neurobiological specificity.”
WHOA! That’s pretty damn different than what we’ve been hearing about, no??? The current thinking has been concussions, and even subconcussive blows to the head, are all bad. That there is no amount of hitting your head that’s healthy. Yet the markers of a serious brain injury are not matching up with those of lesser head impacts. This is critical: we’re not saying these collision sport athletes were even trending that direction. They trended the opposite direction.
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What the hell is going on?
Imagine a golf ball suspended in this water:
My hunch is you can think of that golf ball as your brain within your skull. That when we walk and run, the brain does not sit perfectly in the skull. Rather it gets bounced around.
-> Tangents of this analogy have been used before, here and here for example.
In every scenario where we bounce our bodies around, there is a continuum of health. Do it not enough? We atrophy and get sick. Do it a medium amount? We increase our bone density and get healthier. Do it too much? We break down.
For example, ride a bike, ala:
And bone density will not improve. Professional cyclists are renown for osteopenia (a precursor to osteoporosis). Mountain bikers though? Where there is some jarring to the body? They do just fine.
The brain also responds mechanically to exercise. Think of a tempurpedic / memory foam pillow. Initially, it’s very responsive to pressure. You push on it, release, it comes back quickly. After it gets worn out, it doesn’t come back as quickly. It’s mushier. This study found this happens to the brain!
–Firmer, fitter frame linked to firmer, fitter brain <- Important to note the subjects were tested on a treadmill, not a bike.
What I bet we could be seeing with these collision athletes is they are moving around to a degree which is beneficial for the brain. Enough so to outweigh potential negatives. Much like a high school runner, they haven’t hit that threshold where running starts to break their body down. That doesn’t happen for most until college or professional.
-> I’ve long believed children love to run around, throw their bodies everywhere, be picked up, be thrown in the air, because it gives them banging on their body. I don’t think it’s a coincidence peak brain development coincides with peak movement. (Kids move more than adults.)
No negative cognitive impacts from playing high school football:
–Association of Playing High School Football With Cognition and Mental Health Later in Life
In the above study, high school football players actually had a lesser risk of depression, and 32% less chance of alcohol dependence. (Note this study is not a biomarker study, but looked at actual diagnoses.)
With the subjects of our original study, we’re talking college athletes at the University of Toronto. Not exactly a school oozing with sporting prowess.
No, we’re not saying you want your kid to play football, but think of it this way: You want your kid to run around for their musculoskeletal system. Do you want them to train for a marathon for that health? No.
As the authors say though, there are potentially some benefits of collision sports not happening in other activities. I wrote about this in the first NFL post. What I would add here is I could easily see a case where a person cannot fully engage their brain power without the threat of violence. That those partaking in activities where regularly guarding for your life happens, may engage the brain to a degree which otherwise doesn’t happen. In other words, Fight Club.
However, as a theme of this site goes, when you gain something, you lose something. That extra brain intensity comes with the tradeoff of increased brain risk. So no, I wouldn’t want my kid playing football, at any age.
- Whether brain plasticity from violent sports causes a benefit worth attaining is doubtful.
- A powerlifter has more bone density than a recreational lifter, but that bone density isn’t necessary for great health.
- The risk of a traumatic brain injury reversing whatever benefits they could get is always there, at an increased rate compared to nearly all other activities.
- At some point a threshold could / will be reached.
My hunch with 2. is the NFL is obviously a threshold. Not for everybody, but for more than 50%, where you have to worry about the average player. I’d bet division I is at this threshold too.
With high school, I doubt the average case is much a concern. High level high school though -competing for state championships, went to a school with over a thousand people, in a densely populated state, at least a handful of players get seriously recruited each year- and I’m worried.
We could again view it like the rest of the body. There’s not much concern about serious injury in high school sports. We worry more in college and even more professionally.
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Now politically, that’s not how we operate. We’re much more black and white. Just like we don’t genetically screen for who will be fine smoking and who won’t, we’re not going to segment high school players by size, speed, location and say you can and can’t play football. (At least not any time soon.)
The final point here is there are rarely moments of human health where we can paint a brush and say something is universally bad. The only two instances I’ve come across are trans fats and smoking. It’s very hard to come across a context where doing those on any regular basis is worth it. (But really, it’s more you can’t make a case those have any benefits, opposed to they’re always bad. Again, we’ve all heard of smokers who live past 90.)
-> This is one of the biggest dieting pitfalls: going to extremes of “This food is bad / great.” For example, artificial sweeteners. If they help you avoid eating cookies because it treats your sweet tooth, thus keeping you from obesity, then it can easily be argued you should be consuming them.
–> We’re not terribly far off from being able to screen someone and say, “Obesity is more likely to kill you than smoking.” Where then, because stopping smoking often causes weight gain, we might get to where smoking could extend a given person’s life.
Particularly in today’s society, the physical activity which comes with football -by far the sport most dedicated to off-season training (therefore physical activity is all year)- the mixture of weights and running -e.g. getting basketball players in the weight room is a pain in the ass- are going to be benefits we can’t just dismiss. But the slippery slope is readily apparent.
With alcohol, we don’t worry about our kids starting to drink and having issues with a glass of wine a night. We worry because we know opening the door to any alcohol includes opening the door to the potential of blackouts.
Politically, football, while it’s made a smart move in promoting its Play 60 campaign aimed at youth physical activity, is screwed. Individually, much like alcohol, there is no “do this and you’re golden” answer. Where longterm I’m confident football will diminish, but doubt it will die. At least not anytime soon. It will be more like MMA. 18 years old or younger doing it? Unlikely. Still able to do it as a professional? Sure. It’s either that or they make the game so safe it gets boring.
Meanwhile, I suppose a more practical takeaway is while I wouldn’t have my kid play football, I also wouldn’t demonize another parent who did. But I do raise an eyebrow at them.
Posted on October 23, 2017