CTE in a soccer player with no history of concussion

Football/Soccer/Scientist friends,

This is a landmark study (see Grinberg et al. (2016). It shows the confirmation of chronic traumatic encephalopathy (CTE) in the post-mortem brain of a soccer player WITHOUT any history of concussion. By the way, the player (though he isn't named) is almost certainly Hilderado Bellini - a legend of the game. Bellini won the world cup with Brazil and played for some of the premier Brazilian clubs of his time.

The no-history of concussion is important, b/c it supports the idea that subconcussive impacts in soccer may be sufficient to produce CTE. And, honestly, as an aficionado of the beautiful game, this is somewhat troubling.

Why is it troubling? Because for the longest time, I (and many) assumed that CTE would rear it's ugly head in the world of soccer, and while there have been some reports of possible CTE in soccer players (see Hales et al. (2014) , this is the first (to my knowledge) which highlights the history of no-concussion.

There are caveats to over-interpreting this study-

1. This gentleman was playing soccer in the 50s - a time where diagnosing concussions wasn't the norm. Therefore, it is entirely possible that he did experience concussions - but were never diagnosed.

2. This is one anecdotal report. It's possible that his CTE is independent of his history as a soccer player and that his CTE was consequential of some other genetic/environmental effect.

Why is this study relevant to soccer?
Subconcussive injuries are asymptomatic. Therefore, they pose a greater risk to athletes than concussions because they are impossible to diagnose. If the link between subconcussive injuries and soccer is confirmed, perhaps we need to have a serious discussion about heading.

Do we know for sure that heading leads to subconcussive injuries?
No, far from it. There's little evidence for it, except this one study that suggests that heading in amateur soccer players leads to abnormal white matter (the stuff that allows brain cells to send messages to each other) restructuring ( see Lipton et al. (2013)). But, this is far from confirmation of the above.

It is interesting to note that Bellini was a central defender - a position which involves the most heading in a game (I don't have data to support this, but, it would be fairly obvious to anyone that plays/watches soccer). Therefore, the repeated subconcussive injury issue is consistent with what we might expect.

As more and more soccer players donate their brains to science, I expect us to see an increase in CTE diagnosis. With the suicides of Robert Enke and Gary Speed - two well known, high profile, footballers, the interest in CTE was always going to rise.

I'm not sure what the long-term impact will be on soccer. But, we are at the beginning stages of raising awareness for what might be an insidious beast preying upon our beloved soccer-playing heroes.

Pubmed link: Link to original study

Artificial turf and soccer

Before I start writing out whether or not playing soccer on artificial turf (AT) leads to injury, I have to admit that this was a real learning experience for me. For years, I've been convinced that playing on turf leads to higher chances for injury. So much so, that I repeated that on at least three radio shows last summer, during the women's World Cup.

But, that's why I love science. It proves me wrong all the time, and reminds me about how little I really know. It's humbling, wondrous and informative.

Just like my recent blog post on heading and youth soccer, I will be linking to the abstract of various articles. If you would like access to a particular paper in it's entirety, tweet me at @AlzBlog101 and I would be happy to send it to you.

1. What is Artificial Turf (AT)?

It's a playing surface used for sports such as field hockey, soccer, american football, etc. AT is made of synthetic fibers that look like grass. However, for countries where maintenance of natural grass is problematic due to non-ideal temperatures, AT has proven to be an alternative.

2. How did the idea that AT leads to increase in soccer injuries start?

While there were probably anecdotal reports, the first study that examined this issue was Arnason et al. (1996) . They found that the propensity for injury increased on AT vs natural grass.

3. Were the Arnason results replicated by other studies?

No. There have been many studies that suggest that there is no difference between injury risk of AT vs natural grass. These can be found here --- Ekstrand et al. (2006), Steffen et al. (2007), Fuller et al. (2007), Aoki et al. (2010), Bjorneboe et al. (2010), Kristenson et al. (2013) .

In essence, almost all studies suggest that the risk for injury does not increase for athletes playing on artificial turf. It's important to note that the studies cited above cover the gamut from NCAA soccer players to professional footballers - both male and female. So, there isn't a bias in terms of the level that the game is being played.

Here's something even more surprising. There have been studies that suggest that playing on artificial grass may be linked to LOWER injury rates than natural grass. Those can be found here --- Ekstrand et al. (2006), Soligard et al. (2012), Williams et al. (2013), Almutawa et al. (2014), Meyers (2013).

4. Okay, so playing soccer on AT is better than on natural grass?

Not so fast. You see, the articles cited above look at injuries as a whole. It's still possible that there are differences in particular injuries. A good analogy is that the articles above are looking at the injury issue at a whole-forest level. Whereas, in order to understand the risk for specific injuries, we have to go down to the tree-level.

5. Have there been studies that look at specific injuries in terms of artificial turf?

Yes.

6. What did they find?

The big one is that AT seems to be bad news bears for your ankle! Ekstrand et al. (2006), Steffen et al. (2007), Ekstrand et al. (2011) all found that playing on AT leads to an increase in ankle injuries in soccer players. For the sake of completion, it is important to note that Soligard et al. (2012) found the opposite - a reduction in ankle injury in soccer players playing on AT.

Hagglund et al. (2011) found that there was no difference between AT and natural grass surface for risk of patellar tendinitis (that's a fancy way of saying pain caused by inflammation in the knee).

Ekstrand et al. (2011) found that male soccer players were less likely to have a quad injury when playing on AT vs natural grass.

7. Woah! Getting too much. Summarize this for me.

Essentially, there is no increase in overall risk for injuries when playing on artificial turf vs natural grass; in fact, some studies suggest that it may be better overall than grass. However, there's general consensus that playing on AT may be a risk factor for ankle injuries, in particular. So, watch those ankles, friends!

8. So why does this myth about AT persist?

There are some general reasons - such as the naturalistic fallacy - where people believe that just because something is natural, it is automatically better than something synthetic or artificially manufactured.

Another reason is that we tend to extrapolate results from other sports into soccer. A perfect example of this is comparing football injuries to soccer. Both can be played on AT and therefore, when we see a study that suggests that injury X is increased in football, we assume incidence of injury X is also increased in soccer.

However, the sports are drastically difference and this assumption isn't necessarily true. For example, Balazs (2015) performed an examination of the literature, and found that playing on AT results in an increased risk for anterior-cruciate ligament (ACL) injuries in american football, but not soccer players. Therefore we should be careful to not over-interpret data seen in other sports played on AT.



So, lesson learned from my perspective - always fact-check everything. Especially things that I "know" are true.