I have been a fan of professional football since my college days (go Pats) but I also recognize that it is a brutal sport prone to injuries. In recent years awareness of the true neurological risk of concussions, especially repeated concussions, has been increasingly coming to light. This may cause some cognitive dissonance among fans, players, and anyone involved with the NFL, including broadcasters.

Recently Fox News published and article in which Dylan Gwinn writes:

Don’t look now, but concussions have become the new global warming: a debate where “consensus” trumps evidence, and heroes and villains are determined by their stances on an issue where the science is bogus at worst and murky at best.

This is classic FUD – fear, uncertainty, and doubt, the primary tactic of those who find reality not to their liking in some particular aspect.

Gwinn creates the classic false dichotomy between consensus and evidence. What if the consensus is based upon scientific evidence, and in fact the consensus of experts is the best way for non-experts to understand what the evidence actually says.

Further, all science is murky, at least to some degree. The clarity of a scientific conclusion exists along a spectrum from genuinely controversial to rock solid, but scientific evidence is always complex, subject to multiple interpretations, and incomplete. It doesn’t take much creativity to portray any scientific conclusion (even those at the rock solid end of the spectrum) as murky. Creationists are evidence of that.

Gwinn also does not address another issue at the core of this debate – the precautionary principle. This is the notion that it is best to err on the side of caution regarding a potential harm when the science is still preliminary. Application of the precautionary principle is admittedly complex and is easily abused. I write often about abuse of the precautionary principle when it comes to vaccines, GMO, and unnamed “toxins.” I also write about ignoring the precautionary principle when it comes to things like global warming, and now concussions from playing contact sports. These represent opposite extremes, when the reasonable position is somewhere in the middle, with Aristotle’s golden mean.

Abuse of the precautionary principle generally takes the form of overhyping possible risks, cherry picking evidence suggesting risk, ignoring, dismissing, or downplaying evidence of safety, and demanding unreasonable assurances of “zero risk.”

Ignoring the precautionary principle usually takes the form of FUD – we don’t know everything, so let’s act as if we know nothing and ignore potential risks. Until you can prove beyond doubt that the risk is real, we should not take any steps to mitigate it, even if by the time the risk is certain it will be too late.

There is no simple algorithm to calibrate where an issue lies along this spectrum. It takes a working knowledge of the science along with a fair and nuanced evaluation of all the relevant issues. Personally I have absolutely no idea if the planet is warming due to human activity. By this I mean that I am not competent to look at the raw data and meaningfully evaluate it while putting it into the context of a thorough understanding of climatology. That is because I am not a climatologist, and the kinds of data they deal with are not really accessible to a non-expert. I am dependent on the consensus of expert opinion. I can decide if their arguments make general scientific sense, and which side seems to have the last word when specific points are thoroughly debated.

With concussions I have a much better personal handle on the science. I am a neurologist. I treat patients with concussions, some from sports injuries. I can read the primary literature and understand it. With regard to concussions and sports the consensus has shifted over recent years to be far more cautious in returning players to the field. This is based upon studies showing that the risk of a second concussion is greater in those who have suffered a first concussion, and the damage is also more severe and longer lasting. The current recommendations are for a player to be symptom free before returning to play following a concussion.

We are also gathering more evidence about the long term neurological effects of repeated concussions over a career. A recent examination of retired NFL players found:

The retired players’ ages averaged 45.6 ± 8.9 years (range, 30-60 years), and they had 6.8 ± 3.2 years (maximum, 14 years) of NFL play. They reported 6.9 ± 6.2 concussions (maximum, 25) in the NFL. The majority of retired players had normal clinical mental status and central nervous system (CNS) neurological examinations. Four players (9%) had microbleeds in brain parenchyma identified in SWI, and 3 (7%) had a large cavum septum pellucidum with brain atrophy. The number of concussions/dings was associated with abnormal results in SWI and DTI. Neuropsychological testing revealed isolated impairments in 11 players (24%), but none had dementia. Nine players (20%) endorsed symptoms of moderate or severe depression on the BDI and/or met criteria for depression on PHQ; however, none had dementia, dysarthria, parkinsonism, or cerebellar dysfunction. The number of football-related concussions was associated with isolated abnormalities on the clinical neurological examination, suggesting CNS dysfunction. The APOE4 allele was present in 38% of the players, a larger number than would be expected in the general male population (23%-26%).

The concern is that repeated brain trauma causes chronic neurodegenerative disease over time. The above study finds evidence of chronic damage in a substantial minority of retired players. A 2015 review of the literature on chronic traumatic encephalopathy found:

We found that a history of mTBI was the only risk factor consistently associated with CTE.

But also:

Our review reveals significant limitations of the current CTE case reporting and questions the widespread existence of CTE in contact sports.

What both these recent reviews find, essentially, is that there is evidence of chronic neurological damage in professional athletes correlating with concussions, but that chronic injury is not widespread and exists in a minority of players. You can focus on either the positive or negative aspects of this data – on the fact that there is evidence of neurological injury in some players, or on the fact that injury is only present in a minority of players. Everyone agrees we need further research.

How do we apply the precautionary principle to this incomplete scientific data? As with global warming, those who wish to deny that there is any problem are likely to argue against the strawman of the most extreme solution, such as banning all contact sports. Often reasonable measures that are proportional to the evidence and the potential risk are ignored.

With global warming, for example deniers warn of a government take over of entire industries, and degrading civilization to a hippie paradise without electricity and automobiles. How about just investing in greater energy efficiency and renewable sources. Those are win-wins, whatever you think about global climate change.

With regard to contact sports and concussions there are also reasonable measures that can be and are being taken short of a total ban on high-risk sports. Recommendations are already moving in this direction – players should not return to play the day of a concussion, and they need a longer period of recovery before returning to play. Certain styles of play are more dangerous than others, and so rules can be tweaked to minimize risk (as they always have been). Incremental improvements in equipment can also reduce player injury.

Making contact sports safer for players is a no-brainer. We now have more information about concussions to inform efforts to make contact sport safer.

Gwinn is right about one thing – concussions in sports is the new global warming, just not in the way he intended. There is emerging science indicating a risk. The science has not all been worked out yet, but the signal of a risk of neurological injury is there, and is also quite plausible. At the very least we should be taking reasonable measures to minimize injury. This situation is fairly analogous to global warming in the context of risk management.

In both cases the evidence supports taking reasonable measures to mitigate risk. In both cases deniers are engaging in FUD to argue that we should do nothing.