This is in part a response to a thread a couple weeks back where I posted a link to the new study by Robert Stern and Julie Stamm et al in the journal Neurology that shows an apparent causal relationship between age of first exposure (AFE) to football and cognitive impairment in NFL players. The comments to the original thread hit a full spectrum that can be honed by a close reading of the study and past work on CTE. A few things have happened since that post that make this more interesting; the Super Bowl for one, John O’Korn transferring into Michigan for another and a civil lawsuit filed against the national office of Pop Warner football for the wrongful death of Joseph Cernach. I’m going to take a closer look at the actual data from the new study to refute some points made in the previous thread (including my own). Then, I’m going to apply this new data to previous studies and finally I will present my opinion as to where these and other recent events are leading.
First the latest CTE news story in which a suit has been brought in a federal court in Wisconsin against The Pop Warner Foundation stating that Pop Warner failed: to train coaches, to use safe helmets, to limit contact in practice, to teach players to use safety equipment and finally, failed to follow established concussion protocols dating back to 1997. The suit was filed by Debra Pyka, mother to Joseph Chernach who suffered from CTE having been diagnosed after he committed suicide at the age of 25 in June of 2012. Joseph played Pop Warner from the age of 11 in 1997 to 14 in 2000.
This is Joseph (a Michigan fan) with mom on the left and Joseph in happier times on the right. Photos are taken from Joseph's donor page at the Sports Legacy Institute (SLI) website and from photos supplied by the family to news outlets.
Fixed tissues from Joseph were examined by Ann McKee at the Boston University Center for the study of Traumatic Encephalopathy (CSTE.) His case was classified as stage 2 - possibly stage 3 and remarked as one of the worst for his age. Joseph’s complete brain was evidently not sent, preventing definitive staging.
This wasn’t the only suit filed in the last weeks but it got my attention and brought back the issues put forth by the CSTE study that came out on Jan 28th. It is important to grasp what that study is saying if only because we are likely to get many more lawsuits like the one above in the near term as well as a continued flight from youth football (participation already being down 29% since 2008.) But these are not the only reasons.
The study in question is entitled
Age of first exposure to football and later-life cognitive impairment in former NFL players
If you haven’t read it and are able to do so… just do it. It’s not that technical. Pundits in the media, however, and others continue to misconstrue its conclusions and validity which is another reason for this diary. What follows here is my understanding of the data presented with sincerity if not authority. It’s clear from the comments to the original board post that many were interested in the work but didn’t have the time to research the journal article.
The study is a cross sectional analysis for causal factors to explain actual cognitive impairment found in a sample of NFL players. The researchers pulled only from those players who were known already to exhibit cognitive, behavioral or mood symptoms in the 6 month period prior to participating. That is what a cross-sectional study is – a cross section of a population. There is no control group. A control is not needed for this sort of examination.
The subjects were pulled from a group of about 150 players who were vetted so as not to have any previous central nervous system (CNS)disorders (no Parkinson's, Alzheimer's, epilepsy or any other incoming disorder.) That cuts out quite a few.
The remaining subjects were then paired by similar age and different AFE to FB (one <12 the other >=12.) Current 10 year old (y.o.) FB players get different coaching and different equipment than 50 y.o. ex-FB players did 40 years ago. This pairing controls for the era of football – as the game has evolved year to year since it was first played but specifically in the living history of the NFL players in the study. The older players did not have as much opportunity to play youth football which further limited the possible pairs.
After all the selection is done only 42 players remained in the study population, 21 in each AFE group. There has been much talk about what exactly you can determine from a sample size of only 42 players. Well it turns out you can do quite a bit. Below is the breakdown of the demographics in the study taken from the article.
Looking over the demographics AFE to FB is the primary discriminate along with lesser but significant difference in duration of play(DOP). The confounding nature of DOP and AFE is a valid caveat to any conclusion drawn from this cross section of subjects. Maybe instead of the AFE it is the total number of hits taken that determines later life cognitive impairment. DOP (and age – which is not confounded due to the paired experiment design) was however accounted for and adjusted for in the analysis to focus on AFE.
Three tests were chosen for the analysis (given their focus on the theoretical cognitive deficits expected in CTE) and these were summarized in 9 scores. These are below in unadjusted and adjusted form in the exact data tables published in the journal Neurology.
All the tests are significantly lower for the AFE <12 group. While any significance is interesting, all of the measured outcomes being significant and lower is even more so. Yes, there are only 21 players in each group, but the significance of each of these scores is very high. Suppose you flipped a coin nine times and it came up heads all nine times… you would look at the other side of the coin wouldn’t you? Suppose it came up heads 189 times. That is all this preliminary study is saying. Youth football is a factor in the type of cognitive impairment associated with CTE in NFL players.
In retrospect this confirms a previous study on CTE in December of 2012 done by Ann McKee and Robert Cantu et al though the age of first exposure to the repetitive head injury was not suggested there. Let me suggest that now. That study was appropriately entitled
The spectrum of disease in chronic traumatic encephalopathy
The study included 85 recently deceased subjects known to have suffered repetitive mild traumatic brain injury (mTBI) along with a control group of 17 subjects with no history of the mTBI. The brains of these subjects were donated to the study for neuropathological evaluation along with an independent and blind parallel series of post mortem interviews with next of kin to determine case history.
68 of the 85 subjects showed signs of CTE(80%), while 51 of the 85 subjects were diagnosed with CTE exclusively(60%.)
From the pathology a staging system is laid out to which the behavior and historical data are spliced. Part of this historical data is the age at time of death. I took the liberty to put that into an excel table below.
Here is the same data graphically represented next to the iconic images of the staging done by Ann McKee in this study.
What hadn’t occurred to me (and isn’t done in McKee’s analysis either for that matter) was to take this age at time of death data and extrapolate back to stage 0 which given the progressive model for the disease would be the time the CTE started.
Here’s the same data with a linear regression.
Admittedly this is an N of 51 and only 33 of these are NFL players. The implication, however, is that CTE started at age 11 and 3/4 years old on average. This is a possible reason for the new study in the first place.
All the studies are calling out for more longitudinal designs to be funded and carried out. That would be about right if two sorts of people were doing the calling out. One would be the scientific sort who are careful with their claims and mindful of their funding. The other sort would be the watchdogs of the sport. That would be the NFL executives and owners.
For the rest of us these cross sectional studies will do just fine. There is no way I would ever ever let my son play the game of football as long as he was a minor in my charge. You don’t need broad based studies to find cause. It wouldn’t take too much convincing if he showed resistance.
There is obviously much more to these studies than I’m relating here. I encourage you to look for yourself to ferret out the details you might be interested in.
Cherry picking studies and data from science journals is a good way to get off base and picked off on a college football blog. I do want to present this table however, again from McKee and Cantu’s spectrum snapshot in 2012.
This is tying together the case histories (gathered by Robert Stern who is another author of the Spectrum paper.) From this chart you can begin to get a clinical take on what the progression of this disease is like. I’m showing this because there were some people who responded with either denial, disdain or ignorance to the dangers here.
This is from the FAQ at BU CSTE
The symptoms of CTE include memory loss, confusion, impaired judgment, impulse control problems, aggression, depression, anxiety, suicidality, parkinsonism, and, eventually, progressive dementia. These symptoms often begin years or even decades after the last brain trauma or end of active athletic involvement.
Roger Goodell in the many interviews from Super Bowl week was happy to point out that hits to defenseless players are down 68% in 2014 (yes they track that), concussions were down 25% and that concussions in the past three years have dropped from 173 a season to 111. I doubt they track or could track the sub-concussive blows that are likely the true culprit in CTE.
Still we got the Edelman hit with 11 minutes to play in the 4th with no concussion protocol or independent review during or after the game. It’s going to be impossible to take the football out of football no matter how much you deflate it.
This has already gone too long. I’ll save you my thoughts on where we’re going from here. But I do think Harbaugh took O’Korn and Oregon took Adams for reasons that aren’t entirely unrelated. You can’t have enough QBs in the games to come.