In light of the discussion started this morning, some have pointed out that examining Chris Henry's case and trying to interpolate conclusions from it is necessarily bad science and logic. That's fair, though such a response is often made to discourage further thought about the subject, which is not fair.
But in the interest of furthering the dialogue, it would behoove us all to know that Henry's chronic traumatic encephalopathy (CTE) is not, in fact, one isolated incident. As Malcolm Gladwell reported last year (amid an intriguing but ultimately specious comparison between the NFL and dogfighting), the researchers working on finding evidence of CTE in deceased athletes have a larger sample size, and the initial returns are not promising:
[Bedford, MA Veterans Hospital director of neuropathology Ann McKee] has now examined the brains of sixteen ex-athletes, most of them ex-football players. Some had long careers and some played only in college. Some died of dementia. Some died of unrelated causes. Some were old. Some were young. Most were linemen or linebackers, although there was one wide receiver. In one case, a man who had been a linebacker for sixteen years, you could see, without the aid of magnification, that there was trouble: there was a shiny tan layer of scar tissue, right on the surface of the frontal lobe, where the brain had repeatedly slammed into the skull. It was the kind of scar you’d get only if you used your head as a battering ram. You could also see that some of the openings in the brain were larger than you’d expect, as if the surrounding tissue had died and shrunk away. In other cases, everything seemed entirely normal until you looked under the microscope and saw the brown ribbons of tau. But all sixteen of the ex-athlete brains that McKee had examined—those of the two boxers, plus the ones that Nowinski had found for her—had something in common: every one had abnormal tau.
Of note: the tau here, as mentioned before, is a protein that inhibits brain function, and is primarily seen in Alzheimer's patients and victims of other similar dementia. It was also prominently present in Chris Henry's brain tissue study. More:
The other major researcher looking at athletes and C.T.E. is the neuropathologist Bennet Omalu. He diagnosed the first known case of C.T.E. in an ex-N.F.L. player back in September of 2002, when he autopsied the former Pittsburgh Steelers center Mike Webster. He also found C.T.E. in the former Philadelphia Eagles defensive back Andre Waters, and in the former Steelers linemen Terry Long and Justin Strzelczyk, the latter of whom was killed when he drove the wrong way down a freeway and crashed his car, at ninety miles per hour, into a tank truck. Omalu has only once failed to find C.T.E. in a professional football player, and that was a twenty-four-year-old running back who had played in the N.F.L. for only two years.
The last player mentioned is almost certainly Fred Lane, the 24-year-old Carolina tailback who was shot to death by his wife before his 3rd year of play. In a particularly wry case of irony, Lane's Wikipedia picture shows him taking a helmet-to-helmet hit that pops Lane's hat off. But his scan came back clean, so it's not as if one bad hit like that is all it takes. The effects, again, are likely cumulative.
It's also worth mentioning that these researchers have generally depended on families offering the brains to the researchers, with the help of sports activist Chris Nowinski. So families who never saw any evidence of brain damage could have lacked the motivation to send a recently passed loved one's brain off for testing.
Further, as football is, for the most part, a relatively new sport, many of its former players are still alive, if aging. Those that have healthily lived into their 70s, 80s, and beyond are likely free of serious neurological side effects that would have manifested long before now. So their health ironically drives the percentage of known CTE sufferers higher, since the Tau proteins can only be discovered upon autopsy.
And yet, that minimum of 20 players that had been tested when this article was written exhibit what's starting to look like a consistent pattern, regardless of their age at death. It's still too early to draw conclusions without mountains of more data, but it's also too late to call Chris Henry's early onset of CTE an isolated incident.