It is Topic No. 1 in football.
Not just in the NFL, but at every level, the concussion discussion is all the rage.
And you really have to wonder what took so long.
What most of us have suspected for decades has come to the forefront in the last few years, that an inordinate number of ex-players in their 40s and 50s are living with dementia, Parkinson's and all manner of head-related difficulties, and dying young of Alzheimer's or Lou Gehrig's disease.
In a study of more than 3,400 retired NFL players released last week, government researchers found the death rate from those two brain diseases four times higher than among the general U.S. population.
While the lead researcher said he could not establish cause and effect with concussions, numerous studies in recent years have done precisely that.
What we do not know is why it affects Dave Duerson one way and Gary Fencik another.
Duerson deteriorated so quickly, yet hard-hitting teammate Fencik still sounds and acts like the same kid who came out of Yale 36 years ago.
What we do not is why NHL enforcers such as Wade Belak (age 35), Derek Boogaard (28) and Rick Rypien (27) all died in the summer of 2011 from issues related to their NHL careers, yet Keith Magnuson -- who probably took as many punches as anyone ever has in hockey -- was as sharp as a 20-year-old at 56, before his death in a car accident while a passenger in 2003.
What we do not know is why Muhammad Ali is as he is, yet Lennox Lewis at 47 speaks the King's English as properly as he did -- perhaps even better -- than when he became a professional boxer.
What we absolutely do know is that getting hit in the head repeatedly is bad, something your mother probably ingrained in you by the time you were 10.
But there's absolutely no understanding of why it doesn't impact some as much as others.
Paul Konerko and Sidney Crosby looked like they took the same elbow to the head, but Konerko was back in a week and Crosby played eight games in 14 months.
Was it the second hit in back-to-back games that really did the most damage to Crosby's brain? Was he more vulnerable because he already was concussed? Was he still concussed? Does he have a softer skull or more room for his brain to rattle?
Brent Seabrook has had several concussions the last few years. Some have looked really bad (Raffi Torres) and others not nearly as damaging (James Wisniewski).
Is Seabrook more prone to them because of the construction of his head? And why is he able to recover more quickly than most, sometimes within a few days or even hours?
Why was Jonathan Toews able to play four-plus games after suffering the hit that caused a concussion last season, before the symptoms got so bad that he had to admit the injury and miss 22 games?
Was it one hit Jim McMahon took that landed him where he is now, on the cover of Sports Illustrated with early-onset dementia? Was it a career filled with devastating blows? Or was it that one game in Minnesota late in his career when he was hit a dozen times in one game so violently that you had to change the channel?
Would he have lived a relatively normal, post-career life if not for that one horrific game, just as many suspect Ali suffered his life-defining injuries in the Thrilla in Manila?
Or was this their destiny because of their specific craniums?
Clearly, what medical science doesn't know is many times what it does know.
Still, hockey and football are taking seriously the problem and doing more to make the game safer while not removing the physical contact that makes their athletes rich, their sports entertaining and their networks eager to pay billions.
They will continue to try, knowing they will never make it completely safe, so players will continue to play and retired players will continue to file lawsuits.
Not long ago, a reader wondered via email whether he could even enjoy the NFL anymore, calling every player "a walking lawsuit," and thinking he could no longer appreciate the game because he saw every play as a potential court case.
It's fair to ponder, certainly, but most fans take the approach that players are compensated quite well to take the risks associated with playing such a violent sport.
And while many talented, young athletes look to baseball, basketball and golf as a way to keep their brains intact, disadvantaged players with no other option will continue in football as the only way out of a hopeless upbringing.
There will always be an NFL because there will always be that dream of wealth, just as there will always be an NHL because it remains every Canadian kid's dream to drink from the Stanley Cup.
These games will continue to carry a risk. For inexplicable reasons, the risk will be greater for some than others.
This, unfortunately, is also nothing new.
•Listen to Barry Rozner from 9 a.m. to noon Sundays on the Score's "Hit and Run" show at WSCR 670-AM, and follow him @BarryRozner on Twitter.