With the NFL preseason in full swing, I can’t help thinking about the incremental neurological damage that’s being inflicted on the players with each vicious tackle and violent collision. The damage — chronic traumatic encephalopathy, the degenerative brain disease better known as CTE — has often been decades in the making.

Chris Nowinski, the former professional wrestler-turned-neuroscientist who now runs the Concussion and CTE Foundation, knows the grim arithmetic only too well. He observes that the risk of developing CTE appears to climb with every additional season of football played, and among the hundreds of former players that Boston University scientists have examined, more than half of those who played twelve seasons or longer turned out to have the disease.