For more than a decade, researchers trying to make sense of the mysterious degenerative brain disease afflicting football players and other contact-sport athletes have focused on the threat posed by concussions. But new research suggests that attention was misguided.
Instead of concerning themselves with the dramatic collisions that cause players to become dizzy, disoriented or even lose consciousness, neuroscientists should be paying attention to the routine hits to the head, according to a study that examines the root cause of chronic traumatic encephalopathy, better known as CTE.
"On the football field, we're paying attention to the bright, shiny object -- concussion -- because it's obvious," said Dr. Lee E. Goldstein of Boston University, who led the study published Thursday in the journal Brain. But, he continued, "its hits to the head that cause CTE."
The disease is marked by abnormal deposits of calcium and proteins throughout the brain, as well as by neuropsychiatric symptoms that range from tremors and memory problems to depression and suicidal rage. For now, the only way to diagnose it is by examining a patient's brain tissue after death.
Some of the hits that cause CTE may result in concussion, Goldstein said. But his team's findings show that concussion is not necessary to trigger the process.
Indeed, the new research suggests that concussion and CTE are completely different medical problems.
In mice, head impacts that caused concussion and those that led to CTE had different effects inside the brain. In people, the symptoms tend to show up as different behaviors that became evident at very different times. In mice, the research documented immediate behavioral responses to head impact that ranged from zero to disability. And researchers captured what appeared to be the earliest moments of CTE in many mice that showed few if any immediate symptoms.
That new research underscores that the kinds of "sub-concussive" blows to the head that many athletes routinely endure are far more worrisome than players, their parents and their physicians have been led to believe.
Even as football programs from Pop Warner to the National Football League are adjusting their rules to reduce concussions, the findings suggest these efforts will not be enough to prevent long-term injury.
"You have to prevent head impact," Goldstein said.