Some hockey and football student-athletes may perform worse than expected on learning tests after a season of head impacts – even if they never suffer an actual concussion, a new study published today in Neurology suggests.
But overall, those players tended to have similar mental skills as runners and other non-contact athletes, researchers found.
The findings come amid increasing scrutiny of the National Football League and its lack of action to address concerns about the effects of head injuries in its players.
Two weeks ago, former San Diego Chargers star Junior Seau committed suicide after what some believe were years of depression stemming from multiple concussions he suffered as a player. That same week, 100 retired NFL players sued the league over head injuries.
Effects on thinking and memory
Still, many questions remain about the effect of concussions on thinking and memory – including whether or not repeated, less-severe blows to the head may also cause short-term or permanent damage.
Another new study out today in Science Translational Medicine, reported elsewhere today by Reuters, describes pathological evidence of otherwise "invisible" trauma effects in the brains of soldiers, young athletes, and mice.
In the Neurology paper, researchers say that before their seasons started, college hockey and football players were just as sharp mentally as their peers playing non-contact sports. But about one in five of the contact-sport athletes seemed to suffer some effects from a season's worth of head impacts.
"On balance its good news and it provides a little bit of reassurance relative to the huge concerns that have been raised," said the study's lead author, Dr Thomas McAllister, from the Geisel School of Medicine at Dartmouth in Lebanon, New Hampshire.
Hitting head is not good
But, he added, the study "raises the question of, is there a subgroup of people for whom hitting their head over and over again may not be a good thing?"
For their study, Dr McAllister and his colleagues recruited Division I varsity athletes at Dartmouth College, Brown University and Virginia Tech.
At the start and end of the athletic seasons, the researchers gave cognitive tests to 214 hockey and football players, as well as 45 athletes on non-contact sports teams – such as track, crew and skiing – for comparison.
The hockey and football players were outfitted with special helmets that recorded data on each of their head impacts, such as the head's acceleration after contact.
Over the course of the season, the helmets recorded an average of 469 head blows per athlete, a number that varied between one and over 2 000 impacts. No athletes who suffered a concussion during the course of the season were included in the analysis.
Genetic differences on players
In general, there was no difference in how well contact and non-contact athletes performed on the series of thinking and memory tests – either before their seasons started or after they ended.
But on one learning test, taken by a smaller group of 100 athletes, 22% of hockey and football players had worse-than-expected postseason scores, based on their own preseason performance, compared to only 4% of runners, rowers and skiers.
"What we don't know is how long these poorer-than-predicted people stayed in that category," Dr McAllister told Reuters Health. "It may be that if we tested them six months later, it was fine."
Dr McAllister also pointed out that there wasn't a clear link between the number of times athletes got hit in the head, or how hard, and how they did on the postseason tests. So it may be that genetic differences between players affect how their mind and body respond to those repeated blows.
Impact measurement tools are being developed
One concussion researcher not involved in the new study agreed the findings are reassuring, but cautioned against athletes, parents and coaches becoming complacent as a result.
"What we don't want is for athletes to say, 'Unless I have a concussion, I don't have to worry about cognitive impairment,'" said Dr Paul Comper, from the University of Toronto.
He added that the tools used to measure head impacts are still being developed – and it's possible the helmets in the study weren't recording all of the relevant measurements that could link hits to thinking and memory.
Some of the researchers reported a financial interest in the helmet technology.
The study is a "good starting point," but calls for more research on the effects of repetitive head impacts, Dr Comper said.
"Just because we have these neurocognitive measures and you do well on them, doesn't mean you don't have brain damage," he told Reuters Health.
"We don't want to give people a false sense of security."
(Genevra Pittman, Reuters Health, May 2012)
A fatal blow to the brain