As more research focuses on the damage concussions can cause, scientists now
report that even mild blows to the head might affect memory and thinking.
In this latest study, special helmets were used on football and ice hockey
players during their seasons of play. None of the players were diagnosed with a
concussion during the study period, but the special helmets recorded key data
whenever the players received milder blows to the head.
"The accelerometers in the helmets allowed us to count and quantify the
intensity and frequency of impacts," said study author Dr Tom McAllister. "We thought it might result in some interesting insights."
Repetitive brain impacts
The researchers found that the extent of change in the brain's white matter
was greater in those who performed worse than expected on tests of memory and
learning. White matter transports messages between different parts of the
"This suggests that concussion is not the only thing we need to pay
attention to," said McAllister, chairman of the department of psychiatry
at the Indiana University School of Medicine. "These athletes didn't have
a concussion diagnosis in the year we studied them... and there is a subsample
of them who are perhaps more vulnerable to impact. We need to learn more about
how long these changes last and whether the changes are permanent."
The study was published online in the journal Neurology.
Concussions are mild traumatic brain injuries that occur from a sudden blow
to the head or body. Symptoms include headache, blurry vision and difficulty
sleeping or thinking clearly.
Research on repetitive brain impacts not associated with diagnosed
concussions is sparse and contradictory, the researchers said.
McAllister, who conducted the research while affiliated with Dartmouth
College, compared 80 concussion-free varsity football and ice hockey players
wearing specialised helmets to 79 athletes in non-contact sports. He evaluated
them before and after the season with brain scans and learning and memory
A total of 20% of the contact-sport players and 11% of the non-contact
athletes performed worse on a test of verbal learning and memory at the end of
the season, a decline expected in less than 7% of a normal population,
Those performing worse exhibited more changes in the corpus callosum region
of the brain a bundle of nerves connecting the left and right sides of the
brain than athletes who scored as predicted.
Dr Howard Derman, co-director of the Methodist Concussion Centre in Houston,
said he wasn't surprised by the findings. He said blows to the head without a
reported concussion might cause brain damage that doesn't produce symptoms.
Derman said future research on this topic would be illuminating if, with
specially equipped helmets, blood flow and pressure changes in the brain could
be measured during repetitive head blows.
"If you can document that there are changes to the brain and there
haven't been significant blows, it would be even more of a concern," he
said. "We have to assume there is some cumulative effect, with multiple
blows causing the problem. It's like bending a piece of plastic once nothing
happens. But if you do it 40 times, you break the plastic."
Visit the American Academy of Neurology for more on concussions.