After just one season, youth football players with greater head impact exposure showed changes to white matter of the brain.
It is estimated that around 30 million children and adolescents in the United States take part in some form of sports.
While such participation has clear health benefits, the risks cannot be overlooked; each year in the U.S., more than 3.5 million injuries are incurred through youth sports, with the majority occurring in contact sports - such as football.
Among the most serious injuries are those to the head; according to the Centers for Disease Control and Prevention (CDC), in 2009, almost 250,000 children and adolescents were admitted to emergency departments as a result of sports-related injuries that involved traumatic brain injury (TBI) or concussion.
A number of studies have documented the effects concussion can have on the brain; a study reported by Medical News Today, for example, showed that concussion can lead to changes in the brain's white matter that persist for at least 6 months.
Assessing the brain effects of non-concussion head impact
However, Dr. Christopher T. Whitlow - lead author of the new study and associate professor and chief of neuroradiology at Wake Forest School of Medicine in Winston-Salem, NC - notes that in relation to youth sports, few researchers have investigated the brain effects of head impact that does not result in a concussion diagnosis.
"Most investigators believe that concussions are bad for the brain, but what about the hundreds of head impacts during a season of football that don't lead to a clinically diagnosed concussion?," asks Dr. Whitlow. "We wanted to see if cumulative sub-concussive head impacts have any effects on the developing brain."
For their study - published in the journal Radiology - Dr. Whitlow and team enrolled 25 male youth football players aged 8-13 years.
Using data from the Head Impact Telemetry System (HITs) - software that monitors the frequency and severity of head impacts in sports - the researchers tracked the cumulative exposure to head impacts among the participants over one football season.
In order to confirm the accuracy of this data, the team recorded and assessed every game and practice session of the season.
Greater head impact exposure linked to changes in white matter
Before and after the football season, each player underwent diffusion tensor imaging (DTI) of the brain - a form of advanced magnetic resonance imaging (MRI) that can identify small changes to the structure of white matter.
Specifically, the team looked at fractional anisotropy (FA) measurements - the movement of water molecules along nerve fibers in the brain called axons.
The researchers explain that in healthy white matter, FA is high, representing a more uniform water movement. In some studies, irregular water movement has been associated with reduced FA and brain abnormalities.
In their analysis, Dr. Whitlow and team found that the youths who had experienced higher cumulative head impact exposure showed reduced FA in certain areas of the brain, compared with those who had low exposure to head impacts.
"These decreases in FA caught our attention, because similar changes in FA have been reported in the setting of mild TBI," notes Dr. Whitlow.
Importantly, the team point outs that none of the players had signs or symptoms of concussion.
While the researchers say they are unable to conclude whether the reduced FA observed in the study is representative of functional brain changes or long-term abnormalities, their findings warrant further investigation.
"Football is a physical sport, and players may have many physical changes after a season of play that completely resolve. These changes in the brain may also simply resolve with little consequence. However, more research is needed to understand the meaning of these changes to the long-term health of our youngest athletes."
Dr. Christopher T. Whitlow