MONDAY, Nov. 26, 2018 (HealthDay News) -- High-impact hits may affect the brain development of children and teens after just one season of football, preliminary research suggests.
The study compared functional MRI scans taken pre- and post-season. The researchers saw more gray matter volume in those who had high-impact hits -- but no concussions -- over the season.
More gray matter indicates that the brain might not be working as well as it could be.
The brain contains an abundance of connections between nerve cells (synapses) that are constantly changing. New connections are made, while unused ones are pruned away. The process can be compared to tree trimming -- if you prune dead branches off a tree, it allows for healthy growth. The pruning that occurs in the brain also allows for healthy growth, the researchers said.
"The brain becomes more efficient after gray matter pruning," explained study author Gowtham Krishnan Murugesan.
The study included 60 youth and high school football players aged 9 to 18, said Murugesan, a research assistant in the radiology department at UT Southwestern Medical Center in Dallas. None had had a concussion or any known developmental, neurological or psychiatric disorders.
The players' high-tech helmets were outfitted with accelerometers -- sensors that measure the severity, location and direction of impacts to the head.
The researchers used information from the sensors to divide the group into high or low impact players. Twenty-four players were considered high-impact players, and 36 were low-impact.
In addition to looking at gray matter volume, the researchers also studied an area of the brain called the default mode network (DMN). This is a network of regions deep within the brain's gray matter. "The DMN network is important for planning and controlling social behaviors," Murugesan said.
The researchers saw a significant increase in power in this area for the high-impact group. Murugesan said that if gray matter pruning is happening as it should, the power should be reduced because the brain would be working more efficiently.
It isn't yet clear if the effects on gray matter are temporary. Murugesan said that after not playing for nine months (off-season), the players' brains may go back to what they were at the start of the season.
Dr. Bruce Silverman is a neurologist at Ascension Providence Hospital in Southfield, Mich. "In people who've had repeated head traumas -- measured by accelerometers -- brain pruning is not as effective," said Silverman, who wasn't involved in the study.
This study showed it doesn't necessarily take major knockouts or concussions to cause changes in the brain, he noted.
However, neither expert said it's time for kids to hang up their football gear. Any potential long-term effects aren't yet known.
In the meantime, Murugesan and his co-authors hope to make play safer. The data from the helmets suggested that a lot of the high-impact hits occurred during practice.
"Many players are getting more impact during practice," Murugesan said. One way to make play safer, he added, might be to replace some high-impact practice drills with low-impact ones.
Silverman agreed. "Practice could be a greater time of trauma than the game itself. In practice, players get pushed harder to be tougher for the game. The physical nature of practice may need to be toned down a bit," he said.
Also, part of the problem may be that players are faster now, he added.
"We've been making pads less encumbering," Silverman said. "In the past, you had something that slowed you down and didn't allow you to run as fast as the new equipment does."
Silverman said parents should make sure that young football players are well-equipped with helmets and pads. The coaching staff should be trained to monitor and evaluate kids after any type of head injury, and not put kids back into play too soon, he noted.
The study was scheduled for presentation Monday at the Radiological Society of North America meeting, in Chicago. Findings presented at meetings are typically viewed as preliminary until they're published in a peer-reviewed journal.
Learn more about head injuries in sports from the American Association of Neurological Surgeons.