Even single season of football may disrupt brain development in youth

According to Gowtham Krishnan Murugesan, research assistant in the Department of Radiology at UT Southwestern Medical Center in Dallas, Texas, this research demonstrates that playing a season of contact sports may affect normal grey matter pruning in high school and youth football players.

The brain is highly complex with an abundance of neural connections. Through a process called pruning new connections are formed, and unused connections fall away. This process is necessary for healthy brain development just like cutting back unnecessary or dead branches keep a tree healthy and helps in its growth.

"Pruning is an essential part of brain development, by getting rid of the synapses that are no longer used, the brain becomes more efficient with aging, said Murugesan.

The researchers conducted this study to determine whether exposure to repetitive head impacts affects brain pruning in the young football players.

For the purpose, 60 youth and high school football players were outfitted with the Head Impact Telemetry System (HITS). The players had no history of developmental, neurological or psychiatric abnormalities and no history of concussion prior to or during the season. HITS helmets are lined with sensors or accelerometers that measure the magnitude, location and direction of impacts to the head. Impact data from the helmets were used to calculate a risk of concussion exposure for each player.

Players were then split into the groups of low-impact players (36) and high-impact players, based on each player's risk of cumulative head impact exposure as determined by HITS. Pre- and post-season resting state functional (fMRI) scans were performed on all players, and changes in power within five components the default mode network (DMN) were analyzed.

The DMN is a network of regions deep in the gray matter areas of the brain. It includes structures that activate when a person is awake and engaging in introspection or processing emotions, which are activities that are important for brain health.

There was a significant increase in power and gray matter volume in the frontal DMN in the high-impact group, showed post-season results.

"Disruption in normal pruning has been shown to be related to weaker connections between different parts of the brain. Our study has found a significant decrease in gray matter pruning in the frontal default mode network, which is involved in higher cognitive functions, such as the planning and controlling of social behaviors, said Murugesan.

Studies of biomechanical data from this same group of participants were conducted at Wake Forest University in Winston-Salem, N.C. Their findings showed that most head impacts occurred during practice.

"By replacing high-impact practice drills with low- or no-impact drills, the overall head-impact exposure for players can be reduced," Murugesan said.

The minor modifications to the game could also be implemented to reduce full-speed contact, suggested the authors.

"The new National Football League kickoff rule eliminating the running start is an example," Murugesan said.

The researchers hope to conduct further study to fully understand the long-term changes in resting state brain networks and their association with neuropsychological task performance.