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Early Exposure to Tackle Football May Increase Risk of Brain Trauma Later

Former National Football League players who began to play tackle football before the age of 12 appeared to have an increased risk of later-life brain trauma, according to a study recently published online in the Journal of Neurotrauma.

Researchers from the Boston University School of Medicine and Brigham and Women's Hospital examined the brains of 40 former National Football League players using diffusion tensor imaging (DTI) to gauge the impact of early exposure to football on their brains. Half of the men, currently aged 40-65, began playing football before the age of 12, while the other half started at age 12 or later.

The researchers examined each former player's corpus callosum, which is a band of neural fibers that connects the two hemispheres of the brain. They sought to determine whether water molecules within the white matter of the corpus callosum would diffuse along one direction (as they should) or whether there would be multidirectional movement, suggesting damage to certain regions of the brain. Previous research has found altered diffusivity to be common following a mild traumatic brain injury.

The study authors used a few different measures to gauge whether the players were experiencing altered diffusivity, including fractional anisotropy and radial diffusivity. They expected to see more altered diffusivity, particularly in the anterior and posterior regions of the corpus callosum, in the under-12 group compared to the 12-and-over group.  

Their hypothesis turned out to be correct. After adjusting for duration of play, the authors discovered the under-12 group had "significantly lower fractional anisotropy" in three regions of the corpus callosum and higher radial diffusivity in one region of the anterior corpus callosum.

The findings suggest "incurring [repetitive head impacts] through tackle football play during a critical period of anterior [corpus callosum] growth before age 12 may disrupt developmental processes possibly resulting in lasting alterations in anterior [corpus callosum] white matter microstructure," the authors wrote. They noted that neurodevelopment may play a role in these findings, as fractional anisotropy "increases rapidly" in the corpus callosum prior to age 12, so repetitive head impacts "may disrupt the normal myelination process in childhood, possibly leading to a reduced peak level of myelination in the adult brain."

Before jumping to drastic conclusions, however, the study authors note that further research is needed on children to understand the long-term effects of repetitive head impacts have on developing brains. Additionally, these findings may not apply to athletes in other sports, such as ice hockey, soccer and lacrosse. They concede "replication of results is necessary before using these findings as rationale to implement significant rule or policy changes."

Though the study authors aren't willing to draw any sweeping conclusions, they believe their findings at least suggest there's reason to be cautious with youth-athletes under the age of 12.

"Regardless of the results of this study, it makes sense to me that children, that during those ages of around 10 to 12 whose brains are rapidly developing, shouldn't be hitting their heads over and over again," said lead researcher said Robert Stern, director of the Boston University Alzheimer's Disease and CTE Center's Clinical Core, to PBS Frontline. "This study supports that idea and suggests that there might be later in life consequences."

Earlier this year, the same group published a study in the journal Neurology that found former NFL players who began playing tackle football before the age of 12 fared worse as adults in terms of executive function, memory, and estimated verbal IQ compared to those who began playing at age 12 or later. Their latest study only bolsters the need for further research into the effects of repetitive head impacts at an early age. 

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