It may only take one season of high school football cause microscopic changes in the structure of the teen-aged brain, according to researchers who say their study adds to evidence that repeated blows to the head may lead to cognitive disorders later in life, even when the injuries are not serious enough to cause a concussion.
“It is becoming pretty clear that repetitive impacts to the head, even over a short period of time, can cause changes in the brain,” said study senior author Chunlei Liu, a professor of electrical engineering and computer sciences and a member of the Helen Wills Neuroscience Institute at the University of California, Berkeley.
“This is the period when the brain is still developing, when it is not mature yet, so there are many critical biological processes going on, and it is unknown how these changes that we observe can affect how the brain matures and develops,” Liu said in a news release.
The researchers used a new type of magnetic resonance imaging (MRI) to take brain scans of 16 high school players, ages 15 to 17, before and after a season of football. They found significant changes in the structure of the grey matter in the front and rear of the brain, where impacts are most likely to occur, as well as changes to structures deep inside the brain. All participants wore helmets, and none received head impacts severe enough to constitute a concussion.
The study, which also included researchers from Duke University and the University of North Carolina at Chapel Hill, is published in the November issue of Neurobiology of Disease. It is one of the first to look at how impact sports affect the brains of children at this critical age. Chapel Hill.
While a single knock on the head may not be harmful, mounting evidence shows that repeated blows to the cranium — such as those racked up while playing sports like hockey or football, or through blast injuries in military combat — may lead to long-term cognitive decline and increased risk of neurological disorders, even when the blows do not cause concussion.
Repeated hits to the head
Over the past decade, researchers have found that an alarming number of retired soldiers and college and professional football players show signs of a newly identified disease called chronic traumatic encephalopathy (CTE), which is characterized by a buildup of pathogenic tau protein in the brain. Though still not well understood, CTE is believed to cause mood disorders, cognitive decline and eventually motor impairment as a patient ages. Definitive diagnosis of CTE can only be made by examining the brain for tau protein during an autopsy.
These findings have raised concern over whether repeated hits to the head can cause brain damage in youth or high school players, and whether it is possible to detect these changes at an early age.
“There is a lot of emerging evidence that just playing impact sports actually changes the brain, and you can see these changes at the molecular level in the accumulations of different pathogenic proteins associated with neurodegenerative diseases like Parkinson’s and dementia,” Liu said. “We wanted to know when this actually happens — how early does this occur?”
“Although our study did not look into the consequences of the observed changes, there is emerging evidence suggesting that such changes would be harmful over the long term,” Liu said.
Tests revealed that students’ cognitive function did not change over the course of the season, and it is yet unclear whether these changes in the brain are permanent, the researchers say.
“The brain microstructure of younger players is still rapidly developing, and that may counteract the alterations caused by repetitive head impacts,” said first author Nan-Ji Gong, a postdoctoral researcher in the Department of Electrical Engineering and Computer Sciences at UC Berkeley.
However, the researchers still urge caution – and frequent cognitive and brain monitoring – for youth and high schoolers engaged in impact sports.
“I think it would be reasonable to debate at what age it would be most critical for the brain to endure these sorts of consequences, especially given the popularity of youth football and other sports that cause impact to the brain,” Liu said.