This Sunday, the television event of the year takes place - the 2015 Super Bowl. But as you sit down to enjoy the game, spare a thought for the players; a new study finds that if they started playing football before the age of 12, they may be more likely to have memory and thinking problems as adults.

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Starting football before the age of 12 was associated with poorer memory and thinking in adulthood among NFL players.

In tackle sports such as football, blows to the head are inevitable. It is estimated that emergency departments in the US treat 173,285 sports- and recreation-related traumatic brain injuries (TBIs) - such as concussion - each year among children and adolescents under the age of 19.

But how do such injuries sustained in childhood affect the brain later in life? This is a question that has raised much debate. Some studies have suggested that children may recover better from head injuries than adults because their brain is still developing, but other research has suggested the opposite.

In this latest study, published in the journal Neurology, senior author Robert Stern and colleagues from the Boston University School of Medicine, MA, set out to gain a better understanding of how brain injuries sustained in childhood impact cognitive function in adulthood.

20% poorer test scores for NFL players who began football before the age of 12

To reach their findings, the team analyzed 42 former National Football League (NFL) players aged between 40 and 69 who had been experiencing thinking and memory problems for at least 6 months.

Fast facts about TBI
  • Sports- and recreation-related TBIs among children and adolescents in the US have increased by 60% over the past 10 years
  • The activities associated with the most TBI-related emergency department visits include cycling, football, playground activities, basketball and soccer
  • Males account for more than 70% of sports- and recreation-related TBI emergency department visits.

Learn more about TBI

Around half of the participants began playing football before the age of 12, while the remaining participants started playing after this age. Both groups had sustained a similar number of concussions throughout their career.

The team says they used the age of 12 as a break-off point between the two groups as this is the age at which brain development tends to peak in boys. Stern explains there is a significant rise in blood flow to the brain around this age, which triggers peak volume in brain structures like the hippocampus - important for memory.

All participants were required to complete a number of tests that measured their verbal IQ, memory and executive function.

The team found that the participants who started playing football before the age of 12 performed up to 20% worse on all tests, compared with those who began playing football after the age of 12. These results remained significant even after the researchers accounted for the total number of years the participants had played football.

The team notes that they were particularly interested in the results of a reading test - called the Wide Range Achievement Test, 4th edition (WRAT-4). This test measures a person's ability to pronounce words correctly.

The team hypothesizes that the significantly lower scores on the WRAT-4 test found among participants who began playing football before the age of 12 may indicate that repeated head trauma during childhood limits intelligence in adulthood, though they say further research in this area is required.

Commenting on the findings, Stern says:

"Our study suggests that there may be a critical window of brain development during which repeated head impacts can lead to thinking and memory difficulties later in life. If larger studies confirm this association, there may be a need to consider safety changes in youth sports."

The researchers say that since the study only included NFL players, it may not be generalizable to other populations. Still, they say their findings help shed light on the potential later-life impact childhood brain trauma may have.

In an editorial linked to the study, Dr. Christopher M. Filley, of the University of Colorado School of Medicine, says it is important to gain a better understanding of the implications of contact sports in childhood.

"Football has the highest injury rate among team sports," he notes, "and given that 70% of all football players in the United States are under the age of 14 and that every child aged 9-12 can be exposed to 240 head impacts during a single football season, a better understanding of neurobehavioral sequelae among children who play football is urgently needed."

He points out, however, that since this study did not account for the total number of head impacts each player sustained in their career, it is "possible that the number of impacts is responsible for the reported results rather than the early age of exposure to football."

Medical News Today recently reported on a study revealing that repeated blows to the head among professional fighters may cause brain shrinkage and slow processing.