What Effect do Sub-concussive Impacts have on the Brain?

Without sustaining a single concussion, a North Carolina high school American football team showed worrisome brain changes after a single season, a new study has shown.

A detailed effort to capture the on-field experiences of 24 high school football players showed that, at the end of a single season of play, teammates whose heads sustained the most frequent contact with other moving bodies had the most pronounced changes in several measures of brain health.

In the study, researchers focused on 24 members of a single high school football squad, wiring up each player's helmet with six accelerometers. During practices as well as play, the sensors gathered data on the location, strength of impact and direction of any blows to a player's head.

The study's 24 subjects were 17 years old on average. None had ever had a diagnosed concussion, and no concussions were seen in the course of the team's season.

Before the season began as well as after it ended, the North Carolina players underwent brain-imaging scans that measured the density of key brain structures and analysed certain patterns of electrical activity generated by their working brain cells.

The scans showed that the condition of the brain's white matter was most affected in players whose helmets had recorded the most linear acceleration - the kind of direct frontal hit a receiver might get when returning a kick, or that a lineman might sustain repeatedly when lunging forward on every play.  Whilst a quarterback or ball-runner who is tackled laterally was most likely to withstand strong rotational forces.

It was noted that different kinds of brain changes are linked to "very different" kinds of impacts.

As researchers begin to recognise whether long-term behavioral effects - say, depression, memory loss or movement disturbances - come with certain brain changes, they can begin to protect players accordingly.

Mounting evidence already suggests that sustaining multiple concussions puts a person at higher risk of later depression, memory loss and other neuropsychiatric problems, but researchers now suspect that even when they don't result in a concussion diagnosis, repeated blows to the head may be harmful as well.

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