Even without concussions, just one football season may damage players’ brains

A season of head hits left its mark on college football players’ brains, even when those hits didn’t cause concussions. Routine head bumps over the course of a season were linked to abnormal brain tissue in part of players’ brain stems, researchers report August 7 in Science Advances.

It’s unclear if these brain stem changes affect mental performance, or whether the changes are permanent. But the study suggests that in addition to the big hits that cause concussions, these smaller knocks could cause trouble.

During the 2011, 2012 and 2013 football seasons, a team led by researchers at the University of Rochester in New York recruited players from the university to participate in a study looking at head impacts and brain health. Each player wore an accelerometer in his helmet to capture the forces at play during all practices and games during a single season. The players also underwent pre- and post-season brain scans. A measure called fractional anisotropy let researchers estimate how well stretches of white matter brain tissue can carry neural signals, a key job of healthy brain tissue.

The 38 players included in the study collectively took 19,128 hits. And by the end of their season, the players on average had lower measures of fractional anisotropy in their right midbrains — a part of the brain stem. These declines were more tightly linked to the number of hits that twisted heads, as opposed to direct head-on hits. Those rotational forces might be particularly damaging to brain tissue, a finding that fits with results from earlier studies, the researchers write.