Routine hits in a single football season may harm players’ brains

Collisions in practices and games may damage healthy brain tissue, even without concussions


Over a season of college football, head hits that were too small to cause concussions were still linked to adverse changes in the brain stems of players.


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A season of head hits left its mark on the brains of college football players. Those hits didn’t even need to cause concussions, a new study finds. Just routine head bumps throughout the football season were enough to show up as a “signature” of abnormal changes in the players’ brain stems.

Adnan Hirad at the University of Rochester in New York led the new study. It looked for signs of brain changes due to head impacts. Hirad’s team recruited college players to participate in the study during the 2011, 2012 and 2013 football seasons. Each player wore an accelerometer in his helmet. That device captured the intensity and direction of hits at all practices and games during a single season. The players also underwent pre- and post-season brain scans.

A key job of healthy brain tissue is to relay signals from one neuron (nerve cell) to the next. To measure this how well that signaling was, the researchers focused on something called fractional anisotropy (An-eye-so-TROH-pee). It allowed researchers to estimate how well parts of the brain’s white matter carried those neural messages.

Thirty-eight players took part in the study. Together they sustained 19,128 hits to the head. By the end of one season of play, the players’ fractional anisotropy scores had dropped, on average, in their right midbrains. This is a part of the brain stem.

How big the drop was tended to be linked more tightly to the number of hits that rotated a player’s head rather than to the number of direct head-on hits. Those rotational forces might be especially damaging to brain tissue.

Hirad’s team shared its findings August 7 in Science Advances

It’s unclear if the brain-stem changes affect mental performance. Similarly, it’s unknown if the changes will be permanent. But the study suggests that even smaller knocks to the head can cause trouble.

Laura Sanders is the neuroscience writer at Science News. She holds a Ph.D. in molecular biology from the University of Southern California.

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