Cumulative Brain Damage in Athletes Can Occur Without Concussion


June 25, 2020

Even athletes who don’t experience concussion but suffer repeated jolts or falls inherent in contact sports can experience subtle and cumulative brain changes, new imaging research suggests.

A group of female college rugby players who had not experienced a concussion for at least 6 months prior to or during the study and who showed no outward symptoms of brain injury or brain changes up to 2 years later were found to have undergone changes in brain structure and connectivity.

Interestingly, no such changes were observed in the brains of female athletes who participated in the noncontact sports of rowing and swimming.

Although the rugby players’ brains showed some signs of recovery during off-seasons, there was a cumulative effect of brain changes over the following years.

Senior investigator Ravi S. Menon, PhD, professor of medical biophysics at Western University in London, Ontario, Canada, said the study shows how head injuries fall on a spectrum, with concussions on one end of the spectrum and subclinical injury on the other.

“But repeated lower-impact hits can…cause similar kinds of damage that we see in concussed individuals, and the more seasons you play, the more damage you accumulate,” Menon told Medscape Medical News.

The findings were published online June 17 in Neurology.


The study included 70 rugby players from Western University who played on the team during at least part of a 5-year period. Most participated in the study for 1 year, and 12 were followed for 2 years or longer. Also included were 31 female college swimmers and rowers from the same university’s teams.

Menon said the investigators included noncontact athletes to assess whether any brain changes might occur that were unrelated to brain impacts but were instead related to intense exercise or team competition.

The researchers also analyzed a subset of 37 rugby players and nine rowers who wore impact accelerometer sensor headbands during practice and competition to record the impact of indirect jolts to the brain.

The Sport Concussion Assessment Tool (SCAT3) was used to assess clinical symptoms and cognitive and memory performance.

The study’s primary outcome measures were diffusion and resting-state functional MRI (rs-fMRI).

Twenty-six rugby players experienced an average of three significant impacts during two practices or a preseason game, but these impacts did not cause concussion. None of the nine rowers experienced any significant head impacts.

Results showed a number of differences in the structure and connectivity in the rugby players’ brains in comparison with those of swimmers and rowers.

Information Highways

The investigators found changes in white matter diffusion measures and rs-fMRI network connectivity in concussion-free contact sport athletes compared to noncontact athletes.

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