Multiple hits to the head that occur in contact sports like football and ice hockey can bring on conditions like chronic traumatic encephalopathy (CTE), a neurodegenerative brain disease that often leads to cognitive changes and dementia over time.

Even relatively minor, but repeated head impacts, are associated with concerning brain changes.

The findings of a new study led by researchers at the University of Florida and Boston University suggest that inflammation from repetitive head impacts causes structural changes in the brain, which in turn are associated with symptoms of CTE such as poorer memory. The study only shows an association, the researchers point out, however, not direct cause and effect.

Damage to the white matter in the brain occurred in the limbic system, the part of the brain that regulates emotions, memory, motivation and other behaviors.

The study analyzed data from 223 men, average age 57, including 170 who played college or professional football and compared it to brain data from a control group of 53 men with an average age of 59 who had never played contact sports, served in the military or sustained a concussion.

All participants were enrolled in the Diagnostics, Imaging and Genetics Network for the Objective Study and Evaluation of CTE (DIAGNOSE CTE) Research Project.

Three biomarkers of inflammation were measured in participants' blood and cerebral spinal fluid — interleukin-6, tumor necrosis factor alpha and glial fibrillary acidic protein. Participants also had brain scans so the researchers could examine their brain microstructure and measure the direction that water moved in the brain — known as fractional anisotropy — and its mean diffusivity, how freely water moved through the brain.

Inflammation was more strongly associated with damage to the brain microstructure in former football players than controls. Former football players had lower fractional anisotropy and higher mean diffusivity.

Damage to the white matter in the brain occurred in the limbic system, the part of the brain that regulates emotions, memory, motivation and other behaviors. In former football players, damage to the limbic system was associated with worse memory. No association was seen, however, between inflammation and cognition.

The study included a control group of 53 men who had never played contact sports, served in the military or sustained a concussion.

The association between inflammation and damage to the limbic system were stronger in a subgroup of 57 former football players who were thought likely to have CTE because of their symptoms and histories of repetitive head impacts.

“Because the limbic system influences both cognition and behavior, targeting inflammation could be a way to reduce the risk of brain changes that make symptoms associated with repetitive head impacts worse,” Breton Asken, a senior author on the study and professor of clinical and health psychology at the University of Florida, said in a statement, adding that the team hopes to explore this idea in future research.

The study and a related editorial are published in Neurology.