Force of hits, not just number, raises CTE risk

The clearest predictor of what could cause a person to suffer the brain disease CTE later in life is the cumulative force of thousands of hits to the head, and not just the sheer volume of concussions, research shows.

For years, researchers studying chronic traumatic encephalopathy, or CTE, believed the primary cause of it was repetitive hits to the head, whether or not those hits caused concussions. They believed the more frequently that a person sustained head blows, the more likely they were to develop neurological and cognitive struggles later in life.

The new study in Nature Communications adds a wrinkle to the research.

The study is the largest one to date, examining root causes of CTE, which is associated with everything from memory loss to impulsive behavior to suicidal thoughts and depression.

Using data from 34 published studies that tracked blows to the head measured by sensors inside of football helmets, the researchers were able to see how 631 former football players, whose brains were donated for research to Boston University, have been affected.

The study found that 71% of the brains examined—451 of the 631—had some level of CTE, while 180 showed no sign of the disease. The worst forms of CTE showed up in players who had absorbed the greatest cumulative force of hits to the head, meaning they were hit often and hard. (The individuals who absorb the hardest hits to the head are defensive backs, wide receivers, and running backs.)

Senior author Jesse Mez is an associate professor of neurology at the Chobanian & Avedisian School of Medicine, as well as the associate director of the Boston University’s Alzheimer’s Disease Research Center and codirector of clinical research at the BU CTE Center. Here he clarifies the study findings and where CTE research goes next: