Scientists looking for a link between repeated brain trauma and lasting neurological damage typically study the brains of soldiers or football players. But it’s unclear whether this damage—known as chronic traumatic encephalopathy (CTE)—is prevalent in the general population. Now, a new study reports those rates for the first time. Researchers sorted through nearly 3000 brains donated to the Mayo Clinic’s tissue registry between 2005 and 2016. Then, by scanning obituaries and old yearbooks, the researchers narrowed the group to 300 athletes who played contact sports and 450 nonathletes. Finally, they collected medical records and looked under a microscope at tissue from up to three sections of each brain for signs of CTE.
6% of the brains showed some or all signs of CTE, researchers report in Brain Pathology. Not all the people experienced symptoms associated with CTE, at least according to their medical records. People who played contact sports were more likely to have signs of CTE. 9% of athletes had evidence of CTE, compared with just over 3% of nonathletes.