Evidence of CTE -- a degenerative brain disease that can be diagnosed only at autopsy -- was found in 19.2% of donors who played hockey for less than 13 years, 51.9% of those who played for 13 to 23 years, and 95.8% of those who played for more than 23 years, reported Jesse Mez, MD, MS, of Boston University, and co-authors.

The Boston University CTE Center study of 77 dead male ice hockey players showed that the risk for the brain disease jumped by 34% with each year played.

Eighteen of the 19 NHL players whose brains were studied after death were discovered to have chronic traumatic encephalopathy.