A majority of football players whose brains were donated for research suffered a degenerative brain disease during their lives, according to the largest sample of players ever studied. The finding provides more evidence that the repetitive injuries to the brain sustained while playing American football are associated with the disease, researchers say.
Of 202 deceased former football players, 177 were diagnosed with chronic traumatic encephalopathy, which can cause a host of mood and behavioral issues as well as thinking and reasoning problems. Among 111 men who had played in the National Football League, 110 — a whopping 99 percent — had developed the disease, researchers report July 25 in JAMA. Three of 14 high school players also showed signs of the brain disease, as well as 48 of 53 college players. Researchers relied on brain autopsies of the players to make the diagnoses and interviewed family members and friends about the symptoms players had experienced.
This doesn’t necessarily mean all football players experience chronic traumatic encephalopathy. Many of the families who donated the brains for research could have been motivated to do so because their loved ones had noticeable symptoms, so the sample is not necessarily representative of the general football population. The results are still worrisome, though, researchers say.
Red and redder
Clumps of a protein called tau (dark red) become more widely distributed in the brain as chronic traumatic encephalopathy (CTE) progresses from mild (top), as seen here in the brain from a former college football player, to severe (bottom), as seen in a brain of an NFL player.
“The fact that chronic traumatic encephalopathy was so common adds to our concern about the safety of playing football and the risk of developing neurologic symptoms later in life,” says neurologist Gil Rabinovici of the University of California, San Francisco, who wrote an editorial accompanying the article. This “hovers like a dark cloud over the game at all levels, even if the study cannot address how frequent the disease is, or who is at risk.”
Chronic traumatic encephalopathy, or CTE, shows up in athletes and others who’ve had repetitive injuries to the head, such as concussions. The only way to diagnose the disease is with an autopsy. In brains with the condition, a protein called tau goes “bad” and forms clumps in nerve cells and other brain cells. Although tau buildup is found in other brain diseases, like Alzheimer’s, in CTE, the protein congregates in brain cells around small blood vessels.
In 2008, a research team set up a brain bank to study the impact of head blows resulting from contact sports or military service. Behavioral neurologist Jesse Mez of Boston University School of Medicine and his colleagues classified players as having mild or severe CTE, depending on how widespread the tau clumps were in the players’ brains. The severity of disease seemed to track with the number of years spent playing football, says Mez. Among NFL players, 95 of the 110 diagnosed cases were severe. All three of the high school players’ cases were mild, while just over half of the college players’ cases were severe.
Yet the players’ reported symptoms while alive were similar, regardless of the severity seen in the brain. Behavioral and mood problems, such as impulsivity, anxiety and depression, were commonly reported in both severe and mild cases of the disease. Cognitive symptoms, including memory loss, were also typical for both groups. One major difference, Mez notes, was that dementia was more common in severe cases of CTE than in mild cases.
As for why players reportedly experienced similar symptoms no matter the severity, “the question is, is there something else going on,” such as inflammation, Mez says. “Or are there regions of the brain that we’re not looking carefully enough at?”
There still isn’t a way to diagnose CTE during life, and that’s “the 800-pound gorilla in the room,” says neurologist David Brody of Washington University School of Medicine in St. Louis.
Detecting the disease in patients will be crucial for understanding how common CTE is in the NFL, “let alone in the millions of people who participated in college, high school and youth football,” says Rabinovici. “In the meantime, we need to focus on prevention of concussions and other head impacts at all levels of contact sports.”