Signs of degenerative brain disease are widespread among a sample of donated brains of former football players, researchers reported Tuesday in Journal of the American Medical Association.
The finding supports a link between playing American football and developing Chronic traumatic encephalopathy (CTE), which is linked to repeated blows to the head and was first described in boxers. However, large studies provide little new information about the disease, its progression, or evolution.
The brain bank of 202 former football players was a “convenience sample,” meaning it was a biased sample and not representative of football players as a whole. Instead, players and their families donate brains after players have experienced symptoms linked to CTE during life or players are suspected or considered at risk of developing CTE. The athletes in the sample reported higher rates of lifetime CTE symptoms than those found in studies of lifetime, retired National Football League (NFL) players. Furthermore, the study only had pathology data from one time point—after death—so the progression of the disease could not be assessed. And, finally, the study did not include brain sampling from people who were not exposed to a control group.
Overall, the study doesn’t tell us much about the possible prevalence of CTE among football players, a person’s absolute risk of developing the disease, or the higher relative risk that football players may have compared with non-players. play football
However, it adds to the growing body of evidence linking hard hits in American football and other high-impact sports to the development of CTE. The devastating disease is associated with progressive memory problems, dementia, depression, and anger.
CTE is diagnosed through a post-mortem examination of the brain. Researchers look for abnormal protein clusters that accumulate near small blood vessels. Mild cases of CTE show these defects at the outer level of the brain, while those with severe cases have them in deeper areas of the brain.
For the study, the researchers (led by Boston University neuropathologist Ann McKee) relied on a bank of brains from players considered at risk of CTE. The players have experienced repetitive head damage during life through football. Their median death rate was 66. In a sample of 202 brains, 177 (87 percent) had signs of CTE.
Breakdown: 110 of 111 (99 percent) NFL players diagnosed with CTE; seven of eight (88 percent) Canadian Football League players; 48 of 53 (91 percent) college football players; 9 of 14 (64 percent) semi-professional players; 3 of 14 (21 percent) high school players; and 0 of two prior high school players. The three high school players with CTE all had minor cases. But the remaining player categories had a mix of mild and severe.
From extensive online and phone surveys of players’ family members, researchers collected clinical data about possible CTE symptoms and their progress of 111 players with CTE. Psychiatric pathology data linked with clinical data. For example, among the 84 participants with severe CTE symptoms in their brain, 75 (89 percent) had behavioral or mood symptoms or both, 80 (95 percent) had cognitive symptoms, and 71 (85 percent ) have signs of dementia, the researchers reported. . The finding offers a correlation that supports similar findings in previous work, but does not prove that brain abnormalities cause the symptoms.
Previous studies found that about six percent of retired NFL players over age 56 reported memory problems and about 11 percent experienced depression.
In a statement, the NFL responded to the investigation saying:
We appreciate the work of Dr. McKee and his colleagues for their contribution to ongoing research for a better understanding of CTE. Case studies such as those compiled in this update are important to further advance knowledge and progress related to head injury. The medical and scientific communities will benefit from this publication, and the NFL will continue to work with many experts to improve the health of current and former NFL athletes. As noted by the authors, there are still many unanswered questions related to the cause, incidence, and evolution of the long-term effects of head trauma such as CTE. The NFL is committed to supporting scientific research into CTE and improving progress in the prevention and treatment of head injuries.
JAMA2017. DOI: 10.1001 / Jama.2017.8334 (About DOIs).