Players With C.T.E. Doubled Their Risk With Every 5.3 Years in Football

Players With C.T.E. Doubled Their Risk With Every 5.3 Years in Football

October 7, 2019

Former tackle football players with chronic traumatic encephalopathy, the degenerative brain disease linked to repeated head hits, doubled their risk of developing the worst forms of the disease for each 5.3 years they played, according to a new study.

Scientists have known that more years playing tackle football is associated with thinking and memory deficits later in life. This study builds on that research and, for the first time, calculated the number of years played with levels of measurable disease in the brain.

The retrospective analysis in the new study was based largely on brains found to have C.T.E. that were donated to researchers at Boston University, not the far larger universe of football players who did not donate their brains to science. Brain scientists do not know what the underlying, baseline risk is for all players.

The findings, based on the lives of 266 former amateur and professional players whose brains were donated to the C.T.E. Center at Boston University, were published in the medical journal Annals of Neurology. Of those players, 43, or about 16 percent, were found not to have C.T.E.

According to the study, the risk of developing C.T.E. rose by 30 percent each year played when surveying all the players, including those who did not develop the disease.

The study was funded by the National Institutes of Health, the Department of Defense, the Department of Veterans Affairs, the Alzheimer’s Association, the National Operating Committee on Standards for Athletic Equipment, the Nick and Lynn Buoniconti Foundation, the Concussion Legacy Foundation, the Andlinger Foundation, WWE and the National Football League.

Family members provided information about how long the brain donors played football and other sports.

For brain donors who played fewer than 4.5 years, the chance that they would develop C.T.E. was about one-tenth of what it was for those who played longer, the study found. Those athletes who played more than 14.5 years were 10 times more likely to develop C.T.E. than those who played fewer years, though several players with careers 15 years or longer were not found to have C.T.E.

C. T. E., which can only be diagnosed after death, is identified by the buildup of a tau protein in certain portions of the brains. It has been associated with mood swings, depression, dementia, impulse control issues and suicidal thoughts.

Because there is currently no test that can diagnose the disease in the living, researchers have tried to reconstruct the lives of deceased players to establish their exposure to tackle football and other activities that may have contributed to its development.

Researchers at Boston University have previously said that players who started playing tackle football before the age of 12 had more behavioral and cognitive problems later in life than those who started playing after they turned 12.

Other researchers have questioned studies that have shown a high percentage of deceased former football players found with C.T.E. They claimed that the research subjects were self-selected because the families of players who thought that they had brain disease were more likely to donate their brains to science.

There are only about 20,000 retired N.F.L. players and tens of thousands of former collegiate players. The Boston group’s work has been based on a sample of some of the worst cases. Many, perhaps most, football players do not develop disabling cognitive problems, and there are likely many other brain traumas that could potentially result in the prevalence of the tau protein that is associated with C.T.E.

Some researchers are looking at broader populations of people who have had traumatic brain injury, not just football players, to determine whether participation in collision sports, as opposed to genetics or other factors, is linked to the development of C.T.E.

Still, studies linking repeated head hits and brain disease have spurred a public debate about the safety of youth and high school football. While some researchers are calling for children to avoid collision sports, others question whether there is a direct link between exposure to repeated hits to the head absorbed in games like tackle football and the development of cognitive and neurological problems later in life.

To help settle the debate, scientists are trying develop a test that can identify abnormal tau protein accumulation associated with C.T.E. in living patients. As with Alzheimer’s and other diseases that affect the brain, researchers have spent years trying to refine the tests. They remain years away from developing a clinical test to determine the presence of C.T.E. in living players.

Benedict Carey contributed reporting

Ken Belson covers the N.F.L. He joined the Sports section in 2009 after stints in Metro and Business. From 2001 to 2004, he wrote about Japan in the Tokyo bureau.

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