Many U.S. football players had brain disease, data show | Science News for Students

Many U.S. football players had brain disease, data show

Severe disease showed up in 99 percent of pro players whose brains had been donated to science
Aug 16, 2017 — 7:00 am EST
American football tackle

Football collisions can lead to head injuries. New data from brains donated to science show that from high school players to former pros, many men sustained serious permanent damage. And how much damage occurred was not always obvious, based on symptoms reported by the men’s families.


American football is a very rough and tumble sport. A career of hard knocks and smashups can take a brutal toll on players’ bodies. That includes their brains, a new study shows. Most football players whose brains were donated at death for research showed severe damage, according to the largest study to date.

The finding provides more evidence linking serious brain disease with repetitive head injuries sustained during years of playing American football.

The authors caution, however, that they don’t know how representative the brains were that they studied. Players and their families had offered up these brains for study. Their choosing to do so may reflect that many of these players already had major symptoms of brain damage. So these may have been a self-selected group of the most injured of players, not a representative mix of all players. Still, the study’s authors find their new results worrisome.

They examined the brains of 202 former football players. Of them, 177 had CTE, short for chronic traumatic encephalopathy (En-sef-uh-LOP-ah-thee). The term means a brain has sustained long-term damage. CTE’s symptoms can include mood and behavioral issues as well as problems with thinking and reasoning.

Men who had played in the National Football League donated 111 of the brains studied. And 110 of these — a whopping 99 percent — had CTE. So did three of 14 high school players and 48 of 53 college players.

Twenty-seven researchers from eight universities, hospitals and research groups took part. The team based its diagnoses on brain autopsies. It also interviewed family and friends about any symptoms the players had experienced. The researchers described their disturbing findings July 25 in JAMA.

“The fact that [CTE] was so common adds to our concern about the safety of playing football,” says Gil Rabinovici. As a neurologist, he studies nerve tissues and the brain at the University of California, San Francisco. He also offered an editorial accompanying the new report. The strong link between brain damage and football injuries, he says, “hovers like a dark cloud over the game at all levels.” And that’s true “even if the study cannot address how frequent the disease is, or who is at risk.”

Growing concerns over football’s risk of CTE

CTE can show up in athletes and others who’ve had repetitive head injuries, such as concussions. The only way to diagnose CTE is with an autopsy. In affected brains, a protein called tau goes “bad.” It inappropriately forms clumps in nerves and other brain cells. A tau buildup occurs in other brain diseases, too — such as Alzheimer’s. But where it builds up is different in CTE. Here, the protein congregates in cells around small blood vessels.

Clumps of the protein tau (dark red) show up more widely throughout the brain as 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.

In 2008, researchers set up a brain bank to collect tissues for study. Its goal was to probe the long-term effect of head blows sustained in sports and military service. The new study focused on brains from football players provided to that tissue bank.

Neurologist Jesse Mez of Boston University School of Medicine, in Massachusetts, and his colleagues classified CTE cases as mild or severe. Their ratings were based on how widespread the tau clumps were within a brain. The severity of disease seemed to track with how long the men had spent playing football, Mez says. Among NFL players, 95 of the 110 diagnosed cases were severe. In contrast, all three high school players’ cases were mild. Among cases in college players’, just over half were judged severe.

The symptoms reported by family members were not a good gauge of how bad a man’s brain damage had been. Behavioral and mood problems — such as impulsivity, anxiety and depression —commonly showed up in both severe and mild cases of CTE. Cognitive symptoms, including memory loss, also were about the same in both groups. One big difference: dementia. It was more common in men with severe CTE than in those who had mild cases.

Why symptoms so poorly correlated with the severity of brain disease is puzzling, Mez says. “The question is: Is there something else going on?” such as inflammation.

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. He works at Washington University School of Medicine in St. Louis, Mo.

Yet detecting CTE in living patients will be crucial for understanding how common it is in the NFL, “let alone in the millions of people who participated in college, high school and youth football,” says Rabinovici. For now, he says, “We need to focus on prevention of concussions and other head impacts at all levels of contact sports.”

Power Words

(more about Power Words)

anxiety     A nervous reaction to events causing excessive uneasiness and apprehension. People with anxiety may even develop panic attacks.

autopsy     Examination of body tissues after a person dies, typically performed to determine the cause of death.

chronic     A condition, such as an illness (or its symptoms, including pain), that lasts for a long time.

chronic traumatic encephalopathy (or CTE)    The term for long-lasting brain disease brought on by head injuries (often sustained in sports or military service). This disease tends to be progressive, meaning it worsens with time.

cognitive     A term that relates to mental activities, such as thinking, learning, remembering and solving puzzles.

colleague     Someone who works with another; a co-worker or team member.

concussion     Temporary unconsciousness, or headache, dizziness or forgetfulness due to a severe blow to the head.

deceased     An adjective that describes someone who has died.

dementia     A type of mental disorder caused by disease or injury that causes people to gradually lose all or part of their memory. It may start out temporary and build to a permanent condition where the ability to reason also is impaired.

depression     A low spot, such as in a field or the surface of a rock. (in medicine) A mental illness characterized by persistent sadness and apathy. Although these feelings can be triggered by events, such as the death of a loved one or the move to a new city, that isn’t typically considered an “illness” — unless the symptoms are prolonged and harm an individual’s ability to perform normal daily tasks (such as working, sleeping or interacting with others).

diagnose     To analyze clues or symptoms in the search for their cause. The conclusion usually results in a diagnosis — identification of the causal problem or disease.

encephalopathy     A term for any type of disease that alters the structure of the brain or how well it functions.

gauge     A device to measure the size or volume of something. For instance, tide gauges track the ever-changing height of coastal water levels throughout the day. Or any system or event that can be used to estimate the size or magnitude of something else. (v. to gauge) The act of measuring or estimating the size of something.

impulsivity    To react to some event or suggestion without regard to the potential long-term consequences of this decision.

inflammation     The body’s response to cellular injury and obesity; it often involves swelling, redness, heat and pain. It also is an underlying feature responsible for the development and aggravation of many diseases, especially heart disease and diabetes.

link     A connection between two people or things.

nerve     A long, delicate fiber that transmits signals across the body of an animal. An animal’s backbone contains many nerves, some of which control the movement of its legs or fins, and some of which convey sensations such as hot, cold or pain.

neurology     A research field that studies the anatomy and function of the brain and nerves. People who work in this field are known as neurologists (if they are medical doctors) or neuroscientists if they are researchers with a PhD.

protein     A compound made from one or more long chains of amino acids. Proteins are an essential part of all living organisms. They form the basis of living cells, muscle and tissues; they also do the work inside of cells. Among the better-known, stand-alone proteins are the hemoglobin (in blood) and the antibodies (also in blood) that attempt to fight infections. Medicines frequently work by latching onto proteins.

risk     The chance or mathematical likelihood that some bad thing might happen. For instance, exposure to radiation poses a risk of cancer. Or the hazard — or peril — itself. (For instance: Among cancer risks that the people faced were radiation and drinking water tainted with arsenic.)

symptom     A physical or mental indicator generally regarded to be characteristic of a disease. Sometimes a single symptom — especially a general one, such as fever or pain — can be a sign of any of many different types of injury or disease.

tissue     Made of cells, any of the distinct types of materials that make up animals, plants or fungi. Cells within a tissue work as a unit to perform a particular function in living organisms. Different organs of the human body, for instance, often are made from many different types of tissues.

trauma    (adj. traumatic) Serious injury or damage to an individual’s body or mind.


Journal:​ J. Mez et al. Clinicopathological evaluation of chronic traumatic encephalopathy in players of American football. JAMA. Vol 318, July 25, 2017, p. 360. doi:10.1001/jama.2017.8334.

Journal:​ G. Rabinovici. Advances and gaps in understanding chronic traumatic encephalopathy. JAMA. Vol 318, July 25, 2017, p. 338.  doi:10.1001/jama.2017.9353.