Most U.S. Pro Football Players Suffer Severe Neurodegenerative Disease, NFL Study Reveals

National Football League athletes might be at increased risk of chronic traumatic encephalopathy (CTE), a brain condition linked to dementia and abnormal behavior.

A recent study published in JAMA found that 87 percent of investigated players had signs of brain damage after death. Dementia was diagnosed in 85 percent of those with severe CTE, 32 percent of whom also had a diagnosis of Alzheimer’s disease.

But although the study, “Clinicopathological Evaluation of Chronic Traumatic Encephalopathy in Players of American Football,” provides a strong case linking brain damage and disease with football, researchers cautioned that the players investigated might not be representative of U.S. football players in general.

The participants had all voluntarily donated their brains to research, and since all those diagnosed with CTE after death had shown symptoms while alive, the Boston University School of Medicine research team figured that disease awareness might have spurred their participation in the research.

The brain bank included people who had been exposed to head trauma, and playing American football was sufficient to be included. The team examined the brains of 202 deceased football players, and found signs of CTE in 177 of them.

CTE is a condition characterized by cognitive difficulties and behavioral abnormalities such as depression or aggressive behavior.

Researchers found brain changes all but one of the 111 NFL athletes examined. Only those who had played in high school had mild disease. The remaining players, including those who played in college, had severe CTE — and of those with severe CTE, most had died of causes related to neurodegeneration.

In addition, all those with CTE had neurofibrillary tangles made up of the Alzheimer’s-associated protein tau, and a large proportion also had amyloid-beta deposits. Among those in the most severe disease stage, 91 percent had amyloid aggregates.

Researchers also found other proteins, such as the Parkinson’s disease-related alpha synuclein and TDP-43, which is linked to amyotrophic lateral sclerosis (ALS). In addition, they collected information about the players through interviews with family members or close friends. It turned out that none of the players who had CTE brain changes was free of symptoms while alive.

Cognitive issues appeared as the first symptoms in 42.3 percent of those players examined, with about the same proportion showing behavioral abnormalities as the first symptom. A small group had developed both behavioral and cognitive issues at the same time.

Impulsivity, depression, apathy and anxiety were common. Many patients also felt hopelessness or explosivity, or were verbally or physically violent. Suicide was the most common cause of death among those with mild CTE, and suicidal behavior was common also in those who did not commit suicide.

Cognitive problems were reported in 95 percent of players with severe disease, and 25 percent had been diagnosed with Alzheimer’s while alive. Many severe cases also had motor problems while alive.

While the study presents and convincing link between American football and CTE, researchers cautioned that the players might not be representative, and so, the disease rates might be overestimated.