The prevalence of chronic traumatic encephalopathy (CTE) in American football players is shockingly high according to a paper published online in JAMA (Journal of the American Medical Association) on July 25th (1).
The paper describes autopsy results from a convenience sample of 202 deceased football players who donated their brains for research. CTE was diagnosed in 87% of cases.
CTE was found in all but one of 111 (99%) participants who were former National Football League (NFL) players.
The most common cause of death for participants with mild CTE pathology was suicide (12 cases; 27%) and for those with severe pathology was neurogenerative disease (i.e., dementia related and Parkinson related) (62 cases; 47%).
The study provides the largest CTE case series described so far. All the participants were exposed to a relatively similar type of repetitive head trauma while playing the same sport.
However, as the authors of the paper point out, a major limitation is ascertainment bias associated with participation in the brain donation program. In other words, awareness of a possible link between repetitive head trauma and CTE may have motivated players and their families with symptoms and signs of brain injury to participate in this research. Hence those without symptoms may be less likely to participate. Therefore, estimates of the real prevalence of CTE are not provided by this study.
In a recent interview, Daniel H. Deneshvar, one of the authors of the paper said (2):
Although at this point we cannot make any firm sweeping health statements about what types of hits cause CTE or about other risk factors, such as genetic risk, we can say that the fact that so many athletes develop CTE is very concerning, considering that we have children as young as 8 years old playing football and potentially subjecting themselves to this disease.
What is Chronic Traumatic Encephalopathy (CTE)?
CTE is a neurodegenerative disorder believed to be associated with exposure to repetitive head trauma. It is characterized by fibrillated tangles of hyerphosopholarated tau (p- tau) within the brain.
In humans, tau proteins are mostly found within the central nervous system where they may have an important stabilizing role. Both Alzheimer’s disease and Parkinson’s disease are associated with tau proteins that have become defective.
The term tauopathy is sometimes used to describe diseases caused by misfolding of the tau protein (3).
Although repeated physical trauma seems to be a prerequisite for the development of CTE, many athletes, including boxers and American football players, never develop the disease. So obviously, other factors are involved as well, some may be environmental and some may be genetic (4). In theory, a certain genetic predisposition might make some individuals who suffer repeated head trauma more vulnerable than others.
The Symptoms of CTE
CTE is believed to have two distinct initial clinical presentations: one with behavior or mood changes, typically at a relatively young age, and the other with cognitive symptoms. Several clinical subtypes have been suggested (5).
The symptoms are divided into three categories.
- Neuropsychiatric: Increased impulsivity, explosivity, violence, rage, depression, apathy, substance abuse, and suicidal behavior.
- Cognitive: Impaired attention, executive function, and memory.
- Motor: Parkinsonism, difficulty swallowing (dysphagia), slurred speech (dysarthria), and poor coordination.
The early symptoms often include memory problems, irritability, depression, emotional lability, suicidal behavior, and substance abuse. Later, worsening of aggression, motor impairments, and dementia may occur.
The History of Chronic Traumatic Encephalopathy (CTE)
In the film Concussion from 2015, Will Smith portrays Bennet Omalu, a Nigerian born neuropathologist. Omalu discovered signs of CTE in Mike Webster, the Hall of Fame center for the Pittsburgh Steelers who died in 2002. This finding sparked a chain of events that ultimately forced the NFL to settle a class-action lawsuit from retired players and raised unprecedented awareness of the dangers of football head trauma (6).
However, the history of CTE can be traced all the way back to 1928 when Harrison Martland described a “peculiar condition” described as “punch drunk” in boxers (7).
For some time fight fans and promoters have recognized a peculiar condition occurring among prize fighters which, in ring parlance, they speak of as “punch drunk.” Fighters in whom the early symptoms are well recognized are said by the fans to be “cuckoo,” “goofy,” “cutting paper dolls,” or “slug nutty.”
The phenomenon came to be known as ‘dementia pugilistica’ by Millspaugh in 1937 (8), and then the term ‘psychopathic deterioration of pugilists’ was introduced by Courville (9) The word pugil comes from Latin, meaning boxer.
In 1934, Parker described three three professional boxers with signs of neurological disease after their boxing careers were over which he referred to as “traumatic encephalopathy” (10).
In 1957, Macdonald Critchley wrote an article in the British Medical Journal describing the medical aspects of boxing from a neurological standpoint (11). Critchley wrote:
There is much in boxing to interest a practicing neurologist, and special attention should be focused upon (1) the phenomenon of groggy states as occurring during or after a contest, and (2) the condition known as traumatic progressive encephalopathy (or punch-drunkenness).
In 1969, Anthony Herber Roberts wrote a book called Brain damage in boxers: Study of the prevalence of traumatic encephalopathy among ex-professional boxers. He found that among 221 retired boxers studied, 11% had mild CTE, and 6% had moderate to severe CTE.
In 1994, Roberts and coworkers found deposits of beta amyloid protein deposits similar to Alzheimer’s disease in patients who had suffered a severe injury to the head (12). Subsequently, several investigators reported pathologic findings in the brain associated with chronic traumatic head injury, particularly among boxers (13).
In 2005 and 2006 Omalu published two papers describing CTE in two retired NFL players (14, 15). In 2010, he published his third case report article addressing a retired NFL player who had committed suicide by a gunshot to the head (16). Omalu concluded that his case series manifested similar clinical history of neuropsychiatric impairment with autopsy evidence of cerebral tauopathy.
Although almost 90 years have passed since Millspaugh coned the term dementia pugilistica, research into CTE still seems to be in its infancy.
The diagnosis of CTE is most often based on autopsy findings, and there is no definitive diagnostic test for the disease in living people. However, CTE should be considered in the presence of a neurological and psychiatric decline in a previously healthy individual, in particular, if there is a history of head trauma.
Initially, CTE appeared to be primarily associated with boxing. The famous boxer Mohamed Ali was diagnosed with Parkinson’s disease in 1984. It has been widely argued, but never proven, that the multiple head injuries Muhammad Ali sustained during his boxing career could have caused his Parkinson’s disease.
Recently, American football has been associated with an increased risk of CTE. The list of former NFL players with signs of CTE at autopsy is shocking (see below) (17):
It seems pretty difficult nowadays to deny a link between CTE and repeated traumatic brain injury associated with sports like boxing, American football, and mixed martial arts like the Ultimate Fighting Championship (UFC).
What is frightening is that these sports are immensely popular and the amount of money involved is colossal. So, the risk of denial is palpable.
Never forget that CTE is a dreadful disease that commonly results in death. Furthermore, it causes grave suffering to family and friends of the victim.
Currently, there is no treatment available for CTE. Prevention is the only cure.