Chronic traumatic encephalopathy (CTE) is the term used to describe brain degeneration likely caused by repeated head traumas. CTE is a diagnosis made only at autopsy by studying sections of the brain.

https://www.mayoclinic.org/diseases-conditions/chronic-traumatic-encephalopathy/symptoms-causes/syc-20370921

The signs and symptoms of CTE can include:

Cognitive impairment

  • Difficulty thinking (cognitive impairment)
  • Memory loss
  • Problems with planning, organization and carrying out tasks (executive function)

Behavioral changes

  • Impulsive behavior
  • Aggression

Mood disorders

  • Depression or apathy
  • Emotional instability
  • Substance misuse
  • Suicidal thoughts or behavior

Motor symptoms

  • Parkinsonism
  • Motor neuron disease
https://www.mayoclinic.org/diseases-conditions/chronic-traumatic-encephalopathy/symptoms-causes/syc-20370921

Despite receiving more attention recently (at least based on Google web search trends), I am still surprised at how little concern or interest there appears to be among the general public regarding the high rates of CTE observed in profession football players. For example, this study from 2017, which found that:

In a convenience sample of 202 deceased players of American football from a brain donation program, CTE was neuropathologically diagnosed in 177 players across all levels of play (87%), including 110 of 111 former National Football League players (99%).

https://jamanetwork.com/journals/jama/fullarticle/2645104

Or this 2023 study from the Boston University CTE Center which found that 345 out of 376 (91.7 percent) former NFL players had chronic traumatic encephalopathy (CTE). The linked article also provides a helpful comparison to the population of the general public:

For comparison, a 2018 Boston University study of 164 brains of men and women donated to the Framingham Heart Study found that only 1 of 164 (0.6 percent) had CTE. The lone CTE case was a former college football player. The extremely low population rate of CTE is in line with similar studies from brain banks in Austria, Australia and Brazil.

https://www.bumc.bu.edu/busm/2023/02/06/researchers-find-cte-in-345-of-376-former-nfl-players-studied/

It is important to point out that these studies are subject to selection bias since they rely on brains that are donated to brain banks after death:

The NFL player data should not be interpreted to suggest that 91.7 percent of all current and former NFL players have CTE, as brain bank samples are subject to selection biases. The prevalence of CTE among NFL players is unknown as CTE can only be definitively diagnosed after death. 

https://www.bumc.bu.edu/busm/2023/02/06/researchers-find-cte-in-345-of-376-former-nfl-players-studied/

Both of these studies are highly concerning, however, looking at Google Search trends since 2004, interest in the “NFL” vastly exceeds any interest in “CTE” or “Chronic Traumatic Encephalopathy”:

According to statista, NFL revenue has grown every year since 2001, except for 2020, which was an outlier due to the Covid-19 pandemic. NFL revenue in 2001 was 4.28 billion USD and revenue in 2021 was 17.19 billion USD.

Over time I hope to see more research into CTE, including ways to diagnose the disease during life (and subsequently prevent and treat the disease). MRI’s are one technique being investigated to do this, but are not yet ready for clinical use.