Chronic Traumatic Encephalopathy (CTE) is a progressive neurodegenerative disease associated with a history of repetitive head trauma. The inquiry into how common this condition is among high school football players is scientifically complex, as the disease can only be definitively diagnosed after death. Understanding the actual prevalence in this young population requires interpreting limited post-mortem data and focusing on the underlying mechanism of risk. The relationship between years of play, the number of head impacts, and the development of CTE suggests that exposure during adolescence is a serious consideration.
Defining CTE and Diagnostic Limitations
Chronic Traumatic Encephalopathy is a unique tauopathy characterized by the buildup of an abnormal, hyperphosphorylated tau protein in the brain. This protein collects in neurons around small blood vessels, typically concentrated in the cortical folds (sulci). The presence of these specific tau protein tangles causes progressive neurodegeneration, which can lead to symptoms like memory loss, behavioral problems, and difficulties with thinking.
The primary barrier to determining the true prevalence of CTE in any population is the necessity of post-mortem diagnosis. Pathologists must analyze brain tissue after death to confirm the presence and stage of the tau pathology, meaning the condition cannot be diagnosed in a living person. While symptoms in life—such as mood and cognitive issues—can suggest Traumatic Encephalopathy Syndrome (TES), these clinical signs overlap with many other neurological disorders, making a definitive diagnosis impossible without autopsy.
Interpreting Prevalence Data in High School Athletes
Selection Bias in Brain Donation Studies
The most frequently cited data on CTE prevalence comes from studies of brain donations, which are subject to significant selection bias. Families who donate a loved one’s brain often do so because the former player exhibited neurological symptoms while alive. This means the study cohort is not representative of the general population of former high school players, and the reported percentages are likely higher than the true population rate.
Dose-Response Findings
A landmark 2017 study examined the brains of 202 deceased former football players, finding CTE in 177 of them. In that cohort, 3 of 14 former high school players (21 percent) who had only played at the high school level were diagnosed with CTE. This contrasts sharply with the rates found in college players (91 percent) and NFL players (99 percent) in the same study, suggesting a dose-response relationship based on the duration and intensity of play.
Adjusted Risk Estimates
A subsequent analysis attempted to adjust for the selection bias, estimating the cumulative incidence of CTE pathology in men who died between 2008 and 2019 to be at least 5.1 cases per 100,000 deaths among those whose highest level of play was high school. This adjusted analysis suggested that college players had 2.38 times the risk of CTE diagnosis compared to high school players, and professional players had 2.47 times the risk. While the specific numerical prevalence in the general high school population remains unknown, these findings indicate that the risk is lowest for those who only play at the high school level, though the risk is still present.
Cumulative Exposure and Long-Term Risk Factors
The primary driver of CTE risk is the cumulative exposure to repetitive head impacts (RHI) over a career, rather than the number of symptomatic concussions sustained. RHI includes concussive blows and the far more frequent subconcussive impacts, which are hits to the head that do not cause immediate, noticeable symptoms. These smaller, repetitive blows are thought to be sufficient to trigger the pathological process leading to CTE.
Research using helmet-based accelerometer sensors shows that high school football players can sustain an average of 600 subconcussive impacts per season. The total number of years spent playing football is strongly associated with the severity of tau pathology; every additional year of play is linked to a 15% increased odds of a CTE diagnosis. Furthermore, every estimated 1,000 additional head impacts are associated with a 21% increased odds of a CTE diagnosis.
The forces involved in these impacts are also predictive. Models incorporating cumulative linear and rotational acceleration better predict CTE risk than simply counting the number of blows. The adolescent brain may be uniquely vulnerable during this period of rapid development, making the minimization of cumulative head impact exposure a primary goal. Studies show that even without a concussion, high school players can exhibit changes in their brains over the course of a single season due to the accumulation of these subconcussive blows.
Current Strategies for Reducing Head Impact
Efforts to reduce the risk of repetitive head impacts (RHI) at the high school level focus on changing practice methods, improving player technique, and strengthening concussion protocols. Many state high school associations have implemented limitations on full-contact practice time and the frequency of contact drills, which significantly reduce the overall head impact exposure (HIE). Studies show that reducing the number of exercises that require tackling lowers the number of head hits dramatically without affecting team performance.
Coaching education programs, such as “Heads Up Football,” emphasize proper blocking and tackling methods designed to keep the head out of contact. These programs train coaches to ensure players respect the helmet as a protective device rather than a weapon, reinforcing rule changes that penalize helmet-to-helmet contact. Improved concussion management protocols ensure that any player showing signs of head trauma is immediately removed from play and cannot return without medical clearance.
Technological tools, such as helmet sensors, are sometimes used to monitor the frequency and severity of head impacts during practice and games. Although current helmet technology is not designed to prevent concussions, proper fitting and care are emphasized as part of a comprehensive safety strategy. The goal of these combined strategies is to reduce the player’s lifetime cumulative exposure to repetitive head impacts.