Chronic Traumatic Encephalopathy (CTE) is a progressive degenerative brain disease linked to repetitive head trauma. It involves the accumulation of the abnormal tau protein, which disrupts brain function and causes nerve cells to die. Concerns about CTE frequency in high school football players arise because the disease is tied to repeated head impacts, even those that do not result in a diagnosed concussion. Determining CTE prevalence in this population is complex, requiring examination of scientific data and acknowledging limitations in diagnosis. Evidence suggests a relationship between football exposure and CTE risk, but definitive statistics for all high school players remain elusive.
The Challenge of Diagnosing CTE in Living Individuals
The greatest obstacle in determining CTE prevalence is that a definitive diagnosis can only be made after death. CTE is a neuropathological diagnosis, requiring a post-mortem examination of brain tissue under a microscope. Researchers search for the characteristic pattern of tau protein tangles that distinguish CTE from other neurodegenerative diseases like Alzheimer’s.
Clinical symptoms experienced by a living person, such as problems with memory, mood, or impulse control, are often categorized as Traumatic Encephalopathy Syndrome (TES). These symptoms are not unique to CTE and overlap with many other neurological or psychiatric conditions. This overlap means doctors can currently only suspect or monitor for CTE in a living individual, not confirm its presence.
Current research relies on voluntary brain donations, which introduces significant selection bias. Families of former athletes who experienced severe symptoms, such as dementia or dramatic behavioral changes, are far more likely to donate their loved one’s brain. Consequently, the high rates of CTE found in brain bank research do not represent the risk for the general population of athletes.
Interpreting Current CTE Prevalence Data in High School Football
The most widely cited data regarding CTE in football players comes from the Veterans Affairs-Boston University-Concussion Legacy Foundation (VA-BU-CLF) Brain Bank. One major study on autopsied brains found that 3 of 14 high school players, or 21 percent, had evidence of CTE. This finding must be understood within the context of the brain bank’s inherent selection bias, as these were players whose families suspected a problem and actively sought testing.
These studies consistently show a dose-response relationship: the risk and severity of CTE pathology increase with the number of years spent playing football. For example, the same study found CTE in 91 percent of college players and 99 percent of former National Football League (NFL) players. High school players diagnosed with CTE in this research generally showed only the mildest stages of the disease.
When researchers statistically adjusted for selection bias, a 2022 analysis estimated the minimum cumulative incidence of CTE for high school players to be approximately one in 20,000. This calculation is considered a minimum possible rate, with researchers anticipating the actual risk is likely higher. A separate study examining young athletes who died before age 30 found that 41.4 percent of contact sport participants had signs of CTE, reinforcing that the pathology can start early.
Long-Term Risk Factors Beyond Concussions
The development of CTE is not solely linked to the number of diagnosed concussions a high school player sustains. The primary driver appears to be the cumulative exposure to repetitive head impacts (RHI), often called sub-concussive hits. These are blows that do not cause immediate, obvious symptoms but still contribute to the overall burden of trauma over a playing career.
The duration of a football career, measured in total years of play, correlates directly with the pathological severity of CTE found post-mortem. This suggests that the sheer volume of impacts over time is a more significant risk factor than isolated, high-symptom concussions. Playing a position that involves frequent contact, such as an offensive or defensive lineman, also increases the total number of head impacts.
Another significant variable is the age of first exposure (AFE) to tackle football. Research shows that former players who began playing tackle football before age 12 experienced the onset of cognitive and behavioral/mood problems many years earlier than those who started later. Starting before age 12 predicted an earlier onset of cognitive and behavioral symptoms by over 13 years in one study, suggesting a period of vulnerability during early brain development.