Study Shows Mileage Matters When It Comes to Brain Health and Contact Sports

Adding to the growing medical literature connecting Chronic Traumatic Encephalopathy (“CTE”) and exposure to contact sports an important study was published this week in the Annals of Neurology finding that for every year an individual plays football their chances of developing the brain disease increases by 30%.

In the study, titled Duration of American Football Play and CTE, the authors sampled 266 brains of deceased American football players.  223 of 266 participants met the criteria for a diagnosis of CTE.  Data revealed the amount of years playing football was connected to the likelihood of developing the disease and to the severity of symptoms.   The data revealed that the odds of CTE double every 2.6 years of football played.

The lesson a study such as this can teach those in combat sports, or any contact sport for that matter, is that mileage matters.  Cumulative brain trauma takes its toll.  The more years of exposure the greater the risk.  Those looking to pursue a career in combative sports should appreciate this reality when mapping out their career path and considering an exit strategy.

The study’s full abstract reads as follows:



Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease associated with exposure to contact and collision sports, including American football. We hypothesized a dose‐response relationship between duration of football played and CTE risk and severity.


In a convenience sample of 266 deceased American football players from the Veterans Affairs‐Boston University‐Concussion Legacy Foundation and Framingham Heart Study Brain Banks, we estimated the association of years of football played with CTE pathological status and severity. We evaluated the ability of years played to classify CTE status using receiver operating characteristic curve analysis. Simulation analyses quantified conditions that might lead to selection bias.


223 of 266 participants met neuropathological diagnostic criteria for CTE. More years of football played was associated with having CTE (odds ratio [OR]=1.30 per year played, 95%CI, 1.19‐1.41; P=3.8×10‐9) and with CTE severity (severe vs. mild; OR=1.14 per year played, 95%CI, 1.07‐1.22; P=3.1×10‐4). Participants with CTE were 1/10th as likely to have played <4.5 years (negative likelihood ratio [LR]=0.102, 95%CI, 0.100‐0.105) and were 10X as likely to have played >14.5 years (positive LR=10.2, 95%CI, 9.8‐10.7) compared with participants without CTE. Sensitivity and specificity were maximized at 11 years played. Simulation demonstrated that years played remained adversely associated with CTE status when years played and CTE status were both related to brain bank selection across widely ranging scenarios.


The odds of CTE double every 2.6 years of football played. After accounting for brain bank selection, the magnitude of the relationship between years played and CTE status remained consistent.

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