Age of First Exposure to Contact and Collision Sports and Later in Life Brain Health: A Narrative Review

Abstract

A controversial theory proposes that playing tackle football before the age of 12 causes later in life brain health problems. This theory arose from a small study of 42 retired National Football League (NFL) players, which reported that those who started playing tackle football at a younger age performed worse on selected neuropsychological tests and a word reading test. The authors concluded that these differences were likely due to greater exposure to repetitive neurotrauma during a developmentally sensitive maturational period in their lives. Several subsequent studies of current high school and collegiate contact/collision sports athletes, and former high school, collegiate, and professional tackle football players have not replicated these findings. This narrative review aims to (i) discuss the fundamental concepts, issues, and controversies surrounding existing research on age of first exposure (AFE) to contact/collision sport, and (ii) provide a balanced interpretation, including risk of bias assessment findings, of this body of evidence. Among 21 studies, 11 studies examined former athletes, 8 studies examined current athletes, and 2 studies examined both former and current athletes. Although the literature on whether younger AFE to tackle football is associated with later in life cognitive, neurobehavioral, or mental health problems in former NFL players is mixed, the largest study of retired NFL players (N = 3,506) suggested there was not a significant association between earlier AFE to organized tackle football and worse subjectively experienced cognitive functioning, depression, or anxiety. Furthermore, no published studies of current athletes show a significant association between playing tackle football (or other contact/collision sports) before the age of 12 and cognitive, neurobehavioral, or mental health problems. It is important to note that all studies were judged to be at high overall risk of bias, indicating that more methodologically rigorous research is needed to understand whether there is an association between AFE to contact/collision sports and later in life brain health. The accumulated research to date suggests that earlier AFE to contact/collision sports is not associated with worse cognitive functioning or mental health in (i) current high school athletes, (ii) current collegiate athletes, or (iii) middle-aged men who played high school football. The literature on former NFL players is mixed and does not, at present, clearly support the theory that exposure to tackle football before age 12 is associated with later in life cognitive impairment or mental health problems.

Association Between Collision Sport Career Duration and Gait Performance in Male Collegiate Student-Athletes

“…One limitation of our study was that career duration was based on participant's self-reported eAFE to collision sports. This approach, though, is consistent with that of previous eAFE studies investigating similar populations, [11][12][13][14]25 as well as studies of older/retired athletes. 25,44,47,48 We were also unable to verify that individuals participated in collision sports continuously from the age that they self-reported, but as both institutions were sponsored NCAA Division I intercollegiate athletic programs, it is highly likely that this approach is accurate, as lengthy breaks in participation would be quite unusual.…”

“…This approach, though, is consistent with that of previous eAFE studies investigating similar populations, 11-14,25 as well as studies of older/retired athletes. 25,44,47,48 We were also unable to verify that individuals participated in collision sports continuously from the age that they self-reported, but as both institutions were sponsored NCAA Division I intercollegiate athletic programs, it is highly likely that this approach is accurate, as lengthy breaks in participation would be quite unusual. Furthermore, we were unable to account for rule differences across our participants’ collision sport history (eg, a participant may have played hockey for 10 years but was allowed full contact/checking for just 8 of those years), so frequent collisions may not have occurred for the entire career duration.…”

“…1,44,47,48 At the collegiate level, recent investigations of healthy NCAA student-athletes found no evidence of an association between estimated age of first exposure (eAFE) and worse outcomes on clinical concussion measures, including neurocognitive function, psychological distress, experienced symptoms, or symptom recovery. [11][12][13][14]25 The relationship between eAFE and functional outcomes has been robustly examined in recent years; however, overall collision sport career duration, as opposed to eAFE, has been recently proposed as the primary diagnostic exposure variable for traumatic encephalopathy syndrome. 26 Overall career duration of collision sports participation may provide a more direct measure of the role of RHIs on functional outcomes versus eAFE, which does not account for number of years of participation.…”

Examining for Cavum Septum Pellucidum and Ventricular Enlargement in Retired Elite-Level Rugby League Players

“…Importantly, in the present study, there were no significant clinical correlations with CSP. Within the retired players group, there were no significant differences between those with vs. without an abnormal CSP and their lifetime exposure to repetitive neurotrauma, measured by the age of their first exposure to rugby league ( 84 ), total number of years of exposure, number of years of elite (professional) play, or number of lifetime concussions. Moreover, there were no significant differences between retired players with vs. without a CSP on measures of depression, impulsivity, perceived cognitive decline, or on any neuropsychological test.…”

Football and Dementia: Understanding the Link

“…The authors propose early exposure to RHI reduced CR and protection against "late life neuropathology" (55). This conclusion has been criticized after a large (>3,550) study of NFL players found no correlation between early age at first tackle with subsequent cognitive performance or behavioral problems (56).…”