In recent years, there has been increasing concern regarding the long-term effects of repetitive head impacts (RHI) sustained by players of contact sports, especially American football.1 Studies have linked RHI exposure to structural and functional changes in the brain in current and former football players of both amateur and professional status, and it has been noted that such alterations may underlie the long-term neuropsychiatric and cognitive deficits observed in some players, including the risk for chronic traumatic encephalopathy that has been observed postmortem in the brains of former players.2-5
However, there is substantial heterogeneity in these findings, and such outcomes were not demonstrated in all players examined. This suggests that “RHI exposure interacts with other risk factors (for example, genetic and environmental) to alter vulnerability to long-term neurological dysfunction,” wrote the authors of a recent study published in Translational Psychiatry.6
They point to age of ﬁrst exposure (AFE) to football as 1 such factor, considering the substantial brain development that occurs during the age range (5-14 years) in which youth football is played. During this period, youth American football players experience a median of 240 to 252 head impacts per season, according to studies using helmet accelerometry.7,8 Other research revealed alterations in the white matter tracts of the left inferior fronto-occipital fasciculus and right superior longitudinal fasciculus in youth aged 8 to 13 years after RHI exposure during a single season of youth football, even without diagnosed concussions.9
Noting the dearth and limitations of existing data on the topic, the authors of the recent study investigated the effects of AFE in a cohort of 214 former amateur and professional football players with no history of other contact sports. Assessments included the Brief Test of Adult Cognition by Telephone, the Behavior Rating Inventory of Executive Function-Adult Version Metacognition Index, the Behavioral Regulation Index, the Center for Epidemiologic Studies Depression Scale, and the Apathy Evaluation Scale.
After controlling for age, education, and duration, the results demonstrated that AFE before age 12 years is associated with >2 times increased odds for clinical impairment on all measures except the Brief Test of Adult Cognition by Telephone, as follows:
- Behavioral Regulation Index: odds ratio (OR), 2.16; 95% CI, 1.19-3.91
- Behavior Rating Inventory of Executive Function-Adult Version Metacognition Index: OR, 2.10; 95% CI, 1.17-3.76
- Center for Epidemiologic Studies Depression Scale: OR, 3.08; 95% CI, 1.65-5.76
- Apathy Evaluation Scale: OR, 2.39; 95% CI, 1.32-4.32
No interaction was observed between AFE and the highest level of play.
These findings seem to suggest that it might be prudent to assess potential players’ vulnerability to these outcomes via a mental health battery. Neurology Advisor recently conducted a poll asking clinicians whether they believed this should be a component of athletic screenings for youth participating in contact sports. Although most respondents answered affirmatively, many indicated that they were unsure of the necessity of such a requirement.
To further explore this topic and the overall state of current knowledge regarding the long-term effect of traumatic brain injury (TBI), Neurology Advisor spoke with experts Christopher C. Giza, MD, professor of pediatric neurology and neurosurgery at the David Geffen School of Medicine and Mattel Children’s Hospital, and director of the University of California, Los Angeles, Steve Tisch BrainSPORT program; and Jennifer M. Coughlin, MD, assistant professor of psychiatry and behavioral sciences at John Hopkins School of Medicine.
Before delving into these issues, said Dr Giza, it is important to differentiate between levels of TBI and head impacts (moderate to severe, mild TBI or concussion, and head impacts with or without injury) and types of cognitive and behavioral impairments that can result from TBI: acute impairment, such as encephalopathy, coma, and amnesia; chronic cognitive and behavioral impairment; exacerbation of underlying preexisting cognitive or behavioral problems; and late-emerging neurobehavioral impairment or dementia/neurodegeneration.
Neurology Advisor: What does current evidence suggest regarding the effect of TBI/head hits on the risk for neuropsychiatric and cognitive impairment?
Dr Giza: There is good evidence from multiple studies that moderate to severe TBI results in cognitive impairments that may partially recover, as well as behavioral and psychiatric problems, some of which emerge later on. There is some evidence that preexisting problems may be worsened by TBI and that moderate to severe TBI may increase risk for late dementia and neurodegeneration.