Relationship of collegiate football experience and concussion with hippocampal volume and cognitive outcomes

IMPORTANCE: Concussion and subconcussive impacts have been associated with short-term disrupted cognitive performance in collegiate athletes, but there are limited data on their long-term neuroanatomic and cognitive consequences. OBJECTIVE: To assess the relationships of concussion history and years of football experience with hippocampal volume and cognitive performance in collegiate football athletes. DESIGN, SETTING, AND PARTICIPANTS: Cross-sectional study conducted between June 2011 and August 2013 at a US psychiatric research institute specializing in neuroimaging among collegiate football players with a history of clinician-diagnosed concussion (n = 25), collegiate football players without a history of concussion (n = 25), and non-football-playing, age-, sex-, and education-matched healthy controls (n = 25). EXPOSURES: History of clinician-diagnosed concussion and years of football experience. MAIN OUTCOMES AND MEASURES: High-resolution anatomical magnetic resonance imaging was used to quantify brain volumes. Baseline scores on a computerized concussion-related cognitive battery were used for cognitive assessment in athletes. RESULTS: Players with and without a history of concussion had smaller hippocampal volumes relative to healthy control participants (with concussion: t₄₈ = 7.58; P < .001; mean difference, 1788 μL; 95% CI, 1317-2258 μL; without concussion: t₄₈ = 4.35; P < .001, mean difference, 1027 μL; 95% CI, 556-1498 μL). Players with a history of concussion had smaller hippocampal volumes than players without concussion (t₄₈ = 3.15; P < .001; mean difference, 761 μL; 95% CI, 280-1242 μL). In both athlete groups, there was a statistically significant inverse relationship between left hippocampal volume and number of years of football played (t₄₆ = -3.62; P < .001; coefficient = -43.54; 95% CI, -67.66 to -19.41). Behavioral testing demonstrated no differences between athletes with and without a concussion history on 5 cognitive measures but did show an inverse correlation between years of playing football and reaction time (ρ₄₂ = -0.43; 95% CI, -0.46 to -0.40; P = .005). CONCLUSIONS AND RELEVANCE: Among a group of collegiate football athletes, there was a significant inverse relationship of concussion and years of football played with hippocampal volume. Years of football experience also correlated with slower reaction time. Further research is needed to determine the temporal relationships of these findings.