Glymphatic system dysfunction associated with player position in collegiate American football players: A DTI-ALPS study.

Purpose: The glymphatic system plays a crucial role in both short-term and long-term brain health through the clearance of neural waste and is vulnerable to disruption following head trauma. This study aimed to determine whether exposure to a season of sub-clinical head acceleration events (HAEs) in collegiate American football affects glymphatic function, and whether this effect varies by player position or concussion history. Methods: Sixty-six male NCAA Division I football athletes underwent diffusion tensor imaging (DTI) before and after a competitive football season. Glymphatic function was quantified using the Diffusion Tensor Imaging Along the Perivascular Space (DTI-ALPS) index. Participants were categorized by player position (Speed vs. Non-Speed) and concussion history (Yes vs. No). Linear mixed-effects models were used to evaluate changes in DTI-ALPS index by time point, hemisphere, position, and concussion history. Results: There were no significant changes in DTI-ALPS values from pre-to post-season in either hemisphere across the full cohort. However, a significant main effect of player position was observed in the right hemisphere (p = 0.025), with Speed position players demonstrating lower DTI-ALPS indices compared to Non-Speed players, suggesting reduced glymphatic function. No significant effects of concussion history or interaction terms were found. Conclusions: These findings indicate that positional differences in HAEs experienced by Speed players, even absent clinical concussion, may contribute to impaired glymphatic function. Speed position players may be at increased risk due to the nature and magnitude of head impacts. The DTI-ALPS index may serve as a sensitive biomarker for early, sub-clinical brain dysfunction in athletes participating in contact sports.