Long-term effects of multiple concussions on prefrontal cortex oxygenation during repeated squat-stands in retired contact sport athletes

Background This study investigated the long-term effects of multiple concussions on prefrontal cortex oxygenation using near-infrared spectroscopy (NIRS) during a squat-stand maneuver that activated dynamic cerebral autoregulation. Methods Active male retired contact sport athletes with a history of 3+ concussions (mTBI; n = 55), and active retired athletes with no concussion history (CTRL; n = 29) were recruited. Participants completed a 5-min squat-stand maneuve (10-s squat, 10-s stand, 0.05 Hz; 15 times). Oxygenated (O(2)Hb), deoxygenated (HHb), total (tHb) hemoglobin, and hemoglobin difference (HbDiff) were analyzed through the change in maximal and minimal values during the test ( increment MAX), Z-scores, and standard deviations. Results mTBI group showed left prefrontal cortex O(2)Hb increment MAX (p = 0.046) and HbDiff increment MAX (p = 0.018) were significantly higher. Within-group analyses showed significantly higher left HHb increment MAX (p = 0.003) and lower left HbDiff Z-scores (p = 0.010) only in the mTBI group. The CTRL group demonstrated significantly lower left HbDiff SD (p = 0.039), tHb Z-scores (p = 0.030), and HbDiff increment MAX (p = 0.037) compared to right prefrontal cortex response. Conclusion These preliminary results suggest changes in prefrontal cortex oxygenation potentially affecting the brain's ability to adapt to changing cerebral perfusion pressure after multiple previous concussions.