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

ABSTRACT

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 (O₂Hb), deoxygenated (HHb), total (tHb) hemoglobin, and hemoglobin difference (HbDiff) were analyzed through the change in maximal and minimal values during the test (∆MAX), Z-scores, and standard deviations.

Results

mTBI group showed left prefrontal cortex O₂Hb ∆MAX (p = 0.046) and HbDiff ∆MAX (p = 0.018) were significantly higher. Within-group analyses showed significantly higher left HHb ∆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 ∆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.

KEYWORDS:

• Concussion
• cerebral autoregulation
• baroreflex
• retired athletes
• prefrontal cortex
• oxygenation

Acknowledgments

The authors would like to sincerely thank all the participants for their time and dedication in support of this data collection. Funding from the Canadian Academy of Sport and Exercise Medicine (CASEM) is gratefully acknowledged. We would also like to thank Cameron Bowers, Jake Bryan, Marisa Harrington, and Kathleen Leahy for their assistance in this project.

Disclosure statement

All authors have no conflicts of interest to declare.

Additional information

Funding

Funding from the Canadian Academy of Sport and Exercise Medicine CASEM Research Grant (CASEM) is gratefully acknowledged