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Salivary Cortisol Dynamics After Mild Traumatic Brain Injury
Sophia Musacchio1, Madeline D Kallenbach, Daniel L Huber
1Departments of Neurosurgery (Ms Musacchio, Mx Kallenbach, Mr Huber, and Drs McCrea, Meier, and Nelson) and Medicine, Surgery, and Physiology (Dr Raff), Medical College of Wisconsin, Milwaukee; Endocrine Research Laboratory, Aurora St Luke's Medical Center, Advocate Aurora Research Institute, Milwaukee, Wisconsin (Dr Raff); Department of Kinesiology, Indiana University, Bloomington (Dr Johnson); and UBMD Orthopaedics and Sports Medicine, and SUNY Buffalo Jacobs School of Medicine and Biomedical Sciences, Buffalo, New York (Dr Leddy).
Individuals with mild traumatic brain injury (mTBI) show higher baseline salivary cortisol and increased cortisol response to exercise during recovery. This suggests altered stress hormone regulation following mTBI, impacting rehabilitation.
Area of Science:
- Neuroendocrinology
- Trauma Research
- Sports Medicine
Background:
- Mild traumatic brain injury (mTBI) affects stress hormone regulation.
- Salivary cortisol levels and reactivity are potential biomarkers for mTBI recovery.
- Cognitive and exercise stressors are common during mTBI rehabilitation.
Purpose of the Study:
- To assess mild traumatic brain injury (mTBI)-related alterations in baseline (resting) salivary cortisol.
- To evaluate cortisol reactivity to cognitive and exercise stressors in individuals with mTBI.
- To understand the implications for mTBI rehabilitation and recovery.
Main Methods:
- A prospective cohort study comparing 37 individuals with mTBI and 24 uninjured controls (UCs).
- Saliva samples were collected 10 times across two visits (1 week and 1 month post-injury for mTBI group).
- Cortisol reactivity was assessed using the Paced Auditory Serial Addition Test (cognitive) and Buffalo Concussion Treadmill Test (BCTT, exercise).
Main Results:
- Mean salivary cortisol was significantly higher in the mTBI group compared to UCs at both 1 week and 1 month post-injury.
- The mTBI group exhibited greater cortisol reactivity in response to the BCTT (exercise stressor) at 1 week post-injury.
- No significant mTBI × time interaction was observed for salivary cortisol levels.
Conclusions:
- Elevated salivary cortisol persists into the subacute recovery period (1 week and 1 month) after mTBI.
- Individuals with mTBI show an enhanced cortisol response to aerobic exercise (BCTT) early in recovery.
- Further research is needed to confirm these findings and explore the clinical significance of altered HPA axis responses to exercise in mTBI recovery.
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