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. 2023 Jul-Aug;38(4):E318-E327.
doi: 10.1097/HTR.0000000000000855. Epub 2023 Jan 21.

Salivary Cortisol Dynamics After Mild Traumatic Brain Injury

Sophia Musacchio  1 , Madeline D Kallenbach, Daniel L Huber, Hershel Raff, Blair D Johnson, John Leddy, Michael A McCrea, Timothy B Meier, Lindsay D Nelson
Affiliations

Salivary Cortisol Dynamics After Mild Traumatic Brain Injury

Sophia Musacchio et al. J Head Trauma Rehabil. 2023 Jul-Aug.

Abstract

Objective: To assess mild traumatic brain injury (mTBI)-related alterations in baseline (resting) salivary cortisol and cortisol reactivity to cognitive and exercise stressors, which are frequently encountered during mTBI rehabilitation and recovery.

Setting: Persons with mTBI were recruited from a level 1 trauma center emergency department. Uninjured controls (UCs) were recruited from the community.

Participants: Participants were 37 individuals with mTBI and 24 UCs. All patients with mTBI were enrolled at 7 ± 3 days post-injury, met the American Congress of Rehabilitation Medicine definition of mTBI, and had no acute intracranial findings on clinical neuroimaging (if performed).

Design: A prospective cohort study design was used. All participants provided saliva samples 10 times during each of 2 visits spaced 3 weeks apart (1 week and 1 month post-injury for the mTBI group). Each visit included baseline saliva sampling and sampling to evaluate reactivity to a cognitive stressor (Paced Auditory Serial Addition Test) and physical stressor (Buffalo Concussion Treadmill Test [BCTT]).

Main outcome measure: Natural log-transformed salivary cortisol was measured by enzyme immunoassay. Cortisol was predicted using a linear mixed-effects model by group (mTBI and UC), visit (1 week and 1 month), and saliva sample.

Results: Mean salivary cortisol was higher in the mTBI group (1.67 nmol/L [95% CI 1.42-1.72]) than in controls (1.30 nmol/L [1.12-1.47]), without an mTBI × time interaction. At 1 week, the mTBI group had greater cortisol reactivity in response to the BCTT.

Conclusions: Higher cortisol in individuals with mTBI at 1 week and 1 month post-injury extends previous findings into the subacute recovery period. Furthermore, the mTBI group demonstrated a greater cortisol response to mild-to-moderate aerobic exercise (BCTT) at 1 week post-injury. Given the increasing role of exercise in mTBI rehabilitation, further research is warranted to replicate these findings and identify the clinical implications, if any, of enhanced hypothalamic-pituitary-adrenal axis responses to exercise in civilians with recent mTBI.

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Conflict of interest statement

The authors declare no conflicts of interests.

Figures

Figure 1.
Figure 1.
Visit timeline. The Cognitive Task reflected a modified version of the Paced Auditory Serial Addition Test (PASAT). The Treadmill Task reflected the Buffalo Concussion Treadmill Test (BCTT).
Figure 2.
Figure 2.
Mean salivary cortisol levels by Group, Visit, and Sample Number. Linear mixed effects modeling demonstrated a significant main effect of group due to higher cortisol levels in the mTBI versus the uninjured control group, as well as a significant Visit x Sample interaction due to changes (decreases) in cortisol across samples at Visit B that were not significant at Visit A.
Figure 3.
Figure 3.
Change in salivary cortisol due to exercise on the Buffalo Concussion Treadmill Test.
See this image and copyright information in PMC

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