RESUMO
Mild traumatic brain injury (mTBI) is the most common form of TBI, with more than 2.5 million TBI cases in the United States annually. Identification of easily obtainable biomarkers that track strongly with mTBI symptoms may improve our understanding of biological factors that contribute to mTBI symptom profiles and long-term outcomes. Notably, some individuals with mTBI exhibit circadian disruptions and elevated stress sensitivity, which in other clinical groups often correlate with disrupted secretion of cortisol, a glucocorticoid hormone that coordinates circadian and stress physiology. Here, we examined whether cortisol profiles could serve as a biomarker to complement the assessment of neurobehavioral sequelae after mTBI. We partnered with our on-campus health clinic to recruit college students seeking medical care after mTBI (n = 46) and compared this population to a well-matched non-injured student control group (n = 44). We collected data at an initial visit (shortly after injury in mTBI subjects) and one week later. At each visit, we evaluated neurobehavioral function using the Automated Neuropsychological Assessment Metric (ANAM). The subjects also provided cortisol samples through at-home saliva collection. We observed strong coherence between ANAM subjective and objective measures, indicating significant multi-dimensional impairment in subjects with mTBI. Further, female mTBI subjects exhibited diminished neurobehavioral function compared with males. Regardless of sex, decreased amplitude of diurnal cortisol and a blunted cortisol awakening response were associated with mTBI symptom severity and neurobehavioral impairment. Taken together, these findings suggest that salivary cortisol profiles may be a sensitive biomarker for studying underlying biological factors that impact mTBI symptoms and outcomes.
