The impact of concussion on cardiac autonomic function: A systematic review

<i>Primary objective</i>: To evaluate the evidence regarding the effect of concussion on cardiac autonomic function (CAF). <i>Inclusion criteria</i>: Original research; available in English; included participants with concussion or mild traumatic brain injury (mTBI) and a comparison group; included measures of heart rate (HR) and/or heart rate variability (HRV) as outcomes. Studies of humans (greater than 6 years old) and animals were included. <i>Critical appraisal tools</i>: The Downs and Black (DB) criteria and Structured Effectiveness Quality Evaluation Scale (SEQES). <i>Results</i>: Nine full-length articles and four abstracts were identified. There is conflicting evidence regarding CAF at rest following concussion. There is evidence of elevated HR and reduced HRV with low-intensity, steady-state exercise up to 10 days following concussion. There was no significant difference in HRV during isometric handgrip testing or HR while performing cognitive tasks following concussion. The validity of current literature is limited by small sample sizes, lack of female or paediatric participants, methodological heterogeneity and lack of follow-up. <i>Conclusions</i>: While there is some evidence to suggest CAF is altered during physical activity following concussion, methodological limitations highlight the need for further research. Understanding the effect of concussion on CAF will contribute to the development of more comprehensive concussion management strategies.