Introduction: The relation between motor and cognitive function and autonomic nervous system (ANS) function during neurorehabilitation following acquired brain injury (ABI) has only been investigated sporadically. In the present study, it was hypothesized that clinical measures in severely injured patients would relate to heart rate variability (HRV), a measure of autonomic function.
Methods: HRV measurements were initially performed on 49 patients (enrolled in a previous study) and follow-up (> 28 days) HRV measurements were performed. Standard deviation of normal-to-normal intervals (SDNN) and low frequency (LF) were extracted and these HRV variables were related to the clinical measures, Early Functional Ability (EFA) and Functional Independence Measure (FIM). Associations between HRV and clinical measures were analysed on admission data (only EFA), at follow-up and for the longitudinal change in measures.
Results: Follow-up HRV was extracted from 19 patients. SDNN and LF were significantly correlated (p < 0.05) to the EFA and FIM at follow-up, but not at admission. SDNN and LF changes were significantly correlated to EFA changes, but not FIM changes. Admission SDNN and LF were unable to provide prognostic information for the EFA and FIM at follow-up.
Conclusion: HRV and its change during neurorehabilitation were associated to EFA and EFA changes over time. Further studies are required to clarify a number of limitations arising from this observational study.