Autonomic Dysregulation in Adolescent Concussion Is Sex- and Posture-Dependent

Objective: To study autonomic responses to postural changes in concussed adolescents. The influence of sex was also studied. Design: Longitudinal cohort observational study. Participants: Concussed adolescents (CONC; n = 65; 26 male adolescents; age 15 +/- 1 years, range = 12-18 years) and a control (CTRL) group of nonconcussed adolescents of similar age and sport (CTRL; n = 54; 29 male adolescents; age 14 +/- 1 years, range = 12-18 years). Interventions: Concussed participants were monitored through 6 weekly visits throughout usual physician care. Control participants underwent 2 visits separated by at least 1 week to account for intrapersonal variation in testing measures. Main Outcome Measures: Heart rate variability as the root mean square of successive differences in R-R intervals (RMSSD), heart rate (HR), and blood pressure [mean arterial pressure (MAP) and diastolic blood pressure (DBP)] were measured in supine, sitting, and standing postures. Results: A mixed analysis of variance revealed a group x sex x posture interaction (P = 0.04) where seated values of RMSSD were less in concussed female participants versus control female participants (42 +/- 4 vs 61 +/- 7 ms; P = 0.01; Mann-Whitney rank test). Compared with CTRL, CONC exhibited increased pretesting seated DBP (69 +/- 1 vs 74 +/- 1 mm Hg; P < 0.01), MAP (83 +/- 1 vs 86 +/- 1 mm Hg; P = 0.02), and baseline seated HR (72 +/- 1 vs 77 +/- 2 bpm; P = 0.03). Values of DBP (P = 0.03) and MAP (P < 0.01) improved at clinical discharge, whereas the RMSSD in female participants did not (P > 0.5). Data are mean +/- SEM. Conclusions: A modest reduction in female cardiac autonomic regulation was observed during seated postures. Alterations in seated concussed DBP and MAP, but not RMSSD, resolved at clinical discharge (median = 37 days). The results indicate that, in adolescents, concussion may impair cardiovagal function in a sex-and posture-dependent manner. The findings also suggest that BP metrics, but not RMSSD, are associated with clinical concussion recovery.