Sport-related concussion induces transient cardiovascular autonomic dysfunction

Recent evidence suggests that concussions may disrupt autonomic cardiovascular control. This study investigated the initial effects of concussion on cardiovascular function using three autonomic reflex tests. Twenty-three recreational athletes (12 women, 11 men) were divided into concussed (n = 12) and control (n = 11) groups. Concussed participants performed forced breathing, standing, and Valsalva autonomic tests four times: 1) within 48 h of injury; 2) 24 h later; 3) 1 wk after injury; and 4) 2 wk after injury. The controls performed the same tests on the same schedule. Differences in heart rate (HR), systolic blood pressure (SBP), and diastolic blood pressure (DBP) responses to the tests were continuously measured using finger photoplethysmography and were analyzed using repeated-measures multivariate ANOVAs and ANOVAs. Within 48 h of injury, the concussed group had significantly greater resting SBP (t₂₁ = 2.44, P = 0.02, d = 1.03), HR (t₂₁ = 2.33, P = 0.03, d = 1.01), and SBP responses to standing (t₂₁ = 2.98, P = 0.01, d = 1.24), and 90% SBP normalization times (t₂₁ = 2.64, P = 0.02, d = 1.10) after the Valsalva, but those group differences subsided 24 h later. There was also a significant interaction with the HR responses to forced breathing (F_3,60 = 4.13, P = 0.01, η_p² = 0.17), indicating the concussed responses declined relative to the control's over time. The results demonstrate that concussion disrupted autonomic cardiovascular control, and that autonomic reflex tests are practical means by which to evaluate that dysfunction.