Abstract

Context: Subclinical postural-control changes may persist beyond the point when athletes are considered clinically recovered postconcussion.
Objective: To compare postural-control performance between former high school football players with or without a history of concussion using linear and nonlinear metrics.
Design: Case-control study.
Setting: Clinical research laboratory.
Patients or Other Participants: A total of 11 former high school football players (age range, 45–60 years) with 2 or more concussions and 11 age- and height-matched former high school football players without a history of concussion. No participant had college or professional football experience.
Main Outcome Measure(s): Participants completed the Sensory Organization Test. We compared postural control (linear: equilibrium scores; nonlinear: sample and multiscale entropy) between groups using a 2 × 3 analysis of variance across conditions 4 to 6 (4: eyes open, sway-referenced platform; 5: eyes closed, sway-referenced platform; 6: eyes open, sway-referenced surround and platform).
Results: We observed a group-by-condition interaction effect for medial-lateral sample entropy (F2,40 = 3.26, P = .049, ηp2 = 0.140). Participants with a history of concussion presented with more regular medial-lateral sample entropy values (0.90 ± 0.41) for condition 5 than participants without a history of concussion (1.30 ± 0.35; mean difference = −0.40; 95% confidence interval [CI] = −0.74, −0.06; t20 = −2.48, P = .02), but conditions 4 (mean difference = −0.11; 95% CI: −0.37, 0.15; t20 = −0.86, P = .40) and 6 (mean difference = −0.25; 95% CI: −0.55, 0.06; t20 = −1.66, P = .11) did not differ between groups.
Conclusions: Postconcussion deficits, detected using nonlinear metrics, may persist long after injury resolution. Subclinical concussion deficits may persist for years beyond clinical concussion recovery.