Balance Regularity Among Former High School Football Players With or Without a History of Concussion

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 X 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 (F-2,F-40 = 3.26, P = .049, eta(2)(p) = 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; t(20) = -2.48, P = .02), but conditions 4 (mean difference = -0.11; 95% CI: -0.37, 0.15; t(20) = -0.86, P = .40) and 6 (mean difference = -0.25; 95% CI: -0.55, 0.06; t(20) = -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.