Global switch cost as an index for concussion assessment: reliability and stability.

PURPOSE: The objective of this study is to determine the stability and sensitivity of a dual-task (DT) methodology that can be used to assess the effects of concussion in athletes.

METHODS: Fifty-nine healthy young adults (Mage = 20.32 ± 1.84 yr, 19 males) who volunteered to participate completed auditory switch tasks that varied in length (30, 40, and 60 items) at baseline, 1 wk later, and approximately 7 months later. During sessions 2 and 3, the participants completed one of three switch tasks while concurrently performing a modified Harvard Step Test. Global switch cost indices and percentage error were calculated for each switch task. The stability reliability of the global switch cost indices was assessed under single-task conditions, and the sensitivity of the global switch costs to interference effects was assessed under DT conditions.

RESULTS: The stability reliability was 0.64, 0.84, and 0.83 for the 30-, 40-, and 60-item tests, respectively. ANOVA revealed a main effect for condition (single task vs DT) for both global switch costs (F(1,55) = 44.53, P < 0.0001) and percentage error (F(1,56) = 64.69, P < 0.001). The magnitude of the global switch cost interference effects was nearly identical across the three DT conditions.

CONCLUSIONS: The current concussion testing models test athletes' cognitive and physical function in isolation. The stability reliability of the global switch cost index obtained under DT conditions suggests that it may be a useful measure for clinicians. The DT paradigm presents another test methodology that may be useful for making return-to-play decisions as part of a comprehensive concussion management plan.