Mild Traumatic Brain Injury Is Associated with Increased Dual-Task Cost during Ambulation: A Preliminary Study

Objective The aim of the study was to determine the impact of dual-task conditions on mobility after mild traumatic brain injury. Design Eleven adults with mild traumatic brain injury within 1 wk of injury and 10 age- and sex-matched healthy controls completed gait trials with a single-task condition and three separate dual-task conditions: counting by 1 (low), serial subtraction by 3 (medium), and alternating letters and numbers (high). Dual-task cost was calculated as dual-task cost = ([dual-task performance] - [single-task performance]) / [single-task performance] × 100%. Results Participants with mild traumatic brain injury ambulated slower than control subjects (P < 0.001). Significant differences in dual-task cost were noted for both group (P < 0.001) and dual-task condition (P = 0.005). Dual-task cost was greater for those with mild traumatic brain injury compared with controls with significant group differences for the low and high cognitive loads (P < 0.05). Only 1 of the 11 individuals with mild traumatic brain injury and 1 of the 10 controls demonstrated gait speed less than 80 cm/sec, which is predictive of community mobility, during any dual-task condition. Dual-task cost exceeded 11.9%, previously determined to be the minimal detectable change in healthy adults, for 9 of the 11 individuals with mild traumatic brain injury compared with 3 of the 10 controls. Conclusions Dual-task cost may be a more sensitive measure for impairment during dual-task conditions than gait speed after mild traumatic brain injury.