Free-living Turning Rather Than Gait Differentiates People with Chronic Mild Traumatic Brain Injury from Controls

Abstract Background: Physical function remains a crucial component of mild traumatic brain injury (mTBI) assessment and recovery. Traditional approaches to assess mTBI lack sensitivity to subtle deficits post-injury, which can impact quality of life, daily function and can lead to chronic issues. Inertial measurement units (IMU) provide an objective alternative for measuring physical function of gait and turning and can be used in any environment. Our recent work has found that turning quality is more sensitive than the quantity of physical activity when comparing chronic mTBI and healthy controls. However, no studies have compared the quality of free-living gait and turning characteristics concurrently in chronic mTBI and healthy controls. This study aimed to determine whether free-living gait or turning is more sensitive in differentiating chronic mTBI from controls.Methods: Thirty-two people with chronic self-reported balance symptoms after mTBI (age: 40.88 ± 11.78 years, median days post injury: 440.68 days) and 23 healthy controls (age: 48.56 ± 22.56 years) were assessed for ~7 days using a single IMU at the waist on a belt. Free-living gait and turning characteristics were evaluated for chronic mTBI and controls using multi-variate analysis. Receiver operating characteristics (ROC) and Area Under the Curve (AUC) analysis were used to determine outcome sensitivity to chronic mTBI.Results: Free-living gait characteristics were not different in chronic mTBI and controls (all p>0.05). In contrast, all but two (number of turns and average velocity CV) free-living turning characteristics were significantly different between chronic mTBI and controls, whilst controlling for age and sex (Bonferroni adjusted p<0.002). The chronic mTBI group had larger turn angles and longer turn durations compared to controls. ROC and AUC analysis showed turn duration (AUC = 0.92) was the most sensitive measure for differentiating chronic mTBI from controls. Conclusions: Results show that turning rather than gait characteristics were significantly different between chronic mTBI and controls, with turn duration being the most sensitive measure. These results suggest turning is a suitable surrogate biomarker to assess and monitor chronic mTBI.