Variability in daily self-reported emotional symptoms and fatigue measured over eight weeks in community dwelling individuals with traumatic brain injury

Objective: To investigate within-person variability in daily self-reported emotional and fatigue symptoms and factors associated with high within-person variability among individuals with chronic traumatic brain injury (TBI). Design: This was a prospective descriptive pilot study of n = 18 adults with chronic TBI (2-27 years post-injury) who owned and could independently use an Apple or Android device. Methods: Participants completed daily assessments for 8 weeks via smartphone. Outcome measures included the Positive and Negative Affect Schedule, Patient Health Questionnaire-2, Generalized Anxiety Disorder-2, and a 7-point fatigue rating. We examined within-person variability over time using individual Multilevel Linear Models. We categorized within-person variability as High or Low based on individual standard deviations in relationship to sample standard deviation. Results: Significant temporal within-person variability occurred for all measures. High variability was associated with more symptom reporting versus Low variability, and variability was associated with sex (High variability: 88% women; Low variability 90% men). Conclusions: Symptom measurement at a single time point among adults with chronic TBI may not capture day-to-day symptom fluctuation and may misidentify individuals in need of intervention. Assessing symptom profiles over time to capture temporal and individual variability may provide a more ecologically valid measure for managing long-term symptoms after TBI.