Factor structure of the Rivermead Post-Concussion Symptoms Questionnaire over the first year following mild traumatic brain injury

Background: We examined the factor structure of the Rivermead Post-Concussion Symptom Questionnaire (RPQ), the most commonly used measure of post-concussive symptoms, over the first year post-injury.Method: Factor analysis (orthogonal rotation) was used to examine the RPQ items that form coherent subsets/factors within 2-weeks, and 1, 6, and 12-months post-mTBI in 527 adults (age >16years).Results: At baseline, three factors accounted for 63.95% of the variance; factor 1 reflected cognitive and physiological disturbances; factor 2 included items reflecting mood, sleep, and nausea/vomiting; and factor 3 included visual/auditory disturbances, dizziness, and headaches. At 1 month, three factors were again extracted (63.26% variance). Factor 1 reflected cognitive and mood symptoms, factor 2 reflected mood with headache, nausea, and dizziness; and factor 3 reflected visual disturbances. Two factors were obtained at 6 and 12 months (63.7% and 63.38% of variance): factor 1 included mood/cognitive items, restlessness, sleep disturbance, and noise sensitivity; whereas, factor 2 included physiological symptoms.Conclusions: The factor structure of the RPQ changes over time; however, it was relatively stable from 6 to 12-months post-injury. Subject to further evaluation, assessments conducted from 6 months could consider using these two factors as subscales. Changing the factor structure of RPQ before 6 months suggests that timing of assessment should be considered in applying these factors.