Abstract
A substantial number of people experience persistent post-concussion symptoms (PPCS) following a concussion. Traditional retrospective assessments, such as the Rivermead Post Concussion Symptoms Questionnaire (RPQ), are prone to memory biases and do not capture the day-to-day variability of PPCS. In this study, we explored the association between daily registrations of PPCS and the RPQ. We also examined the variability of PPCS trajectories over time. Nineteen participants registered PPCS symptoms for 28 days using an mHealth app and then completed the RPQ. From the final 7 days, average, highest, and last-day symptom scores were calculated and correlated with corresponding RPQ items. Scores from the full 28-day period were used to compute the within-person standard deviation and mean squared successive difference (MSSD) for each symptom that participants rated as the most bothersome. Correlations between the RPQ and daily registrations were weak-to-medium (range: 0.343, 0.590). The retrospective RPQ explained up to 35% of the variance in average daily registrations of PPCS. The MSSD ranged from 0 to 16.29, and the within-person SD from 0 to 3.25. Visual analyses showed that participants with identical RPQ item scores often exhibited different PPCS variability. This was also true for different symptoms within the same participant. This study highlights the potential additional value of daily registrations for capturing the dynamic and fluctuating nature of PPCS, which may be missed by retrospective questionnaires administered at one time point. PPCS vary both within and between individuals over time and reducing this complexity to a single total score oversimplifies a nuanced reality. Larger studies are needed to confirm these findings, and future work should investigate the clinical relevance of capturing daily variations in PPCS.