Recall measures overlook information about daily life experience: a focus on fatigue in multiple sclerosis

Abstract

Background: Understanding and alleviating symptoms is an important area of research in health psychology. Traditionally, researchers use a recall questionnaire covering a prescribed time-period to obtain a single rating for each participant, assuming symptom-constancy over time and ignoring within-individual fluctuations. We tested the relative extent of within-individual moment-to-moment and day-to-day variability in fatigue, typical daily patterns of fatigue over time, and explored the utility of within-person patient reported outcomes (PROs) as indicators of the dynamic symptom experience. Methods: Over 4 days, 38 people with relapsing-remitting multiple sclerosis (RRMS) and 38 healthy controls provided six real-time assessments of fatigue severity (ratings from 0–10) per day. Analysis was by multilevel modelling. Results: Typical daily fatigue patterns in RRMS increased by 0.49 units/hr (p < .001) with a simultaneous decrease of 0.03 units/hr2 (p = .012): a quadratic trajectory generally peaking in mid-afternoon. Healthy individuals started lower and increased steadily by 0.27 units/hr until bedtime (p = .015). Random time effects (ps < .001) revealed substantial differences in fatigue patterns from individual-to-individual and day-to-day. Notably, several participants with similar person-means had vastly different within-person PROs, including mean successive squared differences and estimated probabilities of acute change (measuring the probability of a change of ≥ 5 units from one assessment to the next). Conclusion: Understanding how symptoms are dynamically experienced by each individual may present opportunities to further develop tailored interventions. Assessing the relative importance of within-person aspects of symptom experience to quality of life may inform novel means of evaluating treatment efficacy.