Characterizing Patient-Reported Fatigue Using Electronic Diaries in Neurodegenerative and Immune-Mediated Inflammatory Diseases: Observational Study
Background: Fatigue is a prevalent and debilitating symptom in many chronic conditions, including immune-mediated inflammatory diseases (IMIDs) and neurodegenerative diseases (NDDs). Fatigue often fluctuates significantly within and between days, yet traditional patient-reported outcomes (PROs) typically rely on recall periods of a week or more, potentially missing these short-term variations. The development of digital tools, such as electronic diaries (eDiaries), offers a unique opportunity to collect granular, real-time data. However, the #feasibility, adherence, and comparability of eDiary-based assessments to established PROs require further investigation. Objective: This study aimed to evaluate the #feasibility and acceptability of using a high-frequency eDiary to capture intra-day variability in fatigue and to compare eDiary data with scores obtained from the Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-F), a validated weekly recall PRO. Methods: Data were collected from 159 participants enrolled in the IDEA-FAST #feasibility Study; a four-week prospective observational study conducted at four European centres. Participants included individuals with NDDs (n=39), IMIDs (n=78), and healthy volunteers (HVs; n=42). Participants used an eDiary to report their physical and mental fatigue levels up to four times daily on a 7-point Likert scale (0 = low, 6 = high). Adherence was calculated as the proportion of completed eDiary entries relative to the total expected entries. Correlations between averaged eDiary scores and weekly FACIT-F scores were analysed. Results: Adherence to the eDiary protocol was 62% overall, varying by cohort, with the highest adherence (93%) observed in the primary Sjögren’s syndrome (PSS) cohort and the lowest adherence in Parkinson’s disease (PD) (43%) and Huntington’s Disease (HD) (44%) cohorts. The average adherence was 44% in the NDD cohorts and 74% in IMID cohorts. Fatigue levels showed clear diurnal variation, with significantly higher fatigue reported in the evening compared to the morning (p
