Tracking daily fatigue fluctuations in multiple sclerosis: ecological momentary assessment provides unique insights

Abstract

Studies investigating the prevalence, cause, and consequence of multiple sclerosis (MS) fatigue typically use single measures that implicitly assume symptom-stability over time, neglecting information about if, when, and why severity fluctuates. We aimed to examine the extent of moment-to-moment and day-to-day variability in fatigue in relapsing-remitting MS and healthy individuals, and identify daily life determinants of fluctuations. Over 4 weekdays, 76 participants (38 relapsing-remitting MS; 38 controls) recruited from multiple sites provided real-time self-reports six times daily (n = 1661 observations analyzed) measuring fatigue severity, stressors, mood, and physical exertion, and daily self-reports of sleep quality. Fatigue fluctuations were evident in both groups. Fatigue was highest in relapsing-remitting MS, typically peaking in late-afternoon. In controls, fatigue started lower and increased steadily until bedtime. Real-time stressors and negative mood were associated with increased fatigue, and positive mood with decreased fatigue in both groups. Increased fatigue was related to physical exertion in relapsing-remitting MS, and poorer sleep quality in controls. In relapsing-remitting MS, fatigue fluctuates substantially over time. Many daily life determinants of fluctuations are similar in relapsing-remitting MS and healthy individuals (stressors, mood) but physical exertion seems more relevant in relapsing-remitting MS and sleep quality most relevant in healthy individuals.

Keywords: Affect; Ambulatory assessment; Ecological momentary assessment; Fatigue; Multiple sclerosis; Psychological stress.

Fig. 1

Step line charts (solid lines) depicting change in Momentary Fatigue Severity ratings in three individuals from the relapsing-remitting MS group over the six assessments (A1–A6) from four assessment days. Dashed lines indicate person-means and dotted lines indicate daily-means. Corresponding within-person indices are presented, including mean, median (med), mean successive squared difference (MSSD; Jahng et al., 2008), probability of acute change (PAC; acute change defined as change ≥5 units between two adjacent assessments; Jahng et al., 2008), and proportion of ratings ≥5

Fig. 2

Average fatigue trajectories over time in the relapsing-remitting MS group (red solid line) and the control group (green dashed line). The circular indicators represent unique Momentary Fatigue Severity assessments in the relapsing-remitting MS group; the triangular indicators represent those in the control group