Three-year trajectories of disability and fatigue in systemic sclerosis: a cohort study

Objective. Functional disability and fatigue are important consequences of systemic sclerosis (SSc), but little is known about their course over time. The aim of this study was to identify and characterise homogeneous subgroups with distinct 3-year trajectories of disability and fatigue, separately. Methods. A 3-year cohort study including 215 patients with SSc was conducted. Functional disability was assessed using the Health Assessment Questionnaire-Disability Index (HAQ-DI). Fatigue was assessed using the SF-36 Vitality subscale. Longitudinal trajectories were identified using latent class growth analyses (LCGA). Baseline patient characteristics were compared across classes using multivariable logistic regression. Results. Two disability classes were identified: a 'low' group (n=133) with low baseline HAQ-DI scores (intercept=0.48) and slight, statistically non-significant deterioration over time (slope=0.01), and a 'high' group (n=82) with high baseline HAQ-DI scores (intercept=1.63) and also slight, statistically non-significant deterioration over time (slope=0.01). Patients in the high disability group were more likely to be female, have higher fatigue, more helplessness, and less emotion-focused coping. Two fatigue classes were identified: an 'average' group (n=99) with average baseline Vitality scores (intercept=53.9) and slight, statistically non-significant deterioration over time (slope=-0.23), and a 'high' fatigue group (n=116) with low baseline Vitality scores (intercept=39.8) and also slight, but non-significant deterioration over time (slope=-0.15). Patients in the high fatigue group were more likely to be female, report more impact of lung involvement, and less acceptance. Conclusion. Functional disability and fatigue trajectories in SSc were relatively stable over a 3-year period, and differences in baseline scores, but not slopes, defined classes.