Variability in constraints and functional competence in adults with multiple sclerosis.
OBJECTIVE: Examine intraindividual change in physical and psychological impairments associated with multiple sclerosis and assess the relationship between changes in specific deficits and functional competence in activities of daily living. DESIGN: A multivariate, replicated, single-subject, repeated-measures design was used to examine variability patterns across subjects. Five adults with multiple sclerosis were assessed on leg strength, upright postural control, mood, fatigue, stress, and self-efficacy for 4 mo. Functional competence in three activities of daily living was also evaluated. P-technique factor analyses were performed to examine which variables covaried with time. RESULTS: Analyses revealed covariation among physical and psychological variables for four of the five participants. Across all participants, coefficients of variation revealed greater variability in stress (32.3%-53.4%) and fatigue (23.4%-5.9%) than in any of the physical variables (<20%), and variability in all impairments was greater than variability in the functional tasks (0%-12.6%). CONCLUSIONS: The greater stability in functional performance compared with both physical and psychological constraints provides important insight into symptom management and clinical intervention. The magnitude of variability found in the psychological variables across individuals also has implications concerning psychological adjustment to the disease.