Do changes in illness perceptions, physical activity, and behavioural regulation influence fatigue severity and health-related outcomes in CFS patients?

OBJECTIVE: Examine to what extent changes in cognitions and changes in physical activity and behavioural regulation patterns influence fatigue severity, physical symptoms, and physical and psychological functioning of patients suffering from Chronic Fatigue Syndrome (CFS) at follow-up.

METHODS: The present study is an observational longitudinal study with a 12-month follow-up. A total of 144 CFS patients participated both at baseline and at follow-up. Four separate hierarchical regression analyses were conducted with fatigue, physical symptoms, physical functioning and psychological functioning at follow-up as the dependent variables, and (changes in) illness perceptions and behavioural regulation patterns (all-or-nothing and limiting behaviour) as the independent variables. Data were collected making use of self-report questionnaires.

RESULTS: Increased Consequence and Identity beliefs over time, as well as increases in all-or-nothing behaviour predicted higher fatigue severity at follow-up. Both number and severity of physical symptoms and psychological functioning at follow-up were only determined by changes in illness perceptions, with increased Consequence beliefs influencing both outcomes, and increased Timeline beliefs only determining physical symptoms. Physical functioning at follow-up was predicted by changes in illness perceptions as well as increased levels of both all-or-nothing and limiting behaviour.

CONCLUSION: The findings point at a differential pattern of associations between changes in illness perceptions and behaviour regulation patterns on the one hand, and patient outcomes on the other hand. Whereas illness perceptions significantly contribute to each of the outcomes, behaviour regulation patterns contribute only to fatigue severity and physical functioning.