Physical Activity and Sleep in Chronic Fatigue Syndrome and Fibromyalgia Syndrome: Associations with Symptom Severity in the General Population Cohort LifeLines

Objective. The aim of the current study was to compare physical activity and sleep duration between patients with chronic fatigue syndrome (CFS), patients with fibromyalgia syndrome (FMS), and controls and to examine the association between physical activity level and sleep duration with symptom severity within these patient groups. Methods. This study used data of LifeLines, a general population cohort in which 1.0% (n = 943, 63.7% female, age 44.9 (SD 11.6) years) reported CFS, 3.0% (n = 2, 714; 91.6% female; age 48.4 (SD 10.7) years) reported FMS, and 95.7% (n = 87, 532; 57.9% female; age 44.3 (SD 12.4) years) reported neither CFS nor FMS. Physical activity, sleep duration, and symptom severity were assessed by questionnaires and analysed using ANCOVA and regression analyses, adjusted for age, sex, body mass index, smoking, and educational level. Results. Patients with CFS and FMS had significantly lower physical activity scores (8834 +/- 5967 and 8813 +/- 5549 MET * minutes) than controls (9541 +/- 5533; p < 0.001). Patients with CFS had the longest sleep duration (466 +/- 86 minutes) compared to patients with FMS and controls (450 +/- 67 and 446 +/- 56; p < 0.001). A linear association between physical activity, sleep duration, and symptom severity was only found in controls, in whom higher physical total activity scores and longer sleep duration were associated with a lower symptom severity. In contrast, quadratic associations were found in all groups: both relatively low and high physical activity scores and relatively short and long sleep duration were associated with higher symptom severity in CFS, FMS, and controls. Conclusion. This study indicates that patients with CFS or FMS sleep longer and are less physically active than controls on average. Both low and high levels of physical activity and short and long sleep duration are associated with higher symptom severity, suggesting the importance of patient-tailored treatment.