Decreased physical activity attributable to higher body mass index influences fibromyalgia symptoms.

BACKGROUND Although previous studies report associations between increased body mass index (BMI) and fibromyalgia symptoms, there is uncertainty as to whether this relationship is driven by physical factors, psychological factors, or both. OBJECTIVE To assess these relationships in a clinical sample of patients with fibromyalgia. DESIGN Cross-sectional study. SETTING Tertiary care facility. PATIENTS A total of 686 patients from an existing national fibromyalgia registry. METHODS Patients completed a demographic form and self-report questionnaires including the Fibromyalgia Impact Questionnaire-Revised (FIQ-R), the Medical Outcomes Study Short Form-36 (SF-36), the Brief Pain Inventory (BPI), and the 30-item Profile of Mood States (30-item POMS). MAIN OUTCOME MEASUREMENTS FIQ-R overall impact subscale. RESULTS BMI was significantly correlated with fibromyalgia impact (P < .001). The relationship between BMI and fibromyalgia impact was almost fully accounted for by physical factors and not by psychological factors. CONCLUSIONS Despite patient report that pain hinders physical activity, clinicians who encounter patients with fibromyalgia, particularly patients with increased BMI, should be cognizant of the need to invest time and resources to counsel patients on physical factors (ie, physical activity) that could improve the patients' symptom experience.