Association of body mass index with symptom severity and quality of life in patients with fibromyalgia.

OBJECTIVE: To examine the association between body mass index (BMI) and symptom severity and quality of life (QOL) in patients with fibromyalgia. METHODS: We assessed BMI status and its association with symptom severity and QOL in 888 patients with fibromyalgia who were seen in a fibromyalgia treatment program and who completed the Fibromyalgia Impact Questionnaire (FIQ) and the Short Form 36 (SF-36) health survey. RESULTS: The BMI distribution of nonobese (BMI <25.0 kg/m(2)), overweight (BMI 25.0-29.9 kg/m(2)), moderately obese (BMI 30.0-34.9 kg/m(2)), and severely obese (BMI ≥35.0 kg/m(2)) patients was 28.4% (n = 252), 26.8% (n = 238), 22.2% (n = 197), and 22.6% (n = 201), respectively. Age was significantly different among the 4 groups, with those having a greater BMI being older (P = 0.004). After adjustment for age, group differences were significant in the number of tender points (P = 0.003) and the FIQ and SF-36 scores. The groups with the greater BMI had greater fibromyalgia-related symptoms with worse FIQ total scores (P < 0.001), as well as worse scores in the FIQ subscales of physical function (P < 0.001), work missed (P = 0.04), job ability (P = 0.003), pain (P < 0.001), stiffness (P < 0.001), and depression (P = 0.03). These groups also had poorer SF-36 scores in physical functioning (P < 0.001), pain index (P = 0.005), general health perceptions (P = 0.003), role emotional (P = 0.04), and physical component summary (P < 0.001). Post hoc analysis among the 4 groups showed that differences resided primarily in the severely obese group compared with the other groups. CONCLUSION: In patients with fibromyalgia, severe obesity (BMI ≥35.0 kg/m(2)) is associated with higher levels of fibromyalgia symptoms and lower levels of QOL.