Serum interleukin-6 in primary fibromyalgia syndrome patients: Impact on disease burden, severity, quality of life and sleep

To assess serum interleukin-6 (IL-6) level in primary fibromyalgia syndrome (FMS) patients and to study its relation to disease burden parameters Forty primary FMS patients and 40 age and sex matched controls were studied. Patients answered multiple questionnaires. Fatigue was assessed by multidimensional fatigue inventory (MFI-20), pain severity by visual analogue scale (VAS-pain) and sleep quality by sleep quality numerical rating scale (NRS). The 36-Item Short Form (SF-36) was used to assess quality of life and fibromyalgia Impact Questionnaire (FIQ) was used to evaluate patient status, progress and outcomes. The patients mean age was 36.5 ± 7.1 years and disease duration 5.3 ± 2.95 years and they were 38 females and 2 males. The mean serum IL-6 level was significantly higher in patients (134.9 ± 67.3 pg/ml) than control (41.1 ± 8.5 pg/ml)(p = 0.001). The mean VAS-pain was 6.2 ± 1.3 (4–8), FIQ was 58 ± 6.1 (50–70), SF-36 47 ± 10.2 (30–60), MFI20 was 76.5 ± 10.6 (60–95) and sleep quality NRS was 6.9 ± 1.2 (5–9). The values of the studied parameters and scores were significantly different from the control 1.4 ± 0.5; 14.4 ± 6.5; 93.9 ± 3.5 10 ± 5.2 and 0.9 ± 0.8 respectively; p = 0.001 for all). There was a significant correlation between serum IL-6 levels and VAS-pain (r = 0.72, p = 0.001), FIQ (r = 0.58, p = 0.001), SF-36 (r = 0.78, p = 0.001), MFI-20 (r = 0.74, p = 0.001) and sleep NRS (r = 0.78,p = 0.001). On regression, IL-6 level had a greater impact on sleep NRS (p = 0.001), SF-36 (p = 0.005) and MFI20 (p = 0.01). Serum IL-6 level is high in primary FMS patients. Also, serum IL-6 is significantly related to the parameters of fatigue, functional status, sleep quality and pain.