Evidence of different mediators of central inflammation in dysfunctional and inflammatory pain — Interleukin-8 in fibromyalgia and interleukin-1 β in rheumatoid arthritis

The purpose of this study was to relate central inflammation to autonomic activity (heart rate variability (HRV)) in patients with rheumatoid arthritis (RA) and fibromyalgia (FM). RA patients had reduced parasympathetic activity and FM patients had increased sympathetic activity compared to healthy controls. Comparisons between RA and FM showed higher cerebrospinal fluid (CSF) interleukin (IL)-1β inversely correlated to parasympathetic activity in RA. The FM patients had higher concentrations of CSF IL-8, IL-1Ra, IL-4 and IL-10, but none of these cytokines correlated with HRV. In conclusion, we found different profiles of central cytokines, i.e., elevated IL-1β in inflammatory pain (RA) and elevated IL-8 in dysfunctional pain (FM).