Central sensitivity and fibromyalgia: a discriminating construct within different chronic pain conditions

Background. Fibromyalgia (FM) is a chronic pain (CP) syndrome; FM patients often suffer from multiple CP comorbidities, mainly: tension-type headache or migraine, irritable bowel syndrome, and low back pain. The IASP defines Central Sensitivity (CS) as an increased responsiveness of nociceptive neurons in the central nervous system to normal or subthreshold inputs. While international literature connects CS to psychological burdens in CP conditions like FM and chronic headache (CH), there`s limited exploration comparing FM patients with and without other CP comorbidities. Objective. To investigate whether CS discriminates between FM patients, those with different CP comorbidities, and healthy controls (HCs). Methods. 944 women participated (n=240 CH; n=204 FM; n=376 FM with comorbidities; n=124 HCs) and completed an online self-administered protocol, including the Central Sensitivity Inventory and socio-anamnestic information. A general linear model ANCOVA, covarying for age, tested CSI score differences. Results. Data analysis showed a good fit of the model (R2 Adjusted =0.340; df=4; F=116; p=0.001) and a significant difference between groups in CSI scores (p=0.001). Post-hoc test showed that all the clinical groups scored significantly higher than HCs (all p=0.001); FM and FM with comorbidities scored significantly higher than CH (both p=0.001). FM with comorbidities scored higher than FM alone (p=0.015), indicating the highest scores among groups. Conclusion. CS appears to play a discriminating role among CP conditions, especially in FM with other CP comorbidities. Integrating CS assessment in the clinical evaluation of CP patients could enhance understanding of the complex connection between CP and mental health.