Factors associated with the inflammatory process in pain in ankylosing spondylitis

INTRODUCTION: sleep disorders, closely related to any chronic pain process, are frequent among patients with rheumatic diseases, mainly ankylosing spondylitis (AS). Our study aimed to determine the association between sleep disturbances and the inflammatory process in pain in AS patients compared with lower back pain (LBP) patients. We have additionally examined factors associated with sleep disorders among AS patients. METHODS: we conducted a cross-sectional study among AS patients. Sociodemographic data, patient reported outcomes and disease characteristics were recorded. Sleep was assessed using the medical outcomes study sleep scale measure (MOS-SS). For psychological assessment, Beck anxiety (BAI) and depression index (BDI) was used. A multivariate logistic regression was performed to identify factors associated with sleep disorders. RESULTS: the study included 50 patients with AS and 40 patients with low back pain. The most common affected domains among AS patients were inadequacy, sleep disturbance, and daily somnolence. The MOS-SS index was significantly higher in the AS group than in the control group (p<0.001). Sleep disorder was associated with age, female gender, analphabetism, patient-reported outcomes (all p<0.05), but was not associated with profession, comorbidities and smoking habits. In multivariate analysis, factors associated with sleep disruption were the duration of morning stiffness (MS), disease activity, bath ankylosing spondylitis metrology index (BASMI), ASQol, as well as anxiety and depression (odds ratio: 5.4(CI 95% 1.6-18.3), 9.9 (CI95%1.1-86); 6 (CI95%1.1-32); 13 (CI 95% 1.4-143.8); 15.7 (CI 95% 2.6-94.3); 14 (CI 95% 2-105.7) respectively, p<0.05 for each). CONCLUSION: our study highlighted the importance of sleep disorders among patients with AS with a predilection for inadequacy, sleep disturbance, and daily somnolence. Factors associated with sleep disruption were high disease activity, a longer duration of MS, an altered function and quality of life as well as anxiety and depression.