Pain and physical function in patients with spondyloarthritis

Sammanfattning: AbstractAnkylosing spondylitis (AS) and undifferentiated spondyloarthritis (USpA) are two subgroups of the rheumatic disease spondyloarthritis (SpA). The diseases typically debut in early adulthood with periods of fluctuating and persistent pain and stiffness, and can result in consequences such as impaired functioning and reduced quality of life. SpA is a heterogenous group but AS and USpA share many common features. Most evidence is based on studies of men with AS. The aim was to study chronic pain and physical function, including differences betweenAS and USpA, and between men and women, regarding (I) spinal mobility in relation to disease duration, (II) prevalence of chronic widespread pain (CWP), (III) possible risk factors for development of CWP and having persistent CWP, and (IV) different aspects of pain, including pain sensitivity (pain threshold, pain tolerance, and temporal summation of pain).Adult patients with ICD-10 diagnoses corresponding to AS or USpA identified through registers in the Region Skåne, were included in the studies. In Papers I (n=183) and IV (n=226) two clinical cohorts with an axial disease at Skåne University Hospital were studied. In Papers II (n=940) and III (n=712), cross-sectional and longitudinal data from a population-based survey, including patients with AS or USpA were analysed.Patients with SpA showed decreased spinal mobility over time, most evident in AS, and spinal mobility was more severely impaired in the lumbar and thoracic spine in AS compared to USpA. Few differences, between men and women were found, besides anthropometric measures (Paper I). The one-year period prevalence of CWP was 49% in USpA vs. 45% in AS, and more common in females. CWP was associated with female sex, higher BMI and smoking. Men and women with chronic pain reported similar pain intensity, a novel finding (Paper II). Theprevalence of CWP remained high over time, and risk factors for development of, and having persistent CWP included more pain regions, and worse outcomes in health status, disease activity, mental and physical function, and self-efficacy at baseline. Higher age and being female also predicted persistent CWP (Paper III). Patients within the SpA-subgroups reported similar pain sensitivity and pain intensity, but women reported lower pain tolerance, and higher pain intensity compared to men. Lower pain tolerance was associated with worse outcomes in disease activity, fatigue and spinal mobility. In conclusion, concomitant CWP is common in AS and USpA and often persists over time. Together with the finding of impaired spinal mobility in all SpA, these consequences emphasise regular follow-ups, with attention to risk factors for CWP and an early and combinedmanagement with pharmacological and non-pharmacological treatment.