Persistent musculoskeletal pain in individuals with inflammatory bowel diseases

Abstract

Background: Pain affects over 70% of individuals with inflammatory bowel disease (IBD), with abdominal and musculoskeletal (MSK) pain representing the most common complaints identified by patients. To date most studies in IBD have concentrated on inflammatory arthropathies. However, recent guidelines and investigations suggest that the majority of MSK pain in IBD is likely to be non-inflammatory in nature, although the scope and nature of MSK pain in IBD remains unclear with limited understanding of underlying mechanisms and factors moderating pain experiences. Consequently, further investigation and expanded theoretical frameworks are required in order to develop effective assessment and treatment pathways to improve patient outcomes in this population. Aim: The aim of the present thesis was to explore persistent MSK pain in individuals with IBD, in order to identify shared mechanisms and factors which influence MSK pain experiences in this population. Methods: Two narrative reviews of current literature were conducted to identify fundamental concepts and models in IBD and pain pathways, in order to develop a new framework for persistent MSK pain, primary thesis domains, and thesis methodologies. Two primary thesis studies were used to investigate MSK pain within this framework, including 1) a population-based survey characterizing MSK pain in New Zealand adults through subgrouping and mediation analyses, and 2) a clinic-based investigation investigating measures of central sensitization in American adults with IBD. Results: Subgrouping analysis of Study 1 demonstrated three distinct profiles of MSK pain in individuals with IBD. These profiles indicated that individuals with worse pain experiences presented with greater symptoms related to central sensitization, increased probability of presenting with multiple pain qualities, and active IBD. Sub-analysis of Study 1 further indicated that IBD activity was a significant predictor of worse MSK pain experiences, where symptoms of central sensitization demonstrated significant mediation of this relationship. Study 2 of the present thesis indicated that assessments of somatosensory functioning did not differ between three study groups (i.e. IBD patients with MSK pain, IBD patients without MSK pain, and healthy controls). However, the burden of symptoms related to central sensitization was found to be significantly different between all study groups. Furthermore, Study 2 demonstrated association of measures of central sensitization and a range of participant features (i.e. IBD, psychological, and lifestyle factors). Conclusion: The current thesis presents a new framework to consider and explore persistent MSK pain in IBD patients. Findings from the two primary thesis studies indicated that a sub-population of IBD patients with and without MSK pain presented with features suggesting the presence central sensitization. Individuals with MSK pain and symptoms of central sensitization presented with worse IBD, HRQOL, and pain experiences. MSK pain in IBD presented as distinct profiles, suggesting influences from worse IBD severity to pain presentations and the presence of central sensitization. Measures of central sensitization in IBD were associated with a range of patient features (i.e. IBD, pain, psychological, lifestyle, and comorbidity), highlighting potential risk factors for the development of central sensitization leading to worse pain experiences in IBD patients.