Pain may be an important factor to consider in inflammatory bowel disease patients troubled by fatigue.

Background: Pain has been associated with fatigue in many chronic diseases, but data are not available for inflammatory bowel disease (IBD). The aim of this study was to investigate whether fatigue is associated with pain in IBD after adjusting for the relevant covariates.

Methods: Participants were recruited from nine hospitals in the south-eastern and western part of Norway. Socio-demographic variables were self-reported by patients. Disease activity was assessed by disease activity indices and faecal calprotectin. Patient-reported outcomes (PROs) were collected using the Fatigue Questionnaire (FQ), Brief Pain Inventory (BPI), Hospital Anxiety and Depression Scale (HADS) and Basic Nordic Sleep Questionnaire.

Results: From a total of 452 invited patients, 414 (91.6%) provided written informed consent. After excluding any missing data, 408 total patients were included in the analyses (ulcerative colitis = 180 and Crohn's disease = 228). In the crude analysis, substantial and chronic fatigue were associated with increased pain intensity regardless of the diagnosis. However, when controlling for relevant covariates in the ANCOVA, the differences in pain intensity among patients with and without substantial or chronic fatigue were insignificant. The Cohen's effect size was small to moderate (>0.20) in patients with chronic fatigue.

Conclusions: Despite a tendency of elevated pain intensity scores among patients with fatigue, these differences were insignificant after controlling for the relevant covariates. However, based on Cohen's effect size, these differences may be of clinical importance in a subset of patients.