Background:The inflammatory bowel disease (IBD) disability index has recently been introduced to measure patients' physical, psychological, familial, and social limitations associated with IBD. We assessed factors related to self-reported disability and the relationship between disability and direct health care costs.Methods:A large cohort of patients with Crohn's disease (CD) and ulcerative colitis (UC) was prospectively followed for 2 years by 3 monthly web-based questionnaires. At 2 years, patients completed the IBD disability index, with lower score indicating more disability. Linear regression analysis was used to examine the impact of demographics, clinical characteristics, and illness perceptions on self-reported disability. Trends in direct health care costs across the disability severity groups minimal, mild, moderate, and severe, were tested.Results:A total of 554 patients with CD and 424 patients with UC completed the IBD disability index (response rate, 45%). Both clinical characteristics and illness perceptions significantly contributed to self-reported disability (45%-47%, P = 0.000 and 8%-12%, P = 0.000, respectively). Patients with CD scored lower on the self-reported IBD disability index than patients with UC (0.255 versus 3.890, P <0.000), indicating more disability in patients with CD. Factors independently associated with higher self-reported disability rates were increased disease activity, illness identity (higher number of symptoms attributed to IBD), and stronger emotional response. Disease duration and disease phenotype were not associated with self-reported disability. Direct health care costs increased with the worsening of self-reported disability (P = 0.000).Conclusions:More disability was reported by patients with CD than by UC. Self-reported disability in IBD was mainly determined by clinical disease activity and illness perceptions but not by disease duration or disease phenotype.