Real-World Epidemiology of Inflammatory Bowel Disease in Italy: Treatment Patterns, Adherence, and Costs in Patients with Ulcerative Colitis Treated with Mesalazine.

Abstract

Ulcerative colitis (UC) and Crohn's disease (CD) are chronic immune-mediated conditions associated with a substantial clinical and economic burden. Italian epidemiological evidence is limited. Mesalazine remains a cornerstone of UC management. This study aimed to provide updated epidemiological estimates of inflammatory bowel disease (IBD) in Italy, and to evaluate real-world treatment patterns, adherence to oral mesalazine, and healthcare costs among patients with UC initiating mesalazine therapy. A retrospective observational analysis was conducted using Italian administrative databases covering ~4 million beneficiaries. Patients with UC and CD were identified (January 2010-May 2023) using the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) or exemption codes. Patients with UC who were new users of mesalazine were characterized at baseline. Mesalazine treatment patterns, adherence, and direct healthcare costs were described at follow-up. At the end of 2023, UC and CD prevalence rates were 272 (95% confidence interval [CI] 267-278) and 166/100,000 (95% CI 162-170) inhabitants, respectively. Incidence rates in 2023 of UC and CD were 18.9 (95% CI 18-20) and 10.8/100,000 (95% CI 10-12), respectively. Among 2552 patients with UC who were new mesalazine users, 69.6% of time-dependent mesalazine users were adherent (versus 56.1% pH-dependent users). Mean annual cost per patients with UC who were new mesalazine users in 2023 was €4516, mainly driven by hospitalizations. This real-world analysis provides recent epidemiological estimates of UC and CD, and describes a substantial economic burden, highlighting the need for improving adherence and therapeutic pathways.