Long-term risk of incident psoriasis in patients with irritable bowel syndrome: a large-scale prospective cohort study

Background: While irritable bowel syndrome (IBS) and psoriasis share some pathophysiological features, it remains unclear whether they are associated with one another. Therefore, we aimed to investigate the long-term risk of incident psoriasis in a large prospective cohort of patients with IBS. Methods: We retrieved data on 437,170 participants from the UK Biobank without psoriasis at baseline. Using ICD-10 codes, we classified these participants into IBS and non-IBS groups based on recruitment status and assessed them for incident psoriasis at follow-ups as the primary outcome. We used multivariable Cox proportional hazards models to estimate adjusted hazard ratios (HRs) and 95% confidence intervals (CIs). Results: We identified 21,748 (5.0%) IBS patients among the 437,170 participants. There were 4325 (1.0%) incident psoriasis cases during a median follow-up period of 14.4 years, amounting to a cumulative incidence of 0.88% (95% CI = 0.73-1.02) in the IBS group vs. 0.69% (95% CI = 0.66-0.72) in the non-IBS group. Compared with non-IBS patients, patients with IBS had a 35.0% higher risk of developing psoriasis (HR = 1.35; 95% CI = 1.19-1.52). In subgroup analyses, a higher psoriasis risk associated with IBS was generally observed across age, sex, Townsend deprivation index, smoking status, non-steroidal anti-inflammatory drug use, C-reactive protein, and polygenic risk score of psoriasis subgroups. Conclusions: The IBS patients in our sample had an increased long-term risk of incident psoriasis. This finding highlights the importance of monitoring psoriasis in IBS patients and suggests a potential shared pathophysiological mechanism between the two conditions which may inform future preventive and therapeutic strategies.