Incidence and Risk of Inflammatory Bowel Disease in Patients with Psoriasis-A Nationwide 20-Year Cohort Study

In psoriasis patients, incidence rates of Crohn disease (CD) and ulcerative colitis (UC) have been increased in epidemiological studies and certain clinical trials, yet the association remains poorly understood. We studied a 20-year nationwide cohort of 235,038 Danish adults with psoriasis and a 1: 1 matched reference group. Less than 1% of psoriasis patients developed CD or UC during follow-up. Incidence rates of CD were highest for younger women with psoriasis and patients with concurrent psoriatic arthritis, whereas men with psoriasis had particularly high incidence rates of UC compared with their non-psoriasis peers. Adjusted hazard ratios of CD were 1.84 (95% confidence interval [CI] = 1.47-2.29) and 2.38 (95% CI = 1.62-3.49) among psoriasis patients treated with topical and systemic nonbiologic therapy, respectively. No definite CD cases occurred during biologic therapy. For UC, adjusted hazard ratios were 1.49 (95% CI = 1.29-1.72), 1.51 (95% CI = 1.14e2.01), and 1.23 (95% CI = 0.39-3.86, P = 0.7197) for psoriasis patients receiving topical, systemic nonbiologic, and biologic therapy, respectively. Time to CD (but not UC) diagnosis was significantly longer for psoriasis patients compared with the general population, and patients receiving systemic treatment had the longest time to CD and UC. Psoriasis was associated with increased risk of CD and UC. Particular risk factors included sex and psoriatic arthritis.