Abstract
INTRODUCTION: The ulcerative colitis (UC) to Crohn's disease (CD) incidence ratio varies across geography and time. METHODS: We analyzed UC:CD incidence ratios across three epidemiologic stages using generalized additive models for location, shape, and scale and pooled average annual percent changes (AAPCs) by meta-analysis. RESULTS: Ratios significantly decreased: median 3.62 in stage 1, 1.82 in stage 2, 1.55 in stage 3; the incidence ratio stabilized in stage 3 (AAPC: -0.12; 95%CI: -0.66, 0.42). DISCUSSION: Decreasing UC:CD incidence ratios signal a rising burden of CD, underscoring the need to anticipate greater healthcare demand, including higher treatment costs and higher prevalence of complications.