Time trends in patients with ulcerative colitis and crohn’s disease not receiving IBD-specific pharmacological treatment within one and three years of diagnosis – a nationwide cohort study

Abstract

BACKGROUND AND AIMS: Most patients with Crohn's disease (CD) or ulcerative colitis (UC) receive medication at diagnosis, but some do not. We examined 25-year trends in the proportion of newly diagnosed IBD patients not receiving any pharmacologic treatment within one or three years of diagnosis. METHODS: Using national health registries, we identified all incident CD and UC patients in Denmark from 1996-2020. IBD-specific medication use was captured from one month before diagnosis through one and three years after diagnosis. Patients with no recorded IBD-specific pharmacological treatment were classified as pharmacologically untreated. Proportions were assessed by age at diagnosis (<18, 18-59, ≥60 years) and calendar period. RESULTS: Among 51,045 incident IBD patients, 21% of those with CD and 12% with UC received no IBD-specific pharmacological treatment within one year of diagnosis. At three years, the corresponding proportions were 16% and 9%. Across calendar periods, the proportion pharmacologically untreated within one year increased from 19% (95% CI 17-21) to 24% (95% CI 22-25) in CD and decreased from 14% (95% CI 12-15) to 10% (95% CI 9-10) in UC. Older patients had the highest proportions. CONCLUSIONS: Approximately one in five patients with CD and one in ten patients with UC received no IBD-specific pharmacological treatment in the first year after diagnosis. Over 25 years, this proportion decreased in UC but remained high in CD, especially in older adults. These findings highlight a substantial pharmacologicallyuntreated subgroup and warrant further investigation of the underlying clinical pathways and long-term outcomes.