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.

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.