ABSTRACT Introduction Epidemiological measures of inflammatory bowel disease (IBD) evaluate the current and future burden of IBD on the health system. Long‐run incidence studies can identify changes in disease patterns and potentially give clues about aetiology if environmental risk factors have also changed. Methods Clinic records and databases were retrospectively searched for adults and children diagnosed with IBD in the Otago region, southern New Zealand to the end of 2024. Medical chart review confirmed cases using standard IBD diagnostic criteria, and the Montreal phenotype, diagnostic delay, medical and surgical treatments were extracted. Previous data from Otago were included to compare incidence over time. Results Between 2014 and 2024, there were 438 patients diagnosed with IBD in Otago, giving an average annual incidence rate of 19.7 per 100,000 (95% CI 17.9–21.6). The rates of Crohn's disease (CD) and ulcerative colitis (UC) were 8.5 (95% CI 7.4–9.8) and 10.6 (9.3–12.0) per 100,000, respectively. Most (87%) patients were of NZ European ethnicity. Individuals with CD had a lower median age (years) at diagnosis: 25.5, compared to those with UC: 40, ( p < 0.001). The median diagnostic delay was 6 months (IQR 3–9). Comparing the most recent decade (2014–2024) with previous data (1996–2013), the incidence of IBD rose from 14.2 to 19.7 per 100,000, ( p < 0.001). Over that period, the CD increase did not reach statistical significance, whereas the UC increase did. Conclusion This long‐run incidence study observed the incidence of IBD in Otago continues to increase, representing a growing burden to patients and the health system.
Cochrane et al. (Thu,) studied this question.
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