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P662 Evolution of IBD incidence, disease phenotype, and mortality; 20 years of epidemiologic research in the Dutch population-based inflammatory bowel disease South Limburg cohort

T. van den Heuvel*1, 2, S. Jeuring1, 2, M. Zeegers3, 4, D. van Dongen1, A. Wolters1, A. Masclee1, 2, M. Romberg-Camps5, L. Oostenbrug5, M. Pierik1, 2, D. Jonkers1, 2

1Maastricht University Medical Centre+, Division of Gastroenterology and Hepatology, Maastricht, Netherlands, 2Maastricht University Medical Centre+, Nutrim - School of Nutrition and Translational Research in Metabolism, Maastricht, Netherlands, 3Maastricht University Medical Centre+, Department of Complex Genetics, Maastricht, Netherlands, 4Maastricht University Medical Centre+, Caphri - School of Public Health and Primary Care, Maastricht, Netherlands, 5Zuyderland Medical Centre, Department of Internal Medicine, Sittard-Geleen-Heerlen, Netherlands

Background

To reliably establish time trends in inflammatory bowel disease (IBD) epidemiology, long-term, stable, population-based cohorts are warranted. We studied time trends in incidence, disease phenotype at diagnosis, and mortality between 1991 and 2010 in adult IBD patients from South Limburg (population-based IBDSL cohort, NL).

Methods

The IBDSL cohort used a multifaceted approach (hospital databases, Dutch pathology database, and GPs) to identify incident IBD patients, and reached over 93% completeness. In total, 1 162 patients with Crohn’s disease (CD), 1 663 with ulcerative colitis (UC), and 84 with unclassified IBD were diagnosed between 1991 and 2010 and followed until 2013. Complete clinical data were collected using medical records. Time trends in incidence were studied using jointpoint regression analysis, in disease phenotype at diagnosis (Montreal classification) using linear and multinomial regression analysis, and in mortality using standardised mortality rates (SMR). In addition, IBD prevalence (2010) was estimated using historic hospital databases, and migration- and life-expectancy tables. Analyses were done for IBD, as well as for CD and UC, separately.

Results

IBD incidence increased from 17.5/100 000 in 1991 to 39.0/100 000 in 2010, with an average annual percentage change (AAPC) of 4.1%. The incidence was stable until 1999, followed by an increase thereafter (p = 0.01). An increasing incidence was also observed for CD (5.8/100 000 to 17.5/100 000; AAPC 6.0%; p < 0.01) and UC (11.7/100 000 to 21.5/100 000; AAPC 3.8%; p < 0.01) (Figure 1). Mean age at CD diagnosis increased from 35.0 years (SD 14.8) to 36.9 (SD 15.5; p < 0.01), and at UC diagnosis from 42.5 (SD 17.0) to 45.9 (SD 16.6; p < 0.01). Distribution of IBD location at diagnosis changed over time, represented by a decrease in ileal CD (AAPC -1.9%; p = 0.03) and an increase in UC patients with proctitis (AAPC 1.9%; p = 0.03). IBD mortality was similar compared with the general population (SMR 0.92; 95%CI 0.81–1.05), as were CD and UC mortality, and no change was observed over time. In 2010, the prevalence estimate was 830/100 000 for IBD, 327/100 000 for CD and 468/100 000 for UC.

Figure 1. Incidence and phenotype characteristics at diagnosis in Crohn’s disease and ulcerative colitis.

Conclusion

In South Limburg, the incidence of IBD, CD, and UC is high compared with international data, and doubled between 1991 and 2010. Together with a normal mortality risk, this led to high prevalence. The sudden increase in IBD incidence and the shift in phenotype at diagnosis are the starting point for a risk-factor analysis, including ecologic data from Geographic Information Systems.