What is the peak age for onset of IBD?

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Although inflammatory bowel disease (IBD) now affects about 1 in 300 of the population in many Westernized countries and is a significant public health problem, its incidence (the number of new cases per year) is not high.¹ While there have been numerous studies of its overall incidence, many have involved identification of fewer than 200 new cases and have been too small to allow reliable assessment of age-specific incidence patterns. In addition, studies based on routinely collected data such as hospital admissions or primary care records have difficulty in distinguishing new (incident) cases from old (prevalent) cases suffering an IBD relapse.

Exceptionally large studies are required to determine incidence by age. There have been 4 such large studies recently in Europe and North America. The EC-IBD study² involved 2201 new IBD patients identified during 1990–1993 in 20 centers across Europe. Molinie et al³ reviewed all the IBD patients diagnosed by gastroenterologists within a region of northern France with a population of nearly 6 million. Over 7000 cases of IBD were recorded in the 10 years up to 1999 (4013 with Crohn's disease [CD] and 2,665 with ulcerative colitis [UC]). Bernstein et al⁴ identified 2380 cases of IBD in Manitoba, Canada, from a population of just over a million. They used an initial postal questionnaire and subsequent review of a proportion of the case notes. Moum et al⁵ reviewed the hospital records of all new diagnoses of IBD made between 1990 and 1993 in southeastern Norway. The baseline population was nearly a million and they identified 225 new cases of CD and 525 new cases of UC.