Has the rising incidence of Crohn's disease reached a plateau?

Has the rising incidence of Crohn's disease reached a plateau? Crohn's disease is a chronic condition of unknown cause and for which there is no effective medical treatment to prevent recurrence or spread. During 1934-77 the incidence of the disease in Cardiff greatly increased.' Since Cardiff has a stable, clearly defined population and a good medical records system it is particularly suited for an epidemiological study. We have therefore examined the incidence of Crohn's disease during 1976-80 and related the findings to an earlier report.' Patients, methods, and results Patients who were resident in the City of Cardiff when newly diagnosed with Crohn's disease were identified from a diagnostic computer index and from personal records belonging to clinicians, radiologists, and pathologists. Patients were considered to have Crohn's disease only if (a) the disease had been confirmed histologically in either the resected specimen or biopsy samples or (b) there was radiological evidence of Crohn's disease and a suitable clinical history. The patient's age, date, and distribution of disease at the time of diagnosis as well as the method by which the diagnosis had been first made were noted. Details of the population structure of Cardiff were obtained from census data and used to calculate incidence figures.