Objective: To determine annual incidence and prevalence for patients consulting their GP because of Crohn's disease in England and Wales and compare demographic details with matched controls.
Design: We used the fourth Morbidity Statistics in General Practice study (MSGP-4) which covered 468 042 person-years during a 12-month period in 1991-92.
Methods: All GPs reporting a patient with Crohn's disease in MSGP-4 were sent a questionnaire to confirm the diagnosis and obtain supportive details (surgical, pathological, radiological and/or endoscopic). Data concerning ethnicity, social class, smoking status, living in an urban or rural environment and employment had been collected previously. Conditional logistic regression models were used to analyse the data for cases and matched controls.
Results: Three hundred and fifteen patients were reported to have Crohn's disease. Replies were obtained to 251 (80%) questionnaires. The diagnosis of Crohn's disease was confirmed in 184 cases (89%) and refuted in 23 cases (11%) -- details were unavailable for 44 patients. The mean age of patients was 44 years, the female:male ratio was 1.46:1, and 108 (59%) patients had required surgery. Thirty-three of 178 (18.5%) patients were diagnosed within the study period. Hence, this study detected a prevalence for consulting Crohn's disease of 54.6-59.8/100,000 and an annual incidence of 10.1-11.1/100,000 in 1991-92. No significant differences were found between cases (n = 291) and controls (n = 1682) with regard to ethnicity, social class, smoking or living in an urban/rural environment. Patients with Crohn's disease had similar employment levels as controls, but were significantly more likely to be registered as permanently sick, odds ratio 4.01 (CI 2.21-7.29).
Conclusions: This national survey, including 1% of the population, suggests there are approximately 30,600 patients consulting their GP because of Crohn's disease in England and Wales, with 5700 new cases diagnosed per year.