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The following extract is taken from the information booklet, "Living with Inflammatory Bowel Disease", published by the Canadian Journal of Gastroenterology.
There is some similarity in the epidemiology of ulcerative colitis and Crohn's disease. Both disorders are worldwide in the their distribution. The diseases occur most frequently in the developed countries of northern Europe and North America, with intermediate frequency in Central Europe, the Middle East and Australia, the least frequently in Asia and Africa. The annual incidence of IBD worldwide is from five to 15 new cases per 100,000 population in countries where it has been studied.
The ratio of ulcerative colitis to Crohn's disease varies from region to region but in most countries ulcerative colitis appears to occur more frequently than Crohn's disease. Since its first description in 1875, the incidence of ulcerative colitis has increased with each decade until the past three decades when it appears to have levelled off, with an annual incidence of four to 15 new cases per 100,000 population and a prevalence of 44 to 117 cases per 100,000 population.
It seems difficult to believe that clinicians of the early 20th century were unaware of the clinical manifestations and pathological findings of Crohn's disease. Since Crohn and his colleagues described the disease in 1932, the incidence of the disease has increased significantly greater than can be explained by better diagnostic facilities and by differentiation of the disorder from ulcerative colitis. The annual incidence of Crohn's disease varies from a low of 0.3 per 100,000 in Finland to a high of 13.5 in Minnesota. The prevalence varies from 28 to 108 cases per 100,000 population.
Epidemiological data on IBD in Canada is scanty. Mendelhoff quotes the incidence of of Crohn's disease in Sherbrooke, Quebec as 0.7 cases per 100,000 population and the prevalence as 6.3 cases per 100,000. These figures are low compared with published data for other countries. Recently, Pinchbeck et al. described the incidence of Crohn's disease and ulcerative colitis in Alberta as 10 and six cases per 100,000 population, respectively. The prevalence was 44 cases per 100,000 for Crohn's disease and 37.5 per 100,000 for ulcerative colitis.
Davis et al. estimated the incidence and prevalence of rates of IBD in southern Alberta. The incidence of ulcerative colitis in females was 1.8 per 100,000 and in males 2.4 per 100,000, while the incidence of Crohn's disease in females was 6.5 per 100,000 and in males 3.1 per 100,000. The prevalence rate for ulcerative colitis was 22.4 cases per 100,000 population in females and 24.7 per 100,000 in males. The prevalence rate for Crohn's disease was 63.7 per 100,000 for females and 38.1 for males. Depew et al., reporting on the clinical presentation of Crohn's disease in southern Ontario, described a prevalence of 33.1 cases per 100,000 population. More studies are obviously needed to document accurately the incidence of IBD in Canada.
The ratio of males to females is approximately equal, although women appear to have a 30% increased risk of developing IBD when population groups are predominantly English or northern European. The three most recent studies from Canada suggest that there is a slightly increased incidence in the female population.
The peak incidence of both diseases is between the ages of 15 and 25 years. Both diseases appear to be rare below the age of six and the incidence of ulcerative colitis appears to exceed that of Crohn's disease in the first decade. In some (but not all) series, there is an increase in incidence between ages 55 and 60 years.
IBD is more common in whites than in nonwhites. Both diseases are more common in Jews, particularly in studies from the United States and Scandinavia. Studies in Israel suggest that the incidence in Jews born in the western hemisphere is higher than in Jews born in Israel.
Approximately 18% of patients with IBD have family members with either ulcerative colitis or Crohn's disease, compared with 4% of controls. The tendency to have a relative with IBD is greater if the proband has Crohn's disease. This familial aggregation is probably genetic rather than the result of a common environmental factor; however, to date no genetic markers have been found to support a genetic basis for IBD.
1. Mendelhoff AI, Calkin BM. The epidemiology of inflammatory bowel disease. In: Kirsner JB, Shorter RG, eds. Inflammatory Bowel Disease, 3rd edn. Philadelphia: Lea and Febriger, 1988:3-34.
2. David FG, et al. Inflammatory bowel disease, incidence and prevalence in souther Alberta. Can J Gastroenterol 1990;4:187-92.
3. Depew WT, et al. Clinical presentation and course of Crohn's disease in southeastern Ontario. Can J Gastroenterol 1988;2:107-16.