Infectious Diseases
Crohn’s Disease
Inflammatory bowel disease (IBD) is a term used to describe two distinct disease states, Crohn’s disease and ulcerative colitis, which cause inflammation of the intestine.
Crohn’s disease is a serious inflammatory disease of the gastrointestinal (GI) tract. Unlike ulcerative colitis, which affects only the innermost lining (mucosa) of the large intestine, Crohn’s disease involves inflammation of the full thickness of the intestinal wall and predominates in the lower part of the small intestine (ileum) and the large intestine, but may occur in any section of the GI tract from the mouth to the anus. Depending on where in the GI tract inflammation occurs, Crohn’s disease may be referred to as ileitis (small intestine), regional enteritis, or colitis (large intestine).
Although Crohn’s can occur at any age, the majority of patients are identified between the ages of 15 and 30 years.
The diagnosis of Crohn’s disease (as for ulcerative colitis) may be delayed as many of its symptoms mimic those of other diseases. It is usually necessary to exclude diseases such as bowel infections or the irritable bowel syndrome before a definitive diagnosis can be reached.
Despite a great deal of research, the cause(s) of Crohn’s disease remains unknown. Proposed mechanisms and causative agents for Crohn’s disease have ranged from the involvement of cereals, toothpaste or a more general food allergy to viruses and autoimmunity. Some researchers believe that evidence is accumulating to demonstrate the involvement of an environmental Mycobacteria strain, Mycobacterium paratuberculosis, in a substantial majority of Crohn’s disease patients.
Prevalence & Incidence
Crohn’s disease is a condition that shows significant geographic and racial variability with regard to its incidence and prevalence. IBD has become more frequent during the past decades, with an approximate prevalence of 0.5% in the northern hemisphere.
In the USA Crohn’s disease affects approximately one million people and there are an estimated three to twenty new cases of IBD recognized per 100,000 persons per year3. In Canada the overall incidence rates of Crohn’s disease and ulcerative colitis were identical at 15.6 per 100,000 people. Both diseases showed substantial geographic variation, with the incidence of IBD being higher in urban areas.
In England the incidence of Crohn’s disease is estimated at 8.3 per 100 000 per year. Prevalence rates, but not incidence rates, for IBD have recently been found to be substantially higher than previously described in UK populations. In Wales, eighty-four new patients with Crohn’s disease, and resident in Cardiff, were diagnosed between 1991 and 1995. The mean incidence of the disease was determined to be 5.6 cases per 100,000 per year.
In Spain Crohn’s disease incidence figures range from 0.4 to 5.5 cases per 100,000 per year, with an average rate of 1.9. The incidence of IBD appeared to be relatively different depending on the geographical region of the country studied. There has been an increase in Crohn’s disease over time in Spain and it is no longer considered a rare disease, but a relatively frequent one.
The prevalence of Crohn’s disease for migrant South Asians in Europe is decreased compared with Europeans. However there are no obvious differences in age or sex distribution or rates of familial aggregation, and there are no significant differences in the clinical characteristics and natural history of Crohn’s disease in Asians compared with other racial groups with IBD
In Japan the number of patients with Crohn’s disease has increased remarkably since the 1980s. The prevalence and the annual incidence of patients with Crohn’s disease in Japan were estimated to be approximately 2.9 and 0.6 per 100 000 population in 1986, respectively, compared to 13.5 and 1.2 per 100 000 population in 1998. The overall prevalence of Crohn’s disease in Singapore was found to be 3.6 per 100,000 In a study of 58 IBD patients in Singapore, of the 21 patients with Crohn’s disease 81% were Chinese, 9.5% Malay and 9.5% Indian. This is broadly in line with the ethnic distribution of the population.
It is estimated that more than 23,000 Australians have IBD. Of these approximately 10,000 have Crohn’s disease and 13,000 have ulcerative colitis. From the above it is evident that Crohn’s disease is a condition that demonstrates significant geographic variability and is growing in clinical importance in many parts of the world.
Economic Cost
A team of researchers in the US analysed the cost of Crohn’s disease dependent on the severity of symptoms in 2000 and published their findings in The American Journal of Gastroenterology . Six hundred and seven Crohn’s sufferers were stratified into three mutually exclusive disease severity groups: those requiring hospitalization, patients requiring chronic glucocorticoid or immunosuppressive drug therapy for >6 months and all remaining patients. The authors found that the average annual cost per patient for all patients totalled US$12,417. Those requiring hospitalisation experienced the highest mean charges (US$37,135), whereas patients in groups 2 and 3 incurred US$10,033 and US$6,277.
In contrast a previous study using a literature-based medical decision algorithm costing methodology estimated that the average annual treatment cost per Crohn’s patient was US$6,561 in 1990. Using their algorithm the authors estimated the total annual medical costs for U.S. Crohn’s disease patients in 1990 was US$1.0-1.2 billion. The US National Institute of Diabetes, Digestive and Kidney Diseases cites the number of annual hospitalizations related to Crohn’s disease at over 64,000 with an average cost of treatment for complications of $37,135 per hospitalization.