Every 29th May, WGO celebrates World Digestive Health Day (WDHD) and initiates a worldwide public health campaign through its 110 national societies and 50,000 members. Each year focuses upon a particular digestive disorder to increase general public awareness of prevention and therapy. Prior campaigns emphasized different topics: Health and Nutrition (2005), Helicobacterpylori Infection (2006), Viral Hepatitis (2007), Optimal Nutrition in Health and Disease (2008), and Irritable Bowel Syndrome (2009), and over this time the WDHD campaign has been transformed into an all year long awareness endeavor which in 2010 highlights Inflammatory Bowel Disease (IBD).
HAS THE EPIDEMIOLOGY OF IBD CHANGED, ESPECIALLY DURING THE PAST 10–20 YEARS—AND IF SO, ARE THERE DIFFERENCES IN THESE CHANGES BETWEEN ULCERATIVE COLITIS AND CROHN'S DISEASE?
CB: IBD emerged in the early to mid-20th century in the developed world. When it emerged, there was a predominance of ulcerative colitis (UC) over Crohn's disease (CD), and CD was 1.3 times more common in women. In the last decade in the developed world, CD has become the predominating disease, with incidence rates higher than those for UC in most countries. There has also been more of a balance between women and men. In fact, several studies on children have shown that there now is a greater incidence among boys than girls. Meanwhile, over the past 10 to 15 years, IBD has emerged to a greater extent in the developing world and even in developed countries where it was previously uncommon, such as Japan. However, UC is predominant in these emerging nations, much as it was in the West several decades ago.
It is not known why UC presents first and is then overtaken by CD in areas in which IBD emerges. The province of Manitoba in Canada is interesting. Like other Canadian provinces, Manitoba has among the highest incidence rates of CD in the world, at approximately 15 per 100,000. However, 10% of Manitoba's population are First Nations, or North American Indians. This community has very low rates of IBD, but UC predominates over CD by a factor of 4 within their IBD population. Members of this ethnic community often live in crowded housing and in areas with a high prevalence of infections that are transmitted by the fecal–oral route, such as hepatitis A and Helicobacter pylori. These communities living in Canada share the same epidemiological profile for IBD that developing nations have.
WHAT CAN BE HYPOTHESIZED ABOUT THE ETIOLOGY OF THE DISEASES FROM WHAT IS KNOWN ABOUT THE EPIDEMIOLOGY OF IBD?
CB: When exploring the etiology of IBD, it can be as revealing to study communities that do not get the disease as it is to study those that do (such as the indigenous population in Manitoba juxtaposed to the White population). However, as the disease emerges in the developing world, it will be of great interest to explore environmental changes in those countries, as this may make it possible to define what may be spurring this emergence of IBD. One hypothesis that has evolved in relation to many chronic immune diseases is the “hygiene hypothesis.” This hypothesis posits that in communities where there is a reduction of communicable infectious diseases (some of which may even be fatal), there is a parallel rise in chronic immune diseases. If the developing immune system is not exposed to microorganisms in childhood, it may not become tolerant of microorganisms with similar antigenicity later in life. Another angle to the hygiene hypothesis is the possibility that it is not a lack of pathogenic organisms in youth, but rather a reduction in saprophytic, potentially probiotic-type organisms that are able to downregulate injurious immune responses by triggering regulatory T cells. What could alter this microbial ecology? Is it the increasing use of antibiotics? Is it a change in diet? Is it a change away from an agricultural milieu to a more industrial one? These are the types of issue that require investigation.
ARE THERE DIFFERENCES IN THE PRESENTATION OF CD IN DIFFERENT AREAS OF THE WORLD?
CB: This is the type of issue that really requires further exploration. In the recent Practice Guidelines prepared by a number of gastroenterologists from around the world under the auspices of the WGO, we created a cascades approach to diagnosing and managing IBD in different regions of the world (Inflamm Bowel Dis. 2010;16:112–24). CD is distinguished from UC by disease proximal to the colon, perineal disease, fistulas, histologic granulomas, and full thickness as opposed to mucosa limited disease. In CD, granulomas are evident in up to 50% of patients and fistulas in 25%. It is noteworthy that the presentation of CD and UC is quite similar in such disparate areas of the world as North America, South America, Europe, Australia, and New Zealand.
But there are also differences. In Pakistan, for example, there is much less extraintestinal disease with both UC and CD than is reported in the West (where up to 25% of patients have extraintestinal manifestations, if arthralgias are included). In Pakistan, few patients have perianal or fistulizing disease. In India, for example, the age of presentation of CD is a decade later than in the West, colonic involvement is more common, and fistulization seems less common. More information is needed to discern whether there are differences in the IBD phenotype in some of the nations where it is now newly emerging.
IF THE INCIDENCE RATES OF IBD ARE LOWER IN THE DEVELOPING WORLD THAN IN THE DEVELOPED WORLD, WHAT HAPPENS TO THE INCIDENCE RATES AMONGST IMMIGRANTS TO THE DEVELOPED WORLD? IS THERE A DIFFERENCE BETWEEN UC AND CD?
CB: It seems that immigrants retain the incidence rates of their birth countries for diseases like IBD, so that immigrants from the developing world to the developed world have low rates of IBD. However, there are suggestions from Britain and Vancouver that the offspring of immigrants who are raised in the West have incidence rates that are comparable to the White populations of those countries. This has been published for UC, and it may be similar in CD. This type of finding supports the notion that the environment has a stronger impact on the development of the diseases than genetics.
SHOULD THE APPROACH TO TREATING IBD BE SIMILAR AROUND THE WORLD?
CB: The approach to treating IBD around the world will have to be tailored to the availability of treatments in the various countries. It would be optimal if the best approach was available universally, but it is less likely that the expensive therapies used in the West will become as widely available in developing nations. Furthermore, there may be issues of access to health care in developing nations that are not as problematic in the West. This is reviewed in the WGO Practice Guidelines.
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