Causes Of IBD Explored Including 'Hygiene Hypothesis'

Main Category: Crohn's / IBD
Article Date: 08 Apr 2011 - 4:00 PDT


The American College of Gastroenterology published a new evidence-based systematic review on the management of Inflammatory Bowel Disease (IBD) as a supplement to The American Journal of Gastroenterology (AJG) for April 2011, a special issue entirely dedicated to IBD. This clinical monograph, based on a comprehensive meta-analysis, offers new graded recommendations on medical management of IBD, a chronic digestive disorder which includes Crohn's disease (CD) and ulcerative colitis (UC).

A section reviewing the epidemiology of IBD highlights several risk factors, including geography, smoking and appendectomy, the importance of the interplay between genes and environmental factors, including diets high in refined sugar, the role of the gut microbiome and the immune system, as well as the so-called "hygiene hypothesis" as a proposed explanation for the increased incidence of IBD in industrialized nations.

The ACG Institute for Clinical Research & Education convened an expert Task Force to undertake a systematic review of trials evaluating medical therapies of active and quiescent CD and UC. Therapeutic approaches to inducing and maintaining remission, as well as preventing relapse, were included in the analysis. The evidence for the following therapies was included in the systematic review: 5-ASAs, corticosteroids, antibiotics, biologics and immunosuppressants.

"A series of systematic reviews performed by methodologists and supported by IBD experts provides an authoritative perspective on the efficacy of medical therapies in IBD," explained Paul Moayyedi, B.Sc., M.B. Ch.B., Ph.D., MPH, FRCP, FRCPC, FACG, who, along with colleagues at McMaster University and University of Leeds conducted the comprehensive meta-analysis. Dr. Moayyedi also serves as Co-Editor of AJG. "The assessment of all the trials in both UC and CD using the same criteria by one group of researchers gives a unique overview of the strength and quality of the evidence."

"While many review articles, including systematic reviews, have been published on therapy for IBD, the ACG Task Force represents the most rigorous attempt to date to synthesize all of the available evidence in an unbiased fashion. I believe it will prove an invaluable guide for clinicians and investigators," commented Nicholas J. Talley, M.D., Ph.D., FACG, who chaired the ACG IBD Task Force.

"ACG's goal was to highlight the wealth of randomized controlled trial data that can guide the clinician in the medical management of IBD," explained Delbert L. Chumley, M.D, FACG, President of the American College of Gastroenterology.

Summary of Epidemiological Evidence Offers Fascinating Hypotheses for IBD's Causes

An estimated 1.5 million Americans suffer from UC and CD. Geography is a factor in the incidence of CD. There is a North-South gradient with a strong correlation between degrees latitude and CD incidence when the Western Hemisphere and Western Europe are evaluated. This North-South gradient also exists in the United States, with CD being less common in the South. While a similar epidemiological pattern exists for UC, the North-South gradient is not as pronounced according to the findings presented.

Those with certain immune function predispositions are more like to develop IBD, and the most likely candidate may reside within the gut microbiome, with changes in the gut flora associated with increased risk of IBD in two studies. Dietary factors are also associated with the emergence of IBD, particularly in countries where industrialization has lead to a change in eating patterns and types of foods consumed. One culprit consistently associated with CD is a diet high in refined sugar. Finally, the association with the increased risk of IBD among those living in a cleaner environment, known as the "hygiene hypothesis," points to need to investigate both the immune system and the gut flora as way to enlarge understanding of the causes of IBD, according to the monograph authors.

About IBD

Inflammatory Bowel Disease (IBD) is one of the most common disorders managed by gastroenterologists. Ulcerative colitis and Crohn's disease are two types of IBD. The large intestine (colon) is inflamed in ulcerative colitis, and this involves the inner lining of the colon. In Crohn's disease the inflammation extends deeper into the intestinal wall. Crohn's disease can also involve the small intestine (ileitis), or can involve both the small and large intestine (ileocolitis). IBD develops due to inflammation in the intestine which can result in bleeding, fever, elevation of the white blood cell count, as well as diarrhea and cramping abdominal pain. The abnormalities in IBD can usually be visualized by colonoscopy or cross-sectional imaging (e.g., CT scan.)

Recent advances in basic science research which have revealed new insights into the role of specific immune cells and their mediators in intestinal inflammations. Both UC and CD exhibit a relapsing and remitting course and there is a significant, often dramatic, reduction in patients' quality of life during exacerbations of the disease which has an impact on psychological health.

Source:
Jacqueline Gaulin
American College of Gastroenterology

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