Clinical review
The epidemiology of irritable bowel syndrome in North America: a systematic review1

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Abstract

OBJECTIVE:

The aim of this study was to systematically review published literature about the prevalence, incidence, and natural history of irritable bowel syndrome (IBS) in North America.

METHODS:

A computer-assisted search of MEDLINE, EMBASE, and Current Contents/Science Edition databases was performed independently by two investigators. Study selection criteria included: 1) North American population-based sample of adults; 2) objective diagnostic criteria for IBS (i.e., Rome or Manning criteria); and 3) publication in full manuscript form in English. Eligible articles were reviewed in a duplicate and independent manner. Data extracted were converted into individual tables and presented in descriptive form.

RESULTS:

The prevalence of IBS in North America ranges from 3% to 20%, with most prevalence estimates ranging from 10% to 15%. The prevalences of diarrhea-predominant and constipation-predominant IBS are both approximately 5%. Published prevalence estimates by gender range from 2:1 female predominance to a ratio of 1:1. Constipation-predominant IBS is more common in female individuals. The prevalence of IBS varies minimally with age. No true population-based incidence studies or natural history studies were found. In one cohort surveyed on two occasions 1 yr apart, 9% of subjects who were free of IBS at baseline reported IBS at follow-up producing an onset rate of 67 per 1000 person-years. In all, 38% of patients meeting criteria for IBS did not meet IBS criteria at 1-yr follow-up.

CONCLUSION:

Approximately 30 million people in North America meet the diagnostic criteria for IBS. However, data about the natural history of IBS is quite sparse and renewed efforts should be focused at developing appropriately designed trials of the epidemiology of IBS.

Introduction

Irritable bowel syndrome (IBS) has been defined in the American Gastroenterological Association medical position statement as being “a combination of chronic or recurrent GI symptoms not explained by structural or biochemical abnormalities, which is attributed to the intestines and associated with symptoms of pain and disturbed defecation and/or symptoms of bloatedness and distention” (1). What makes IBS so challenging? The etiology is largely unknown, although different mechanisms for its symptoms have been proposed, including intestinal luminal irritants, psychological distress and psychiatric disease, postinfectious or postinflammatory phenomenon, and abnormal motor function 2, 3. More recently, abnormal visceral perception has been proposed as the mechanism behind the pain and abnormal defecation patterns (4). Because IBS lacks a “tangible lesion,” IBS has been classified as a functional disorder and, as such, has the potential to be trivialized.

However, the relevance of IBS in clinical practice cannot be questioned. IBS accounts for 25–50% of referrals to gastroenterologists (5). National health surveys estimate that each year, there are 3 million physician visits, 2.2 million prescriptions, as well as 96,000 hospital discharges for IBS (6). One study from Olmsted County, MN, measured health care use in a random sample of the population and found that the charges incurred by people with IBS symptoms were, on average, $300 higher than individuals without IBS (7). This figure, when extrapolated to the US population, would represent an excess of 8 billion dollars in medical costs among IBS patients. Therefore, knowledge of the epidemiology of IBS is clearly relevant to primary care providers, gastroenterologists, as well as policy makers.

Our purpose was to perform the first systematic review of published literature about the epidemiology of IBS in North America. Our specific study objectives were: 1) to determine the prevalence of IBS in North America, 2) to characterize the age of onset and gender distribution of IBS in North America, 3) to determine the incidence of IBS in North America, and 4) to characterize the natural history of IBS. Through this systematic review, limitations of current research may be identified and recommendations for future research may be suggested.

Section snippets

Search strategy for identification of studies

A computer-assisted search of three online bibliographic databases was conducted to identify potentially relevant published papers. A search of the MEDLINE database from 1966 to present was performed using medical subject heading (MeSH) term “colonic diseases, functional” [mortality, ethnology, epidemiology] or “colonic diseases, functional” with exploded keywords including “incidence,” “prevalence,” “prognosis,” and “natural history.” Review of the EMBASE database from 1991 to 2000 was

Characteristics of selected studies

Search of the MEDLINE database yielded 232 articles. Review of the EMBASE database yielded 191 articles. Searching the Current Contents database yielded 157 articles with the above-described search. Reviews of the titles and abstracts, followed by review of the full manuscripts of potentially relevant articles, identified eight articles that met inclusion criteria 12, 13, 14, 15, 16, 17, 18, 19. Only studies from the United States were found, as there were no published population-based studies

Discussion

Our systematic review of the literature has shown that the prevalence estimates for IBS in the United States have ranged from 3% to 20%; however, this wide range of prevalence estimates seems to be the result of changes in the definition of IBS used rather than true differences in IBS prevalence. No one definition can be considered a gold standard for the diagnosis, although the hope is that Rome II will become such. Unfortunately, the studies in this review were performed before the

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    The opinions and assertions contained herein are solely the views of the authors and should not be construed as official or as representing the views of the United States Government or the Department of Veteran Affairs.

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    Copyright © 2002 Am. Coll. of Gastroenterology. Published by Elsevier Inc. All rights reserved.