Irritable bowel syndrome (IBS) is a common functional gastrointestinal (GI) disorder. Because not everyone needs to seek care, population-based studies are needed to truly understand the epidemiology of IBS. About 10% of the population has IBS at any one time and about 200 people per 100,000 will receive an initial diagnosis of IBS over the course of a year. IBS patients are more frequently younger in age, and a female predominance has been observed in Western countries and tertiary care settings. IBS patients commonly report overlapping upper GI, as well as a variety of non-GI, complaints.
Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder (FGID) that manifests as abdominal pain or discomfort and diarrhea or constipation, or both. The definition of IBS has evolved over time, from a diagnosis of exclusion to the symptom-based diagnostic criteria including Manning, Rome I, Rome II, and Rome III criteria. IBS is one of the most common disorders affecting the gastrointestinal (GI) tract. IBS accounts for 10% to 15% of primary care visits and 25% to 50% of gastroenterology referral visits. Data from the National Disease and Therapeutic Index (NDTI) showed that IBS accounts for 2.6 million office-based visits and 3.5 million all-location physician visits. However, a limited proportion of subjects suffering from IBS seek medical attention for this condition. Thus, knowledge of IBS epidemiology depends on research in the general population. This review addresses the comprehensive epidemiology in terms of prevalence, incidence, overlap, and natural history of one of the most common GI disorders, IBS.
Prevalence
For chronic conditions, the best way to estimate how commonly they occur is to report the number of people with the condition at any given time, the prevalence. In general, IBS is considered a highly prevalent FGID. However, IBS epidemiology varies considerably according to the definition used. Many population-based surveys have estimated the prevalence of IBS using the responses of surveys that record bowel symptoms. The prevalence rates in these studies have varied between 3 and 32 per hundred. Why do the prevalence rates from these IBS-specific symptom surveys vary tenfold? Although this may represent true differences in populations, it more likely reflects differences in the IBS definition. For example, the earlier Manning criteria are more generous and less restrictive than the recent Rome criteria. Higher prevalence rates are identified using a threshold of 2 of 6 Manning criteria. Lower prevalence rates are identified using more specific criteria, whether by increasing the threshold of Manning criteria necessary to make the diagnosis or using the Rome criteria. In a direct comparison, prevalence using standard Rome criteria is comparable to using a threshold of 3 of 6 Manning criteria. Moreover, Mearin and colleagues studied the differences between the Rome I and Rome II criteria, and found that only 31% of those meeting Rome I criteria met Rome II criteria for IBS. Those not meeting the Rome II definition met other FGIDs, such as functional constipation, functional diarrhea, or functional bloating. Recently, the symptom based diagnostic Rome III criteria for IBS has been developed and used, clinically and in research. The epidemiology of IBS may be difficult to interpret given these changing definitions.
The major IBS prevalence studies in Western countries are summarized in Table 1 . The range of prevalence is from 3% to 32%, with most studies reporting results between 5% and 15% depending on the definition applied. In a comprehensive review of the epidemiology of IBS in North America in 2002, the prevalence estimates for IBS in the United States ranged from 3% to 20%. In addition, this study showed that the prevalence decreased slightly with age, and the prevalence in women was slightly higher (2:1 female to male predominance). However, this study was performed before the development of the Rome II criteria. In more recent studies of the epidemiology of IBS in the United States or Canada using Rome II criteria, the prevalence of IBS has been estimated as from 5% to 12%. In another systemic review of IBS in 2007, which was based on 13 studies in European Union nations, the prevalence of IBS was approximately 4% based on Rome II criteria. In addition, there was a 2:1 female:male predominance.
| First Author, Ref. Country | Year | N | Case Definition | % IBS | ||
|---|---|---|---|---|---|---|
| Overall | Men | Women | ||||
| Talley, USA | 1987 | 835 | Manning 2 Manning 3 | 15.8 12.8 | 15.8 12.1 | 18.2 13.6 |
| Hahn, USA | 1989 | 42392 | Manning 2 Rome I | 3 12 | — | — |
| Drossman, USA | 1990 | 5430 | Rome I | 9.4 | 7.7 | 14.5 |
| Saito, USA | 1992 | 643 | Manning 3 Rome I | 15.7 8.4 | 13.5 8.4 | 17.7 8.4 |
| Mearin, Spain | 2001 | 2000 | Manning Rome I Rome II | 10.3 12.1 3.3 | 1.9 | 4.6 |
| Brommelaer, France | 2002 | 8221 | Manning Rome I Rome II | 2.5 2.1 1.1 | 1.7 1.4 0.9 | 3.1 2.8 1.3 |
| Thompson, Canada | 2002 | 1149 | Rome II | 12.1 | 8.7 | 15.2 |
| Boyce, Australia | 1997 | 2910 | Manning Rome I | 13.6 4.4 | 4.4 | 9.1 |
| Jones, England | 1992 | 1620 | Manning | 21.6 | 18.7 | 24.3 |
| Agreus, Sweden | 1988 | 1290 | Rome I | 12.5 | — | — |
| Wilson UK | 2003 | 4807 | Rome II | 8.1 | — | — |
| Hungin, Europe (UK, France, Germany, Italy, Holland, Belgium, Spain, Switzerland) | 2003 | 41984 | Overall Manning Rome I Rome II | 9.6 6.5 4.2 2.9 | 7.1 | 12 |
| Kennedy, UK | 1998 | 3179 | Manning 3 | 17.2 | 10.5 | 22.9 |
| Icks, Germany | 2002 | 1281 | Patient report | 12.5 | — | — |
| Kay, Denmark | 1994 | 4581 | Symptom criteria | 6.6 | 5.6 | 7.7 |
| Heaton, UK | 1992 | 1896 | Manning 3 Manning 2 | 9.5 21.6 | 5.0 18.7 | 13.0 24.3 |
| Hillila, Finland | 2004 | 3650 | Manning 2 Manning 3 Rome I Rome II | 16.2 9.7 5.5 5.1 | 13.1 8.3 5.1 5.1 | 19.2 11.2 6.1 5.3 |
| Jung, USA | 2004 | 2273 | Rome III | 11 | 8 | 14 |
| Olafsdottir, Iceland | 1996 2006 | 1336 799 | Manning 2 Rome III Manning 2 Rome II Rome III | 31 10 32 5.0 13 | — | — |
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