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 | — | — |
Table 2 summarizes the major epidemiologic studies in Asian countries. The prevalence of IBS by the Rome II criteria in Asia has been reported to range from 1% to 22%. Across Asia, the prevalence of IBS is higher in the younger age groups. Of note, the female predominance reported in the West has not been reported in some Asian countries. It is noteworthy that a higher prevalence of IBS in males has been reported in some Asian countries.
| First Author, Ref. Country | Year | N | Case Definition | % IBS | ||
|---|---|---|---|---|---|---|
| Overall | Men | Women | ||||
| Gwee, Singapore | 1998 | 2276 | Manning 2 Rome I Rome II | 11 10.4 8.6 | 9.5 9.0 7.8 | 12.6 11.7 9.4 |
| Xiong, South China | 2002 | 4178 | Manning Rome II | 11.5 5.7 | 9.7 5.0 | 13.0 6.3 |
| Lau, Hong Kong | 1996 | 1298 | Rome II | 3.7 | 3.6 | 3.8 |
| Ho, Singapore | 1990 | 696 | Manning | 2.3 | — | — |
| Kwan, Hong Kong | 2000 | 1797 | Rome II | 6.6 | — | — |
| Danivat, Thailand | 1988 | 1077 | Manning | 4.4 | — | — |
| Masud, Bangladesh | 2000 | 2426 | Rome I | 8.5 | 5.8 | 10.7 |
| Rajendra, Malaysia | 2000 | 949 | Rome II | 14 | — | — |
| Ghoshal, India | 2005 | 7285 | Clinical | 4.2 | 4.3 | 4.0 |
| Han, Korea | 2004 | 1066 | Rome II | 6.6 | 7.1 | 6.0 |
| Husain, Pakistan | 2006 | 880 | Rome II | 13.3 | 13.1 | 13.4 |
| Lu, Taiwan | 2001 | 2865 | Rome II | 22.1 | 21.8 | 22.8 |
| Miwa, Japan | 2006 | 10000 | Rome III | 13.1 | 10.7 | 15.5 |
| Sorouri, Iran | 2006 | 18180 | Rome III | 1.1 | 0.6 | 1.5 |
Based on Rome III criteria, the prevalence of IBS has been estimated to range from 10% to 18% in the general population of Western countries, whereas the prevalence of IBS reported from Asian countries has been from 1% to 9%. The prevalence of IBS does decrease slightly with age, although new-onset symptoms may occur in the elderly. Also among the elderly, Talley and colleagues showed that the prevalence of IBS was found to increase with age from 8% among those aged 65 to 74 years to more than 12% for those older than 85. However, more and better data are needed.
Overall, the prevalence of IBS has been reported as between 2% and 15% from Western or Asian countries, with IBS patients more frequently younger in age. Female predominance is more prevalent in Western countries or tertiary hospital care settings. Of course, comparison across countries is made difficult because of language and cultural differences. Even in the same study, questionnaires need to be developed and validated for each language, and even then one’s threshold to endorse symptoms may vary.
Regarding IBS bowel habit subtypes, one systemic review reported that population-based studies from the United States (Manning) found similar distributions among constipation predominant IBS (IBS-C), diarrhea predominant IBS (IBS-D), and IBS alternating between diarrhea and constipation (IBS-A), while European studies (Rome I, Rome II, or self-reporting) showed either IBS-C or IBS-A as the most prevalent subtypes. For example, in one study approximately 16% of the IBS patients had IBS-C, 21% had IBS-D, and 63% had IBS-A. Whether the agreement between subtyping of IBS patients based on Rome II versus Rome III criteria is good or poor is controversial. Very few data by IBS subgroup based on the recent Rome III classification system are available.
Incidence
Incidence of IBS is not easy to estimate, because IBS may develop slowly and people may not seek care. From a population-based study in the United States, which was based on 2 surveys sent to a random sample of population about 1 year apart, the IBS onset rate was 9%. However, in another study based on physician-based IBS diagnosis in the same population, the incidence rate of clinically diagnosed IBS was much lower, 196 cases per 100,000 person-years. A study from Europe showed a similar annual incidence rate of IBS, about 200 to 300 per 100,000 people. Symptoms may come and go and change over time. Thus, the coming and going of IBS may not represent a brand new case. Therefore, the 9% onset rate may have occurred in people who had IBS at some time in the past. Similarly, many people with IBS in the community do not seek care. The incidence of a clinical diagnosis of IBS is likely an underestimate. Nonetheless, if only half seek care, the observed incidence can be doubled to 400 per 100,000 per year and then multiplied by a 20-year disease duration to get a prevalence of 12%, which is in keeping with the data. Moreover, IBS may develop in a higher proportion of patients with certain conditions, such as an acute episode of infectious gastroenteritis. From a systematic review of postinfectious IBS, the incidence rate of IBS in patients with acute GI infection has been reported to be 10% (95% confidence interval: 9.4–85.6).
Overlap with Other Functional Gastrointestinal Disorders
Patients with IBS seeking health care commonly report other GI and/or extraintestinal complaints. Because of how commonly it occurs, it is possible that IBS overlaps with other intestinal or extraintestinal diseases simply due to chance. However, many population-based and clinical studies have reported the associations with other diseases, specifically other FGIDs. For example, a community study in the United Kingdom showed that IBS, gastroesophageal reflux disease (GERD), and symptomatic bronchial hyperresponsiveness occurred more frequently together than expected; in subjects with IBS, 47% had GERD. Also, in a United States community study, Jung and colleagues showed that IBS and GERD occurred together more commonly than expected by chance; the prevalence of IBS-GERD overlap was 4% of the population. Finally, a recent systematic review of the overlap of GERD and IBS using the population-based studies and clinical studies suggested that there is a strong overlap between GERD and IBS that exceeds the individual presence of each condition. A recent systematic review evaluated the relationship between dyspepsia and IBS using 19 eligible studies (13 population-based and 6 clinical studies). The analysis showed that the degree of overlap between the two conditions varied from 15% to 42%, depending on diagnostic criteria used for each, and individuals with dyspepsia had an eightfold increase in prevalence of IBS compared with the population. Thus, the demonstration of significant overlap with other FGIDs raises the question as to whether these disorders should be considered a more common clinic entity or not. Locke and colleagues showed in a community based study that 4% to 9% of the population had any 2 GI symptom complexes and 1% to 4% of the population had 3 GI symptom complexes. Many other studies also have shown overlap of pairs of FGIDs. Although many possibilities exist, the mechanism behind this overlap is not yet clear.
Overlap with Extraintestinal Disorders
At least one subset of IBS patients also suffer with non-GI symptoms. IBS patients make 2 or 3 times as many non-GI health care visits as control subjects. Non-GI nonpsychiatric disorders documented to be associated with IBS in a detailed literature review included chronic fatigue syndrome (51%), chronic pelvic pain (50%), and temporomandibular joint disorders (64%). In referred patients with IBS, psychiatric disorders have also been reported to be very common, leading some to argue that IBS is a part of the psychiatric disease spectrum and not a unique condition. Whitehead and colleagues performed a study comparing the comorbidities between 3153 patients with IBS and age- and gender-matched controls in a health maintenance organization. They found that psychiatric disorders, especially major depression, anxiety, and somatoform disorders, occur in up to 94% in IBS patients. The investigators argued that the elevated incidence of non-GI disorders might occur in a subset because patients with IBS are hypervigilant and consult much more readily for problems than those without IBS, although this remains to be established. Some of the burden of extraintestinal comorbid conditions may also be explained by somatization or other psychiatric disorders coexisting with IBS, but this could not account for at least two-thirds of patients with IBS. In fact, there has been a recent movement to overhaul the classification of somatoform disorder. Thus, in the future much can be learned about the prevalence and epidemiology of IBS with regard to overlap or comorbid conditions, which may help lead to a more appropriate classification scheme and management.
Related posts:
The Role of Diagnostic Testing in Irritable Bowel Syndrome
Centrally Acting Therapies for Irritable Bowel Syndrome
Emerging Pharmacological Therapies for the Irritable Bowel Syndrome
Inflammation and Microflora
The Role of Diagnostic Testing in Irritable Bowel Syndrome
Emerging Pharmacological Therapies for the Irritable Bowel Syndrome
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
