Irritable Bowel Syndrome in Iran: SEPAHAN Systematic Review No. 1.

OBJECTIVES: Irritable bowel syndrome (IBS) is a common gastrointestinal disorder. Due to its high prevalence and absence of curative therapy, IBS has the potential to create tremendous burden on the health care system. Herein, we systematically reviewed the published literature to investigate the epidemiology of IBS in Iran.
METHODS: Studies that were reviewed in this article were primarily identified through four online bibliographic databases including PubMed, Google Scholar, Iran Medex, and Scientific Information Database. Manual search of reference lists was carried out to identify any additional studies such as relevant abstracts and also recent review articles which may have been missed. Potentially related studies were retrieved and the selection criteria were applied. Eligible articles were reviewed.
RESULTS: From 4176 studies identified, 18 eligible studies were included. It was reported that in Iran, the prevalence of IBS was in the range of 1.1% to 25% and was more common in women. In addition, the difference in frequency of different age groups was minimal. There was a minimal difference in IBS prevalence within different age groups.
CONCLUSIONS: In Iran, the incidence of IBS was in the wide range. Since there are not enough population-based studies, researchers should focus on developing well-designed population-based studies to determine the epidemiology of IBS in Iran. Moreover, cohort studies should be conducted in order to investigate the natural history of IBS. Investigating the etiology of IBS and attempt to organize health promotion programs are highly suggested.

INTRODUCTION

Irritable bowel syndrome (IBS), as the most common functional gastrointestinal disorder (FGID), is characterized by abdominal pain or discomfort and alteration of bowel habits and disordered defecation, in the absence of organic disease.[1]

Despite the high prevalence of IBS in general population and the personal and economic costs, its etiology remains vastly unknown; however, various studies have shown that several factors including abnormal motility of intestine, visceral hypersensitivity, inflammation, neurotransmitter imbalance, disturbance of brain-gut interaction, abnormal central processing, autonomic and hormonal events, and genetic, environmental, and psychosocial factors may contribute in incidence of IBS.[2]

It is believed that the incidence of IBS is more prevalent in women than in men and the age of its onset is in the range of 30 to 50 years.[3] The prevalence of IBS varies across the world, ranging from as high as 9% to 22% in the United States and European countries, to as low as 4.2% and 4.4% in India and Thailand, respectively, based on various diagnostic criteria.[3-5]

It was reported that prevalence of IBS was 3 to 20 % in the North America.[6] The prevalence of IBS in 8 European countries was 11.5%.[8] In Singapore the prevalence of IBS was estimated to be 11, 10.4 and 8.6%, respectively, by using Manning, Rome I, and Rome II criteria.[8] Such variation in these reports may be due to the difference in selected population in each study or even using different criteria in diagnosing IBS. Recently, it has been observed that the prevalence of IBS is raising among Asian communities.[89]

Several studies in Iran have also reported the prevalence of IBS in different populations. Mahmoudi et al. determined it to be 4.2% based on Rome I criteria.[10] While Pourshams et al. by employing Rome II criteria, reported that the prevalence of IBS in students of Tehran University was 4.75%.[11] The prevalence of IBS in Iranian blood donors was 5.6%.[12] The prevalence of IBS in 18180 people in five cities in Tehran province was estimated to be about 1 % by employing III criteria;[13] whereas Ganji et al. by using Rome II diagnostic criteria, demonstrated that the prevalence of IBS in the city of Tehran was about 25% and also claimed that IBS was the second most prevalent gastrointestinal disorder after gastroesophageal reflux disease in outpatients visiting gastrointestinal clinics.[14]

IBS has strong negative effect on quality of life in patients who suffer from it and it imposes substantial social and economic costs due to medical seeking behavior and absenteeism.[15-20] In the United States, the direct and indirect cost of IBS has been estimated to be between 1.7 to 10 million dollars and 19.2 million dollars per year, respectively.[2122] One study in Iran investigated the economic burden of IBS, and showed that the cost of IBS in Iran is about 2.8 million dollars and this is of great significance for Iranian population.[23]

To our knowledge, there has not been any review article in relation to the prevalence of IBS in Iran until now. The aim of this study was to systematically review the articles about the epidemiology of IBS in Iran, to discuss the limitations of current research on this subject and to make recommendations for future studies. In addition, this review provides background knowledge for the “Study on the Epidemiology of Psychological, Alimentary Health and Nutrition” (SEPAHAN).[24] The data of SEPAHAN will explore the epidemiology of FGIDs in Isfahan province and it will be published later by the same study group.

METHODS

This is a systematic review of all published studies on the epidemiology of IBS in Iran.

Literature Search

. Studies that were used in the present review were primarily identified via searching in four online bibliographic databases including PubMed, Google Scholar, Scientific Information Database and IranMedex. Our PubMed search query was as follows: (IBS[All Fields] OR (“irritable bowel syndrome”[MeSH Terms] OR “irritable bowel syndrome”[All Fields])) AND “Iran”[All Fields]). Review of the Google Scholar database was done using the following terms: “Irritable bowel syndrome”, “IBS”, and “Iran”. Likewise, we used keywords like “irritable bowel syndrome” and “IBS” for searching relevant articles in the Persian bibliographic databases (www.sid.ir) and IranMedex (www.iranmedex.ir). In addition, manual search of reference lists from studies with relevant abstracts and recent reviews was carried out. Search of all databases from inception to present was done and the last search was conducted on March 10, 2012.

. Two investigators reviewed the titles and abstracts of all citations for eligibility criteria, to include the studies in the review. Potentially relevant studies were retrieved and selection criteria were applied. Selected articles were studies that 1) had adult sample populations; 2) reported the prevalence, incidence, or natural history of IBS; and 3) was in full manuscript publication form. Studies were excluded if they were conducted in various highly selected populations (e.g., patients with diabetes mellitus or pregnant women).

Data Extraction

Eligible articles were investigated by two reviewers. To explore the prevalence of IBS in Iran, information about gender distribution, their mean age and the reported prevalence were extracted from articles. Data in relation to the first author, province and district of the study, diagnostic definition of IBS (e.g., Manning criteria, Rome I criteria), sampled population, sample size, and case ascertainment methods to identify IBS patients (e.g., face-to-face interviews, mail surveys) were extracted too (Table 1).

Table1

Prevalence of Irritable Bowel Syndrome in Iranian Studies

RESULTS

Search Results

Details of the search in electronic databases are presented in figure 1. Searching PubMed and Google Scholar led us to 10 and 24 further suitable articles, respectively. In addition, fourteen relevant studies were found using Scientific Information Database and IranMedex. After excluding several articles by reading their full texts, 28 articles remained and we applied them in our study. However, 5 of them were found to be duplicate studies.[1325-28] Three of the identified studies were conducted in highly selected populations,[29-31] and in two articles, studied popula-tions were adolescents.[3344] Consequently, after final evaluation and considering the overlapping articles which were found in different databases, 18 articles were included in the systematic review.[10-12143234-4345-47] Characteristics of the reviewed articles (first author, place of study, study population, sample size, definition criteria, gender distribution, mean age of population, and IBS prevalence) are summarized in table 1 (dissimilarities in methodology were not taken into consideration).

Figure 1

Diagram of the searches for articles to be included in the systematic review of irritable bowel syndrome in Iran

The earliest study was published in 1997, in which Manning criteria were employed for diagnosing IBS patients.[3248]

Settings

Ten studies were conducted in Tehran province.[10-121438414245-47] Two studies were conducted in Northern provinces of Iran,[3943] three in the west[34-36] and three studies were performed in Fars Province which is located in south of Iran.[323740]

Definition criteria

The majority of studies used Rome II criteria to diagnose IBS.[111434-37394042434547] Manning,[32] Rome I[1012] and Rome III criteria[38] were also employed. In a study carried out by Yarandi et al. subjects were diagnosed with IBS by fulfilling either Rome II or Rome III criteria.[46] In one study, no definition criteria were mentioned and patients were diagnosed with IBS after ruling out organic conditions.[41]

Prevalence of IBS by gender

In eleven of the fourteen studies that presented the data by gender, a significant correlation between gender and IBS was observed. In 9 studies, there was marked female predilection,[10-1237-39424345] but male preponderance was described only by two studies.[3647] Amini et al. re-ported that IBS was more prevalent among males (20.2% vs. 8.2%). Likewise, Hosseini-Asl et al. found male preponderance.[36] Bagheri Lankarani et al. found that the prevalence of IBS in women was higher than in men (17.3% vs. 13%); however, the difference was not statistically significant.[32] In another study, the of femalemale ratio of IBS patients was 2.5:1 (1.5% versus 0.6%).[38]

Age and Prevalence of IBS

Except one study, all others reported the mean age of studied population.[41] Hatami et al. reported that prevalence of IBS in individuals older than 55 years was less than those who were younger; however, this difference was not statistically significant.[12] In Ghannadi et al.'s study, IBS was more prevalent in 1st and 2nd year compared to 4th and 5th year medical students. This finding can be due to the students’ adaptation to a new environment with difficult situations and the effect of this factor on their health.[39] However, in another study in Shiraz, the prevalence of IBS increased with advancing age among medical students. There was also a significantly increased prevalence of IBS in 4th year students, and the least prevalence was noted among 1st year students (26% vs. 9.6%).[32] Overall, it seems that there is a minimal difference in IBS prevalence within different age groups.

IBS Subtypes

Only three studies reported the prevalence of IBS by its subtypes.[123443] In a study conducted in Golestan University of Medical Sciences in 2005-6, individuals meeting the Rome II criteria for IBS were further divided into subgroups based on their bowel symptoms. In this study, 81.6% of patients were affected by constipationpredominant IBS , 6.1% had diarrhea-predominant IBS, and 12.2% did not meet the criteria for either constipation or diarrhea sub-type.[43] Ghannadi et al. showed that of individuals with IBS, 50% had constipation-predominant IBS and 29% fulfilled the criteria for diarrhea-predominant IBS. Additionally, in this study 21% of subjects suffered from both constipation and diarrhea alternatively.[34] Hatami et al. found that 20.1%, 15%, and 7.2% of IBS patients suffered from diarrhea-predominant, constipation-predominant, and alternating subtype, respectively.[12]

Prevalence of IBS in Iran

Studies that considered the prevalence of IBS in Iran, showed widely distinct estimates. The reported prevalence of IBS ranged from a low of 1.1% to a high of 25%. In the only study that used Manning criteria, its prevalence was estimated to be 16.4% among medical students.[32] The lowest prevalence of IBS that reported in Iran was 1.1%. In this study, Rome III criteria were used in 18180 individuals who living in four cities of Tehran province plus a small part of Tehran (including countrysides and rural areas).[38] Ganji et al. stated the highest prevalence of IBS in Iran. They employed Rome II criteria, and reported the prevalence of IBS in outpatients visiting a gastrointestinal clinic in Tehran was 25%.[14]

DISCUSSION

According to the 18 epidemiological studies that were included in the present systematic review, the prevalence of IBS in Iran varied from 1.1% to 25%. Several issues may contribute to such a wide range. An important factor that should be taken into account is the use of different diagnostic criteria for IBS. As previously mentioned, Manning criteria was employed only in one study, and the majority of Iranian studies used different versions of Rome criteria. For instance, Mahmoudi et al. reported that the prevalence of IBS among 3008 students of Tehran University was 4.2%, based on Rome I criteria. However, another study in this population using Rome II criteria reported a prevalence of 4.75%.[1011] In one study in New Zealand, the reported prevalence of IBS based on Manning 2, Manning 3, Rome I, and Rome II criteria was 16.2%, 9.7%, 5.6%, and 5.1%, respectively.[49] In another study In Korea, the prevalence of IBS was 8% and 9% based on Rome II and Rome III criteria, respectively. Authors of this study concluded that the Rome III criteria are less restrictive and they have fine agreement with the Rome II criteria.[50] Since Rome II criteria demand patients to report their symptoms over a longer period comparing to the Rome III, a higher number of patients will be diagnosed with IBS using Rome II.[51] The majority of Iranian studies were conducted before Rome III criteria were proposed and only three studies used Rome III criteria.[384546] We recommend employing Rome III criteria in future epidemiological studies.

Differences in sampled population may be another reason for the wide range of reports on the prevalence of IBS in Iran. For instance, Hatami et al. determined the prevalence of IBS among blood donors in Tehran.[12] Moreover, only University students were included in many studies.[1025263943]

The role of differences in socioeconomic status and cultural differences should be also taken into account. It is believed that the prevalence of IBS is less in developing countries compared to western countries.[552] However some Asian studies have reported high prevalence rates of IBS.[5354]

Prevalence of IBS in Iranian studies was different between females and males. Based on these studies, the prevalence of IBS in women was 1.5-17.3%, while in men it was 0.6-20.2%. Several studies did not report their results in each sex separately. More than half of reviewed studies in the present systematic review demonstrated that prevalence of IBS has statistically significant correlation with gender;[10-1236-39424347] but four studies were the opposite.[32344045] Only two studies showed that IBS was more prevalent in men.[3647] Similarly, in India, IBS was reported to be more prevalent in men than in women.[5556] In a study in Bangladesh, no significant difference was reported between genders.[54] Worldwide, most studies especially those conducted in western countries showed that IBS affects women more than men.[15758]

The majority of studies performed in Iran showed that there was no relation between age and prevalence of IBS. Khademolhosseini et al. reported that the prevalence of IBS was higher in the range of 33 to 45 yeas old.[37] Several studies which carried out in other countries reported that the prevalence of IBS decreases with age.[59-62] Since most of the included studies were not population-based, we were not able to conclude in which age group IBS was more or less prevalent.

In Iranian studies, no relation was found between prevalence of IBS and educational level. Worldwide studies on this issue presented controversial results.[863-65]

There was no relation between marital status and IBS in Iran. Only one study reported that married subjects were more likely to have IBS compared to singles, widows or divorced individuals.[38]

IBS is the most costly disorder among all FGIDs. Moghimi Dehkordi et al. estimated the total 6-month cost of Iranian IBS patients to be about PPP$160 (purchasing power parity dollars). IBS patients had the highest percentage of drug consumption and the duration of their absence from work was higher (2.26 days) in comparison with other FGID patients.[66]

Until now, no study has investigated the natural history of IBS in Iranian population. In addition, there are not enough population-based studies in order to assess the epidemiological aspects of IBS in Iran.

CONCLUSION

Estimated prevalence of IBS in Iran has a wide range. Since there is not enough literature on the incidence and natural history of IBS in Iranian population, efforts should focus on developing well-designed studies to investigate the epidemiology of irritable bowel syndrome and ideally, these studies should be community based. Because of the high prevalence of IBS and its considerable economic burden on Iranian population, researchers should concentrate on etiology of IBS and try to plan preventive programs in future studies.