2023 Impact Factor
2023 Impact Factor
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.Irritable bowel syndrome (IBS) is a symptom complex involving abdominal pain, bloating, diarrhea, and constipation, and leads to a substantial reduction in quality of life.1 Although IBS is not life-threatening, it has significant socioeconomic consequences. Outpatient and primary care physician visits and medication costs are particularly increased for patients with IBS.2 Work-ability impairment is another substantial concern; as IBS symptom severity increases, the degree of work-ability impairment also increases.3 Thus, IBS poses a considerable burden on both healthcare services and society.
IBS prevalence has been previously studied. A Rome Foundation working team performed a literature review and reported the global IBS prevalence in adults to be 8.8% (8.7-8.9%). However, regional heterogeneity was observed with respect to IBS prevalence in each study region as follows: 17.5% (16.9-18.2%) in Latin America, 9.6% (9.5-9.8%) in Asia, 7.1% (8.0-8.3%) in North America/Europe/Australia/New Zealand, and 5.8% (5.6-6.0%) in the Middle East and Africa.4 In Asian countries, IBS prevalence ranges from 1.1% in Iran to 21.2% in Japan. The prevalence of IBS subtypes also varies.5 The reasons for this heterogeneity are suspected to be multifactorial.
Some factors are associated with differences in study methods. One methodological factor is the difference in the IBS criteria used in each study. Olafsdottir et al6 compared IBS prevalence according to the Manning criteria, Rome II, and Rome III in the same participants (799 Icelandic inhabitants in the age range of 18-75 years) and reported that the prevalence varied according to the criteria followed: Manning criteria, 32%; Rome III, 13%; and Rome II, 5%.
Another methodological factor is the heterogeneity of participants’ sex and age. Previous studies have indicated that female and younger individuals have a higher risk of IBS. A recent study revealed that IBS prevalence was higher in females than in males with a female-to-male odds ratio of 1.8 (1.7-2.0). IBS prevalence decreases with age, and the prevalence in individuals aged 18-39 years, 40-64 years, and > 65 years is 5.3% (5.0-5.6%), 3.7% (3.5-4.0%), and 1.7% (1.4-1.9%), respectively.7
Even when uniform symptom-based criteria are applied based on an identical methodology to define IBS presence, the prevalence varies substantially among countries.8 Psychosocial (stress, illness, behavior, and diet) and biological (genetic variation, infection, gut microbiota, and immune activation) factors are suspected to affect IBS pathogenesis and cause regional variations.9 In Asian populations, IBS is equally prevalent in male and female individuals, and IBS with diarrhea (IBS-D) is more prevalent.5 However, Asia is too multi-environmental, multiethnic, and multicultural to evaluate as a single entity. Therefore, an IBS survey in separate smaller areas with similar features within Asia is necessary. In this study we had focused on East Asian 3 countries, Japan, China, and South Korea. These 3 countries have some similarities in ethnicity, food culture (rice-based diet, chopstick use, etc), and rapid economic growth, while they have their own unique cultures. Because IBS is a serious healthcare problem in east Asia, estimating and comparing IBS prevalence in these areas is meaningful.
In this study, we aim to investigate IBS prevalence in the urban populations of 3 East Asian countries (Japan, South Korea, and China) after adjusting for sex and age following the same criteria and compare the IBS features among these 3 countries.
Data collection was performed as a part of a large research project at our institution. Data from Japan, South Korea, and China on IBS prevalence were extracted from the data of this project.
We conducted an online cross-sectional survey of residents of Japan, South Korea, and China from March 2016 to February 2018. The Japanese Society of Gastroenterology recommends the Rome criteria.10 The use of the Rome criteria can reduce heterogeneity across patients with IBS and help in diagnosis without the need for clinical examinations.11,12 Since the Rome IV criteria were published in June 2016, we used the Rome III criteria. The study participants were selected from among approximately one million people who anonymously registered with a leading Japanese website research company’s (Macromill, Inc, Tokyo, Japan) web panel. An equal number of participants, with an equal gender distribution, were assigned to each age group, ranging in age from the 20s to the 60s. This study conformed to the ethical guidelines of the Helsinki Policy Statements. Participants were informed of the research aim and the intended use of the survey data and were guaranteed anonymity if they decided to participate. Individuals who agreed to the stated procedures and conditions were included. Next, providing informed consent, the participants answered demographic questions. Thereafter completing the questionnaires, each of them received approximately 50 cents United States currency as pay for their participation through the Macromill, Inc., system. Although individual data points were acquired through an internet research company, data from this study were not so deviated from public population. Regarding data availability, all relevant data are included in this paper.
The countries surveyed were Japan, China, and South Korea; participants were men and women in their 20s-60s (Table 1). The ratio of men to women in each age group was maintained to be identical. We selected residents of urban areas as participants to minimize the international heterogeneity inherent to an internet environment, hygienic levels, and other social factors. The survey area in South Korea included only Seoul and targeted 820 individuals. The survey area in China included only Beijing and targeted 1030 individuals. The survey areas in Japan included Tokyo and Fukuoka and targeted 1030 individuals in Tokyo and 1030 in Fukuoka.
Table 1 . Participant Characteristics in Japan, China, and South Korea
| Age | Japan | China | South Korea | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| All | Male | Female | All | Male | Female | All | Male | Female | |||
| Twenties | 452 | 216 (43.2-52.4) | 236 (47.6-56.8) | 242 | 120 (43.3-55.8) | 122 (44.2-56.7) | 183 | 93 (43.6-58.0) | 90 (42.0-56.4) | ||
| Thirties | 372 | 196 (47.6-57.7) | 176 (42.3-52.4) | 170 | 86 (43.1-58.0) | 84 (42.0-56.9) | 145 | 71 (41.0-57.0) | 74 (43.0-59.0) | ||
| Forties | 412 | 206 (45.2-54.8) | 206 (45.2-54.8) | 206 | 103 (43.2-56.8) | 103 (43.2-56.8) | 164 | 82 (42.4-57.6) | 82 (42.4-57.6) | ||
| Fifties | 412 | 206 (45.2-54.8) | 206 (45.2-54.8) | 206 | 103 (43.2-56.8) | 103 (43.2-56.8) | 164 | 82 (42.4-57.6) | 82 (42.4-57.6) | ||
| Sixties | 412 | 206 (45.2-54.8) | 206 (45.2-54.8) | 206 | 103 (43.2-56.8) | 103 (43.2-56.8) | 164 | 82 (42.4-57.6) | 82 (42.4-57.6) | ||
| All | 2060 | 1030 | 1030 | 1030 | 515 | 515 | 820 | 410 | 410 | ||
| Mean age ± SD | 44.5 ± 14.1 (43.9-45.1) | 44.6 ± 14.1 (43.8-45.5) | 44.4 ± 14.1 (43.6-45.3) | 43.7 ± 13.4 (42.9-44.5) | 43.7 ± 13.4 (42.5-44.8) | 43.7 ± 13.5 (42.5-44.9) | 44.6 ± 13.5 (43.7-45.5) | 44.8 ± 13.6 (43.4-46.1) | 44.4 ± 13.3 (43.1-45.7) | ||
Data are expressed as n or n (95% CI).
The 95% CI for the prevalence is in parentheses.
The Rome III criteria for IBS were used in this study. These criteria include recurrent abdominal pain or discomfort (experienced for at least 3 days per month in the previous 3 months) associated with 2 or more of the following characteristics: (1) symptom improvement after defecation, (2) symptom onset associated with a change in defecation frequency, and (3) symptom onset associated with a change in stool form (appearance). Subtypes were based on stool consistency and included IBS with constipation (IBS-C), IBS-D, mixed IBS (IBS-M), and unclassified IBS (IBS-U). The Japanese,13 Korean,14 and Chinese15 versions of the Rome III questionnaires have been validated for reliability and validity.
First, the chi-square test was performed to examine the IBS prevalence and subtypes in East Asia with respect to sex and age. Next, the same test was used to compare IBS prevalence and subtypes among Japan, China, and South Korea. Afterward, we calculated the adjusted residuals to examine the difference between the observed and expected frequencies in an affected person. Furthermore, the prevalence of different IBS subtypes was calculated for Japan, China, and South Korea. IBM SPSS Statistics 24 (IBM Corp, Armonk, NY, USA) was used for statistical analysis.
The study protocol was approved by the Ethics Committee of Kyusyu University (Approval No. 16-001), and all participants provided informed consent. All authors had access to the study data and reviewed and approved the final manuscript.
As individual datapoints were acquired through an internet research company, data from this study are not appropriate for public deposition. Regarding data availability, all relevant data are included in this paper.
IBS prevalence in East Asia was 12.6% (95% confidence interval [CI], 11.6-13.7) (Table 2). The prevalence of IBS-D, IBS-C, IBS-M, and IBS-U in East Asia was 2.8% (95% CI, 2.3-3.3), 2.1% (95% CI, 1.7-2.6), 6.0% (95% CI, 5.3-6.8), and 1.7% (95% CI, 1.4-2.2), respectively.
Table 2 . Prevalence of Irritable Bowel Syndrome Subtypes in East Asia
| Rome III | All | Sex | Age group | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Males (n = 1955) | Females (n = 1955) | χ2 ( | Twenties (n = 877) | Thirties (n = 687) | Forties (n = 782) | Fifties (n = 782) | Sixties (n = 782) | χ2 ( | |||||
| IBS | 492 12.6 (11.6-13.7) | 272 13.9 (12.5-15.5) | 220 11.3 (9.9-12.7) | 6.29 (1) | 0.012 | 110 12.5 (10.5-14.9) | 86 12.5 (10.3-15.2) | 123a 15.7 (13.4-18.5) | 103 13.2 (11.0-15.7) | 70b 9.0 (7.1-11.2) | 16.66 (4) | < 0.002 | |
| % | |||||||||||||
| IBS-D | 108 2.8 (2.3-3.3) | 73 3.7 (3.0-4.7) | 35 1.8 (1.3-2.5) | 13.75 (1) | < 0.001 | 20 2.3 (1.5-3.5) | 15 2.2 (1.3-3.6) | 34a 4.4 (3.1-6.0) | 25 3.2 (2.2-4.7) | 14 1.8 (1.1-3.0) | 12.24 (4) | 0.016 | |
| % | |||||||||||||
| IBS-C | 81 2.1 (1.7-2.6) | 34 1.7 (1.4-2.4) | 47 2.4 (1.8-3.2) | 2.13 (1) | 0.144 | 12 1.4 (0.8-2.4) | 10 1.5 (0.8-2.7) | 19 2.2 (1.6-3.8) | 18 2.3 (1.5-3.6) | 22 2.8 (1.9-4.2) | 6.24 (4) | 0.182 | |
| % | |||||||||||||
| IBS-M | 235 6.0 (5.3-6.8) | 128 6.6 (5.5-7.7) | 107 5.5 (4.6-6.6) | 2.00 (1) | 0.158 | 70a 8.0 (6.4-10.0) | 52 7.6 (5.8-9.8) | 53 6.8 (5.2-8.8) | 41 5.2 (3.9-7.0) | 19b 2.4 (1.6-3.8) | 28.37 (4) | < 0.001 | |
| % | |||||||||||||
| IBS-U | 68 1.7 (1.4-2.2) | 37 1.9 (1.4-2.6) | 31 1.6 (1.1-2.2) | 0.54 (1) | 0.463 | 8c 0.9 (0.5-1.8) | 9 1.3 (0.7-2.5) | 17 2.2 (1.4-3.5) | 19 2.4 (1.6-3.8) | 15 1.9 (1.2-3.1) | 7.44 (4) | 0.114 | |
| % | |||||||||||||
aThe observed frequency is significantly higher than the expected frequency at the 1% level.
bThe observed frequency is significantly lower than the expected frequency at the 1% level.
cThe observed frequency is significantly lower than the expected frequency at the 5% level.
IBS, irritable bowel syndrome; IBS-D, irritable bowel syndrome with diarrhea; IBS-C, irritable bowel syndrome with constipation; IBS-M, mixed irritable bowel syndrome; IBS-U, unclassified irritable bowel syndrome.
The 95% CI for the prevalence is in parentheses.
There were significant differences in IBS prevalence and IBS-D between the sexes (Table 2). In contrast, there were no significant differences in IBS-C, IBS-M, and IBS-U prevalence between the sexes.
There were significant differences in the prevalence of IBS, IBS-D, and IBS-M across the age groups (Table 2). In addition, among individuals with IBS, the observed frequency was 1% higher than the expected frequency in participants in their 40s, and the observed frequency was 1% lower than the expected frequency in participants in their 60s (adjusted residual: 3.0,
There were significant differences in the prevalence of IBS, IBS-D, IBS-M, and IBS-U (Table 3). In addition, for patients with IBS in Japan and South Korea, the observation frequency was 1% higher than the expected frequency, and for those in China, the observation frequency was 1% lower than the expected frequency (adjusted residual: 4.6,
Table 3 . Prevalence of Irritable Bowel Syndrome Subtypes in Japan, China, and South Korea
| Japan (n = 2060) | China (n = 1030) | South Korea (n = 820) | χ2 ( | ||
|---|---|---|---|---|---|
| IBS | 307a 14.9 (13.4-16.5) | 57b 5.5 (4.3-7.1) | 128a 15.6 (13.3-18.3) | 63.44 (2) | < 0.001 |
| % | |||||
| IBS-D | 78a 3.8 (3.0-4.7) | 10b 1.0 (0.5-1.8) | 20 2.4 (1.6-3.7) | 20.67 (2) | < 0.001 |
| % | |||||
| IBS-C | 45 2.2 (1.6-2.9) | 15 1.5 (0.9-2.4) | 21 2.6 (1.7-3.9) | 3.02 (2) | 0.221 |
| % | |||||
| IBS-M | 160a 7.8 (6.7-9.0) | 27b 2.6 (1.8-3.8) | 48 5.9 (4.44-7.68) | 32.23 (2) | < 0.001 |
| % | |||||
| IBS-U | 24b 1.2 (0.8-1.7) | 5b 0.5 (0.2-1.1) | 39a 4.8 (3.5-6.4) | 57.12 (2) | < 0.001 |
| % |
aThe observed frequency is significantly higher than the expected frequency at the 1% level.
bThe observed frequency is significantly lower than the expected frequency at the 1% level.
IBS, irritable bowel syndrome; IBS-D, irritable bowel syndrome with diarrhea; IBS-C, irritable bowel syndrome with constipation; IBS-M, mixed irritable bowel syndrome; IBS-U, unclassified irritable bowel syndrome.
The 95% CI for prevalence is in parentheses.
On assessing the prevalence of IBS subtypes in Japan, China, and South Korea, IBS-M had the highest prevalence in all 3 countries (52.12%, 47.37%, and 37.50%, respectively) (Figure). In contrast, IBS-U had the lowest prevalence in Japan and China, and IBS-D had the lowest prevalence in South Korea (7.82%, 8.77%, and 15.63%, respectively).
Figure 1. Proportions of irritable bowel syndrome (IBS) subtypes in Japan, China, and South Korea. Numbers represent percentages. IBS-D, IBS with diarrhea; IBS-C, IBS with constipation; IBS-M, mixed IBS; IBS-U, unclassified IBS.
We investigated the prevalence of IBS in urban populations in Japan, South Korea, and China. To minimize the methodological bias, the participants in this internet survey were recruited randomly and were matched for sex and age in each country. The overall prevalence of IBS defined according to the Rome III criteria in the 3 countries was 12.6% (95% CI, 11.6-13.7). IBS prevalence in China was statistically lower than those in Japan and South Korea. This study compared the citizens of similar urbanized Asian cities. However, we observed differences in IBS prevalence. Regarding IBS subtypes, IBS-M was the most common, followed by IBS-D, IBS-C, and IBS-U in the overall analysis. IBS-M was the most common subtype in all 3 countries; however, the second most common subtype was IBS-D in Japan, IBS-C in China, and IBS-U in South Korea.
According to an internet survey that adopted the Rome III criteria, the prevalence of IBS was estimated to be 10.1% in the world population, 9.3% in Japan, and 7.4% in China (South Korean data were not shown).8 IBS prevalence is reported to be higher in young and female individuals.8 The prevalence rate in the present study was found to be slightly higher compared to those previously reported. Some reports have indicated that IBS is more prevalent in urban areas than in the countryside.16,17 The study population of this study included the residents of cities with a population of over a million individuals. This is one important reason for the higher prevalence observed in this study.
Regarding sex differences, in our study, IBS prevalence, especially IBS-D prevalence, was higher in male participants. However, a meta-analysis studying the worldwide IBS prevalence showed a higher IBS prevalence in female individuals, although the difference in Asia was not significant, unlike that in Western countries and other regions.4 Sex differences in IBS prevalence showed regional heterogeneity. A higher prevalence of IBS-D in male individuals has also been reported by previous studies, in line with our results.18,19
In our study, IBS prevalence was highest in individuals in their 40s and lowest in those in their 60s. Subtype analysis showed that IBS-D was most prevalent in individuals in their 40s. IBS-M was most prevalent in individuals in their 20s, and its prevalence gradually decreased with age. No significant difference in IBS-C was observed with respect to age. In previous large-scale international population-based studies and meta-analyses, IBS prevalence was reported to be lower in individuals aged 50 years or older than in those younger than 50 years.4,20,21 This finding is consistent with our results. However, the age group showing the highest IBS prevalence has not been determined; the relationship between the prevalence of the IBS subtype and age remains to be elucidated in the future. However, aging is suspected to affect alterations in bowel motility and the gut microbiota.22
Among the 3 countries, the prevalence was comparable in Japan and South Korea but significantly lower in China. A similar trend was observed in other studies using the Rome III criteria.8 However, the recent Rome Foundation Global Study7 found that when IBS was diagnosed based on the Rome IV criteria, the difference in IBS prevalence between China and Japan (lower IBS prevalence in China) was no longer significant.7 Three principal changes were introduced in the Rome IV criteria: elimination of the symptom discomfort from the question on abdominal pain, changes in the criteria on the relationship between pain and stools, and increase in the minimum frequency of pain to once a week. In a Japanese internet survey, the number of patients with IBS-C diagnosed using the Rome III criteria decreased by one-fourth when compared with the number diagnosed using the Rome IV criteria, and most of the remaining patients were classified as having unspecified functional bowel disorders.23 A similar tendency was reported in China.24 It is presumed that abdominal discomfort or frequency of pain influenced this international heterogeneity.
There is a possibility that other factors influenced our result. According to previous studies, the Chinese IBS nationwide prevalence diagnosed with Rome III criteria was 7.4%. However, heterogeneity depending on cities (3.2% in Xi’an, 5.9% in Hangzhou, 7.6% in Changzhou, and 15.8% in Shanghai) was observed.25 A meta-analysis suggested that a history of acute gastrointestinal infection, food allergies, alcohol consumption, and anxiety/depression were significant IBS risk factors among the Chinese.26 Whether our observation of low IBS prevalence in Beijing was due to regional heterogeneity or some underlying factors is uncertain.
A systemic review of global IBS prevalence, including 102 177 participants, reported IBS prevalence subtypes according to the Rome III criteria.8 When pooling data from the studies, 33.8% (95% CI, 27.8-40.0; I2 = 98.1%) of participants had IBS-M, 27.8% (24.9-30.7; I2 = 91.5%) had IBS-D, 20.0% (16.7-23.4; I2 = 95.3%) had IBS-C, and 14.1% (10.0-18.8; I2 = 97.6%) had IBS-U. Our results regarding the IBS subtypes in the 3 countries were in line with the results of this global study. With regard to IBS subtype prevalence in each country, a recent report that estimated IBS prevalence based on experts’ experience from different medical institutions in several Asian countries showed similar prevalence of IBS subtypes in Japan, China, and South Korea.27 Naturally, data on the general population versus clinical experience should be interpreted with caution. Three studies reporting on IBS subtypes in Japan indicated that IBS-M prevalence was the highest, followed by IBS-D, IBS-C, and IBS-U in sequential order. In addition, IBS-D was more prevalent in male than in female individuals.28,29 These results were similar to the findings of this study. Reports on IBS subtypes diagnosed using the Rome III criteria in South Korea and China are limited. A phone interview survey including 1009 individuals aged 15 years or older in South Korea showed that IBS-C was the most prevalent (36.3%), followed by IBS-D (29.7%), IBS-M (22.0%), and IBS-U (12.1%).30 Two reports on IBS in the Chinese general population in South China (Hong Kong and Hangzhou) showed that IBS-D is the most prevalent IBS subtype.31
Currently, there is no diagnostic gold standard test or biomarker for IBS. IBS is diagnosed using symptom-based criteria. Because there are several IBS criteria, determining which should be applied in the setting of epidemiological research is crucial. In this study, the Rome III criteria were used in the urban population of 3 East Asian countries. Although the latest version of the Rome criteria is Rome IV, we used Rome III because our study started before the Rome IV criteria were released and validated in the Japanese, Korean, and Chinese languages. The switch from the Rome III to Rome IV criteria was reported to reduce the prevalence of IBS by half,7 and another study reported that the IBS prevalence is substantially lower with the Rome IV criteria than with the Rome III criteria.8 The Rome III criteria may involve higher sensitivity but lower specificity than the Rome IV criteria for IBS diagnosis.
There are some limitations to this study. First, we used internet-based surveying rather than a more traditional epidemiological survey methodology. However, the internet diffusion rate is high in these countries, and selection bias caused by using the internet is small. From a methodological viewpoint, an internet-based survey showed noninferiority; both internet-based and household surveys were performed in a global study, and the internet-based surveys provided more reliable estimates of prevalence rates because the internet survey achieved complete, accurate, and reliable data collection.7 However, because the individuals’ data were obtained through an internet research firm, pre-registered samples are generated through voluntary registration, which does not accurately reflect the population group of each country’s urban area. Second, participants were not evaluated based on procedures including colonoscopy. We could not completely exclude digestive symptoms of organic causes, which is a common limitation of populational studies. Third, the surveyed population was limited to the residents of urban areas. It is uncertain whether our results can be generalized to rural populations. IBS prevalence is reported to be higher in urban than in rural areas.16,17 Fourth, IBS pathogenesis is likely affected by many factors, including the living environment, socioeconomic status, education level, mental stress, and diet.9,32 For example, consumption of dietary fiber, a fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP) diet, and spicy foods33 is assumed to affect the pathophysiology of IBS. Furthermore, individual genetic factors or gut microbiomes relate to IBS. In this study, precise characteristic data of the participants was lacking. Studies that reveal a relationship between these multi-factors and IBS prevalence using appropriate analytical methods are needed in the future.
In this study, we performed an internet-based IBS prevalence survey based on the Rome III criteria in 3 East Asian countries: Japan, China, and South Korea. The overall IBS prevalence in these 3 countries was 12.6% (95% CI, 11.6-13.7), which was slightly higher than the reported global prevalence. IBS prevalence was highest in individuals in their 40s and lowest in those in their 60s. In previous reports, a higher IBS prevalence in female individuals was reported; however, in this study, male individuals had a higher prevalence of IBS, especially of IBS-D. On comparing the 3 countries, IBS prevalence was significantly lower in China than in Japan and South Korea. Although IBS-M was the most prevalent in all 3 countries, the prevalence of IBS subtypes varied across the countries. Further studies to elucidate the factors responsible for this regional heterogeneity are warranted.
This work was supported by Kyushu University Interdisciplinary Programs in Education and Projects in Research Development (P&P) (Grant No. 27819).
None.
Jun Tayama and Takuya Kimura designed this study and organized the data collection; Shintaro Hara and Toyohiro Hamaguchi conducted the statistical analysis; Atsushi Takeoka and Jun Tayama prepared the original draft; and Shintaro Hara, Jun Tayama, Takuya Kimura, Toyohiro Hamaguchi, and Shin Fukudo reviewed and edited the draft. All authors have read and approved the final manuscript’s submission for publication.
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