Broadening the horizon on IBS
Although irritable bowel syndrome (IBS) occurs worldwide, its prevalence, presenting symptoms and clinical management vary among countries and regions. The World Gastroenterology Organisation (WGO) recently convened an international panel of experts to assess these differences, provide a global perspective on IBS and identify areas for further study.
Lucinda A. Harris, M.D., of Mayo Clinic in Arizona, says developing a clinically useful and globally relevant definition of the disorder was a primary goal of the WGO task force.
"Most of the literature and diagnostic criteria for IBS come from the Western world," she points out. "The Rome criteria, now in their third iteration, have been trying to evolve a standard for use in IBS trials, but are not widely used clinically, especially outside North America and Western Europe."
The Rome III definition of IBS links symptoms such as abdominal pain or discomfort with changes in stool frequency and consistency that occur within a specific time frame — currently three months of symptoms, with symptoms having been present for at least six months. In contrast, the WGO practice guideline defines IBS as abdominal pain or discomfort associated with a change in bowel habits in which bloating, distention and disordered defecation are common features.
Based on the new definition, the WGO task force drafted three action statements. One emphasized the need for accurate translation of IBS symptoms into other languages. For example, although bloating and distension aren't interchangeable terms in English, other cultures may not discriminate between the two. Such linguistic divergence can lead to a number of problems, including, in some cases, misdiagnosis.
"It's important to explore and understand symptoms in non-English-speaking cultures," Dr. Harris says. "That must be accomplished before anything else."
The WGO task force also recommended exploring approaches to subclassification of IBS different from those identified by Rome III, which now include IBS with diarrhea, IBS with constipation, IBS mixed type and IBS unsubtyped.
"Subclassification by bowel type may not be the only way to look at this because, as is the case with other gastrointestinal symptoms, perceptions and descriptions of bowel habits vary in different cultures and languages," Dr. Harris notes. "Frequency, consistency and ease of defecation are important in distinguishing abnormal from normal bowel movements, but other aspects of clinical presentation are also important. It might be more useful to talk about IBS with predominant bowel dysfunction or IBS with predominant bloating or to describe the disorder in terms of precipitating factors such as post-infectious IBS, food-induced IBS, and menstrual- or stress-related IBS."
She adds, "A certain percentage of patients have post-infectious IBS, making it important to consider the role of flora both inside and outside the gut. The increasing evidence about the importance of the microbiome shows the value of other approaches to the subclassification of IBS."
Demographics, comorbidities and impact
The WGO group also called for a comprehensive global map of IBS, detailing variations in demographics, comorbidities and effect on quality of life.
For instance, although global differences in IBS prevalence exist, a comparison of prevalence data is complicated by different methodologies, diagnostic criteria and study locations.
"Prevalence ranges from 1.1 to 22 percent, with the median being 5 to 15 percent," Dr. Harris says. "But so much depends on access to health care. In the West, more women than men seek medical attention for IBS — sometimes by a ratio of as much as 4 to 1 — and this seems generally true in Korea and Japan, too. But on the Indian subcontinent, twice as many men as women go to the doctor, and men account for up to 80 percent of those diagnosed with IBS."
Despite these variations and large gaps in data in parts of Latin America, Africa and Asia, prevalence rates seem fairly similar worldwide. China is a notable exception, with reported rates of 1 percent.
The significant, and often underestimated, impact of IBS on quality of life also seems relatively consistent throughout the world. It's less clear whether the comorbidities associated with IBD in the West — functional dyspepsia, gastroesophageal reflux disease, noncardiac chest pain, anxiety, depression, chronic pain, fibromyalgia — are common elsewhere.
Dr. Harris stresses that a global understanding of IBS is crucial for better assessment and management of the disorder. "If we understand how IBS presents throughout the world, we may learn more about the role of gut microbes and gain an increased awareness of how IBS affects quality of life. We may also learn what factors trigger symptoms and how patients respond to treatment with diet, exercise, rest, cognitive behavioral therapy and medications that we currently have and are developing," she says.