Irritable bowel syndrome (IBS), a common chronic disorder of gastrointestinal function with no identifiable structural or metabolic cause, affects approximately 10%-20% of the general population and is associated with substantial health and societal burdens.
IBS is characterized by continuous or remittent abdominal pain associated with altered bowel habits, bloating, and diarrhoea or constipation (or both) and profoundly affects the patient’s quality of life (QoL).
IBS is categorised into three subtypes (IBS with Diarrhoea predominance (IBS-D), Constipation-predominant (IBS-C) and Alternating (IBS-A)).
Introduction Irritable bowel syndrome (IBS) is a common, chronic disorder of gastrointestinal function that has no identifiable structural or metabolic cause and that is characterized by continuous or remittent abdominal pain associated with altered bowel habits, bloating, and diarrhoea or constipation (or both, alternating between the two).(Mertz 2003) IBS with diarrhoea predominance (IBS-D) is one of two categories of IBS recognised by the Rome II criteria.(Thompson, Longstreth et al. 2000) The other category is IBS with constipation-predominance (IBS-C). Furthermore, some patients develop a mixed pattern of IBS (IBS-M) whereby they alternate between diarrhoea- and constipation-predominant symptoms.
IBS is one of the most common functional gastrointestinal disorders, affecting an estimated 10% to 20% of the population in developed countries.(Müller-Lissner, Bollani et al. 2001; Drossman, Camilleri et al. 2002; Torii and Toda 2004) The real prevalence may be higher, as it is believed that many patients suffer in silence or that IBS is underdiagnosed.(Hungin, Whorwell et al. 2003) IBS appears to be equally common in European, Asian and American countries, with similar prevalence rates among different ethnic groups (specifically, blacks, whites and Hispanics).(Drossman, Camilleri et al. 2002; Mach 2004) Approximately twice as many women as men are diagnosed with IBS; however, this discrepancy may be due to more females seeking medical care.(Müller-Lissner, Bollani et al. 2001; Locke 2003; Heitkemper, Jarrett et al. 2004)
Quality of Life
IBS is a chronic and bothersome disorder, and its symptoms, although not life-threatening, have a profound negative impact on quality of life (QoL), interfering with social activities, relationships, and work.(Hulisz 2004) Indeed, the distress caused by IBS has been likened to that associated with inflammatory bowel disease or asthma,(Frank, Kleinman et al. 2002; Pace, Molteni et al. 2003) and individuals with IBS reportedly have a poorer QoL than patients with diabetes mellitus or renal impairment.(Gralnek, Hays et al. 2000) The degree to which IBS reduces quality of life appears to be directly related to symptom severity and intensity.
Healthcare and societal burden IBS imposes a substantial economic burden in terms of both direct and indirect medical costs. It is associated with frequent visits to healthcare professionals, extensive diagnostic workups, and long-term or recurrent treatment costs. IBS accounts for 12% of patients seen in primary care practice and is the largest diagnostic group seen in gastrointestinal practice.(Drossman, Camilleri et al. 2002)
In the USA, where IBS is responsible for 2.4–3.5 million physician visits/year,(Drossman, Camilleri et al. 2002) the annual cost of treatment has been estimated to be between $1.7 billion and $10 billion in direct medical costs (excluding prescription over-the-counter) and $20 billion in indirect costs. The costs incurred by IBS are also high in Europe, with average medical costs of €71.8 per month per patient in France and an additional €185 per patient per year on top of average medical costs in the UK primary healthcare system.(Akehurst, Brazier et al. 2002)
Indirect societal costs, although less tangible, are also high, due to absenteeism from work, lost productivity, and personal expenses relating to decreased quality of life.(Boivin 2001; Leong, Barghout et al. 2003; Le Pen, Ruszniewski et al. 2004)
Natural history of IBS
IBS follows a chronic relapsing course that may begin in childhood, adulthood or later life, although it is not often seen for the first time in individuals older than 50 years.(Coremans 1999; Mertz 2003) The disease process of IBS is generally protracted and many patients become symptomatic again years after the initial diagnosis.(Thompson 2002) At any one time, approximately one-third of patients suffer from IBS with diarrhoea predominance.(Müller-Lissner, Bollani et al. 2001; Crowell 2004)
Executive Summary
