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Health Economics of IBS -- Clinical Implications

Posted 06/24/2005

Brooks D. Cash, MD, FACP

Introduction
Irritable bowel syndrome (IBS) is a chronic gastrointestinal (GI) disorder characterized by impaired regulation of GI function (motility and secretion) and altered visceral sensitivity, resulting in the typical physical manifestations of abdominal pain, bloating, and abnormal bowel habits. IBS is a highly prevalent disorder, and although it does not have a significant impact on mortality, there remains no definitive curative therapy. Thus, patients with this condition may suffer from debilitating symptoms for prolonged periods. The burden of illness on patients, the healthcare industry, and employers that is directly attributable to IBS has only recently begun to be realized. This article summarizes the scope of the economic burden associated with IBS and examines potential targets for cost containment through directed education, recognition, and effective treatment of patients with IBS.

Economic Burden of IBS
IBS is extremely common, with population-based prevalence estimates ranging from 10% to 15% in North America.[1-2] Approximately 12% of patients in the primary care setting and 28% of patients seeking subspecialty gastroenterology care will be diagnosed with IBS.[3-4] Several patterns of healthcare seeking have been identified in patients with IBS. Although IBS affects both sexes, it is largely considered a women's health issue. Epidemiologic data suggest that the female:male ratio of IBS sufferers in the community is 2-3:1, although estimates differ depending on the practice setting from which such assessments are generated. Generally, however, two thirds of IBS sufferers in North America who seek medical care are women.[5,6] Although the minority (25%) of individuals with typical symptoms of the disorder actually do seek medical care, the high prevalence of IBS translates into a sizable absolute number of patients.[2,7] Recent reports estimate physician visits attributable to IBS to be as high as 3.5 million visits annually.[8-10] Additionally, it has been repeatedly demonstrated that patients with IBS are more likely to seek medical care for other, non-GI conditions or physical complaints, such as fibromyalgia or chronic pelvic pain.[5] Because there are no discrete physical abnormalities or biochemical/serological markers that define IBS, this condition has historically been viewed by many clinicians as a diagnosis of exclusion. This view, coupled with the increasing number and cost of available diagnostic studies, can lead to extensive and unnecessary testing. An exhaustive exclusionary diagnostic evaluation, especially in patients with typical IBS symptoms without alarm features (age ≥ 50 years, fever, abnormal physical examination findings, hematochezia, unintentional weight loss, nocturnal symptoms, or a family history of organic GI disease), contributes to an increased burden on both patients and the medical system, and recently has been challenged regarding its usefulness in the management of such patients.[11]

Direct vs Indirect Costs
When considering the economic burden of a condition, it is important to consider both direct and indirect costs. The direct costs (use of healthcare-related services such as physician visits, diagnostic tests, and prescription or over-the-counter medication) associated with IBS are substantial.[12] Excluding prescription and over-the-counter medicines, direct costs have been estimated to range from $1.5 to $10 billion. The indirect costs of IBS, however, have been estimated to be much greater -- approaching $20 billion.[13] Examples of indirect costs include expenses that are not directly associated with the procurement of healthcare resources, such as the loss of hourly wages resulting from missed work or diminished work productivity resulting from absences for physician visits or incapacitating symptoms. Although direct costs are relatively straightforward and measurable, indirect costs are much more difficult to quantify.

Indirect costs comprise 3 primary components -- absenteeism (time absent from work), presenteeism (decreased productivity at work), and diminished health-related quality of life (HRQoL) -- which, in turn, are intangible costs that may result in diminished productivity.[12,14-16] The economic impact of absenteeism is fairly straightforward to gauge because most employers maintain adequate records of employee absences for illness. It has been estimated that a minimum of one third of IBS patients are absent on average from 1 day of work or school per week because of their symptoms.[17] Results of a recent survey indicate that patients with IBS were absent from work twice as many days per year due to illness as compared with healthy respondents.[18] In 1998 the direct cost of treating an employee with IBS was nearly $4000 compared with $2350 for an employee without IBS.[19] By comparison, indirect costs to the employer were approximately $470 higher for employees with IBS -- a likely underestimate because these indirect costs only included measures of absenteeism.[20]

Presenteeism may represent a significantly larger and less appreciated component of indirect costs than absenteeism.[17-21] Results of a recent study that examined impaired work productivity and HRQoL in employees with IBS demonstrated that the disorder was associated with a 21% reduction in work productivity, the equivalent of working less than 4 days in a 5-day work week.[14] Both absenteeism and presenteeism are growing concerns for both employers as well as interested consumers who are forced to bear the brunt of lost work productivity and subsidize employee healthcare costs. It is, therefore, critical for healthcare providers and managed care organizations to present solutions for employers on how best to manage the large, often unrecognized costs of IBS.

Finally, IBS has a significant negative impact on the HRQoL of affected patients[14,22-25] that is comparable to that of other chronic GI and non-GI disorders.[26-27] Reduction in HRQoL may result from several features of IBS that are also observed with other functional GI disorders. The multiple symptoms of IBS may wax and wane over time, leading patients to put off healthcare consultation, thus resulting in delayed diagnosis of, and extended time suffering from, the disorder.[12,28] Supporting this hypothesis is the observation that although multiple epidemiologic and clinical studies demonstrate that the symptoms of IBS typically appear between the ages of 15-30 years, most IBS patients do not seek their first healthcare consultation for the disorder until they are between the ages of 30 and 50 years, coinciding with peak employment ages.[29] Last, as in other functional GI disorders, the historical absence of effective therapies addressing the multiple symptoms of IBS is also likely have a negative impact on the HRQoL of affected patients.[30]

Clinical and Therapeutic Impact
What, then, can be done to mitigate some of the costs associated with IBS? Although it is not the focus of this column, accurate and timely diagnosis is an important consideration. For IBS, applying clinically proven symptom-based diagnostic criteria (Manning, Rome, Rome I, or Rome II) to make a positive, rather than exclusionary, diagnosis is an important step in the right direction to reduce overall costs. Previous analyses have demonstrated that in patients with suspected IBS who do not manifest alarm features, the pretest probability of organic disease is similar to that of the general population, suggesting that there is little to be gained by implementing exhaustive diagnostic evaluations in such patients.[11,31] Current recommendations for such patients are to initiate empiric therapy, reserving additional testing for nonresponsive patients.[1] There is evidence that this "minimalistic" approach is gaining favor and that such an approach can reduce resource utilization involving diagnostic procedures and frequent office visits.[30] The magnitude of the impact of this approach on the total costs associated with IBS, however, remains to be seen.

Regarding therapeutic interventions and minimization of the costs associated with IBS, it is becoming increasingly clear that the multiplicity of the symptoms may be as important a feature of the disorder as the severity of individual symptoms in terms of how patients report the "bothersomeness" or seriousness of their condition. A significant limitation of the so-called traditional therapies for IBS, such as bulking agents or antispasmodic medications, is that they only target single symptoms, a feature that may explain their absence of proven efficacy in randomized controlled trials. Alternatively, broader acting therapeutic agents or modalities that provide relief for the multiple symptoms of IBS would conceivably have promise in reducing multiple direct and indirect costs of this condition. In a study regarding the effects of psychotherapy in patients with severe IBS, Creed and colleagues[32] demonstrated annual healthcare-related utilization savings of nearly $700 compared with usual care. In this trial, "usual care" was defined as whatever management was considered appropriate by the gastroenterologists or primary care physicians caring for the patients. Although not explicitly delineated in the text of the article, "usual care" in this case, consisted primarily of traditional IBS therapies (such as antispasmodic agents, antidiarrheals, and bulking agents). However, the generalizability of these results to the community setting is not known. Fortunately, physicians now have access to new and increasingly effective medical therapies for the management of the multiple symptoms of IBS in the form of the serotonergic agents, tegaserod and alosetron. It is widely accepted that these agents are effective therapies for IBS; both tegaserod and alosetron were the only agents to receive grade A recommendations as IBS therapies from the American College of Gastroenterology Functional GI Disorder Task Force, based on the high quality of published evidence supporting their global efficacy in IBS with constipation and IBS with diarrhea, respectively.[1] However, although both tegaserod and alosetron are clinically effective, they have been associated with adverse effects. Tegaserod is reported to cause severe but transient diarrhea, whereas patients taking alosetron have reported episodes of ischemic colitis and severe constipation. Ischemic colitis has also been observed in the postmarketing experience with tegaserod, but the incidence rate of ischemic colitis in patients taking tegaserod appears to be similar to that observed in the general population and is actually lower than reported rates in IBS patients. Thus, a causal relationship between tegaserod and ischemic colitis has not been established.[33]

Although the expense associated with these newer agents may result in an initial increase in the direct costs of IBS care, it is possible that they could, when clinically effective for appropriate individual patients, significantly reduce the long-term direct and indirect costs. Limited data exist regarding the use of these serotonergic agents and their actual impact on the costs of IBS. A study utilizing a decision-analysis model examined the benefits of symptom improvement vs the complications associated with alosetron therapy in the treatment of patients with IBS with diarrhea.[33-34] It showed that although the benefit-to-risk profile of alosetron was favorable, this treatment was associated with a potentially large cost per quality-adjusted life-year. Currently, alosetron therapy is limited to women with severe IBS with diarrhea that is refractory to traditional therapies. As a consequence, new or ongoing studies regarding the economic impact of this therapy on IBS are limited. (In order to prescribe alosetron, clinicians must be familiar with the current prescribing guidelines and be enrolled in the prescribing program administered by the manufacturer. Patients who are prescribed alosetron are given a patient information booklet to read and are asked to sign a patient-physician agreement indicating that they have both read and understand the effects of the medication and that they do desire to take it.)

Largely due to the limited availability of data concerning the economic impact of the serotonergic agents in the treatment of IBS, a series of articles addressing many of the issues discussed in this column was recently published in The American Journal of Managed Care .[14,35-39] [14,34-38] The authors of these articles explore the costs associated with IBS as well as treatment options, and provide readers with a comprehensive review of the epidemiology, prevalence, management, and economic impact of the disorder. (It should be noted that 3 of the 5 articles in this series deal with analyses focused on the effects of tegaserod. Given that alosetron administration is restricted, the applicability of additional cost analyses of alosetron-based intervention strategies may be limited. Tegaserod, however, is not restricted and actually has several indications for its use, so analyses of the economic effects of this medicine may be important in steering formulary decisions or benefit coverage.) In one of these studies, a budget-impact model was developed to assess the economic effect of adding tegaserod to the formulary of a managed care organization.[36] This model estimated the economic impact for patients with IBS both 6 months before and 6 months after the initiation of tegaserod therapy. It was found that the total per-patient budget impact for all resources (including the cost of tegaserod) for a 6-month period was approximately $274 for women with IBS. Overall, 29% of the cost of tegaserod was offset by decreases in resource utilization (including pharmacy, inpatient, outpatient, endoscopic, and nonendoscopic resources). These results suggest that effective therapy can indeed decrease GI-related resource utilization, perhaps ultimately leading to a significant cost-offset percentage.

Also included in this issue of the journal was a retrospective, longitudinal study that evaluated the GI-related resource utilization (office visits, hospitalizations, emergency department visits, endoscopic and nonendoscopic procedures) in a managed care population consisting of tegaserod users and nonusers.[37] It was found that GI resource utilization by tegaserod users for all comparisons before and after the initiation of therapy showed significant decrements in all utilization categories except for GI drug prescriptions. Matched nonusers did not show consistent decrements in GI resource utilization. Last, in an effort to illustrate the indirect costs associated with IBS and the potential cost savings that might accrue after effective therapeutic intervention, an economic model was designed to assess the indirect costs associated with tegaserod therapy in female patients with IBS.[38] This model demonstrated that treatment resulted in gains of $1882 through avoided productivity losses per employee. The benefits of decreased amounts of work loss and the cost of therapy in this model predicted a very favorable benefit/cost ratio of 3.75, demonstrating the potential extrapolated value of effective therapy.

Conclusion
The symptoms of IBS and the impact of this chronic disorder on both patients and the healthcare system alike are substantial. Because IBS has such a high prevalence and predominantly affects adults of working age, it imposes a significant burden on the patient as well as the employer, third-party payers, and society through a variety of direct and indirect costs. Although estimates of the degree of this burden vary and may be difficult to ascertain or even recognize, it appears that the indirect costs associated with IBS (upwards of $20 billion annually) comprise the major component of total costs associated with the condition.

Strategies to reduce direct costs will necessarily be directed at recognition of the disorder and should include physician and patient education, paramedical-based education and therapy, lay support groups, optimization of the diagnostic approach to patients with suspected IBS, and implementation of IBS educational awareness and incentive programs similar to initiatives targeting other chronic disorders such as GERD, diabetes mellitus, and hypertension.[35,40] Additionally, there is emerging evidence that continued development and increasing use of clinically effective therapies that target the multiple symptoms of IBS appear to have the potential to facilitate significant reductions in both direct and indirect costs associated with this chronic disorder.

Funding Information

Supported by an independent educational grant from Novartis.

Brooks Cash, MD, FACP , Assistant Professor of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland; Chief, Gastroenterology Division and Colon Cancer Center Initiative, National Naval Medical Center, Bethesda, Maryland

Disclosure: Brooks Cash, MD, FACP, has disclosed that he has served as an advisor or consultant to Novartis and Wyeth.

Medscape Gastroenterology. 2005;7(1) �2005 Medscape

http://www.medscape.com/viewarticle/506873_1

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From Alimentary Pharmacology & Therapeutics

Irritable Bowel Syndrome in the United States: Prevalence, Symptom Patterns and Impact

A. P. S. Hungin; L. Chang; G. R. Locke; E. H. Dennis; V. Barghout

Summary and Introduction
Summary
Background: The impact of irritable bowel syndrome, a gastrointestinal motility disorder, is underestimated and poorly quantified, as clinicians may see only a minority of sufferers.
Aim: To determine the prevalence, symptom patterns and impact of irritable bowel syndrome in the US.
Methods: This two-phase community survey used quota sampling and random-digit telephone dialling (screening interview) to identify individuals with medically diagnosed irritable bowel syndrome or individuals not formally diagnosed, but fulfilling irritable bowel syndrome diagnostic criteria (Manning, Rome I or II). Information on irritable bowel syndrome symptoms, general health status, lifestyle and impact of symptoms on individuals' lives was collected using in-depth follow-up interviews. Data were also collected for healthy controls identified in the screening interviews.
Results: The total prevalence of irritable bowel syndrome in 5009 screening interviews was 14.1% (medically diagnosed: 3.3%; undiagnosed, but meeting irritable bowel syndrome criteria: 10.8%). Abdominal pain/discomfort was the most common symptom prompting consultation. Most sufferers (74% medically diagnosed; 63% undiagnosed) reported alternating constipation and diarrhoea. Previously diagnosed gastrointestinal disorders occurred more often in sufferers than non-sufferers. Irritable bowel syndrome sufferers had more days off work (6.4 vs. 3.0) and days in bed, and reduced activities to a greater extent than non-sufferers.
Conclusions: Most (76.6%) irritable bowel syndrome sufferers in the US are undiagnosed. Irritable bowel syndrome has a substantial impact on sufferers' well-being and health, with considerable socioeconomic consequences.

Introduction
Irritable bowel syndrome (IBS) is a chronic, episodic functional gastrointestinal (GI) disorder characterized by abdominal pain/discomfort and altered bowel habit (constipation, diarrhoea or alternating periods of both).[1] Patients often experience additional symptoms such as bloating, sensation of incomplete evacuation, straining (constipation) and urgency (diarrhoea). IBS patients can experience symptoms for many years, with an average duration of 10 or more years.[1,2] IBS is often unrecognized or untreated, with as few as 25% of IBS sufferers seeking professional health care.[3] Those seeking care are often frustrated by the lack of effectiveness of traditional treatment and management strategies.[4]

IBS prevalence is estimated to be 10-15% in Western countries.[5-9] Prevalence data and information on the health care-seeking behaviour of IBS sufferers have mostly been derived from independent studies using different methodologies and different diagnostic criteria. As there are no IBS-specific biological markers to aid diagnosis, doctors generally rely on symptom-based criteria. At least three sets of diagnostic criteria have been developed, including the Manning,[10] Rome I[11] and Rome II criteria.[12] The Rome I and II criteria are more refined than the Manning criteria, and include symptom duration within their definitions. Variations in study design, particularly the criteria used to diagnose IBS, affect the ability to compare or summarize data from multiple studies.[13]

One challenge of population-based IBS studies is ensuring that IBS is accurately diagnosed using specific, validated criteria, rather than the clinical judgement of health care professionals.[7]

IBS places a significant financial burden on society. Symptoms can significantly impact on the quality of life of sufferers, with considerable socioeconomic consequences.[14-18] For example, absenteeism from work is more prevalent in individuals with IBS than in those without,[1,19] and employers in the United States (US) are estimated to pay, on average, $1251 more for individuals with IBS than matched control beneficiaries over a 1-year period ( P < 0.001).[20]

A recent European study investigated the prevalence, symptom pattern and impact of IBS across eight countries in an attempt to define the magnitude of the problem facing health care providers.[21] The present study, which used the same methodology, evaluated IBS prevalence, symptom pattern and impact on work, social activities and well-being of sufferers in the US. Attitudes towards the health and consultation behaviour of IBS sufferers were also assessed.

Materials and Methods
Survey Methodology
A random-digit dialling technique as described previously[21] was used to identify study participants. This technique has proven feasibility and accuracy in health research[22-24] and enhances the representativeness of the study. Random-digit dialling allowed large numbers of people in the US to be easily identified while avoiding the possibility of cluster sampling often seen with multiple fixed-site surveys. Sampling limitations often noted with postal surveys were also avoided. Research supports this technique as a highly efficient way of yielding accurate data.[22-24]

This methodology assumed that more than 90% of the US households had a telephone and that approximately 25% of numbers were unlisted. Random-digit dialling sampling enabled numbers in the US to be assigned with a probability of selection. As previously described,[21] a random initial sample was drawn from all known listings using a 1 in n sampling interval and an algorithm was then utilized to randomize the last two digits, thus ensuring the inclusion of unlisted numbers. All telephone numbers were prescreened for a valid dialling tone to maximize data efficiency. All fieldwork was conducted on weekday evenings and weekends so that the working population was represented in the study. In order to enhance representativeness, quota sampling was applied in terms of age and gender. This survey was carried out by The Sample Surveys Research Group (now Synovate), West Malling, UK, and commissioned by Novartis Pharmaceuticals, New Jersey, US.

Development and Application of the Questionnaires
The survey included two questionnaires and was executed in two phases; the development of the original questionnaires has been previously described.[21] The first questionnaire was subjected to five stages of piloting and testing, including respondent validation. Further validation was conducted using clinicians and lay individuals in the US - terminology modification ensured respondent comprehension. The revised US version was piloted amongst 'live' respondents prior to commencement of fieldwork. The locally derived and adapted questionnaire was then tested in the US using the telephone interview technique.

In the first phase, a screening questionnaire was employed to identify subjects already diagnosed with IBS (medically diagnosed by their clinician) and to elicit information that identified non-diagnosed IBS sufferers according to the Manning, Rome I or Rome II diagnostic criteria. Subjects were classified as having undiagnosed IBS if they confirmed that they suffered from at least two of the Manning criteria and experienced abdominal pain/discomfort at least once in every 2 months in the previous 12 months. The screening questionnaire was presented to potential participants as being part of a general health project in order to avoid introducing bias and directing responses towards IBS or other GI conditions.

Patients were defined as having IBS with constipation (IBS-C) if they experienced one or more of the following: harder/more lumpy stools than usual, the need to pass stools less often than usual (<3 times/week), or periods of straining, which was not accompanied by the need to pass stools more often than usual (>3 times/day), looser/more watery stools than usual and periods of urgency. Patients were defined as having IBS with diarrhoea (IBS-D) if they experienced one or more of the following: looser/more watery stools than usual, the need to pass stools more often than usual (>3 times/day), or periods of urgency, which were not accompanied by the need to pass stools less often than usual (<3 times/week), harder/more lumpy stools than usual and periods of straining. Patients with other bowel habit patterns were defined as having alternating IBS (IBS-A). Differentiation into these specific IBS subtypes was based only on the symptoms suffered by each respondent, without reference to a specific time frame.

In the second phase of the survey, respondents who were identified as having IBS in phase I of the survey, either medically diagnosed or diagnosed using IBS criteria (Manning, Rome I or Rome II), were invited to participate in a more formal interview regarding their symptoms, general health factors, lifestyle and impact of IBS symptoms on their lives. Data on comorbid conditions, therapy/medication use and consultation patterns were also collected. Thus, three groups of respondents were identified: those with medically diagnosed IBS; those who had IBS that had not been medically diagnosed, but who fulfilled IBS diagnostic criteria; and a healthy comparator group identified from the screening questionnaire as not having IBS. Any individuals who had experienced IBS symptoms within the previous 12-month period were identified as current IBS sufferers.

For symptoms of constipation or diarrhoea, individuals were questioned (based onthe IBS diagnostic criteria) about: any periods needing to pass stools more often than usual (>3 times/day) or less often than usual (<3 times/week); any periods when stools were looser/more watery than usual or harder/more lumpy than usual; periods of straining when going to pass a stool; periods of urgency when going to pass a stool; feeling of incomplete evacuation after passing a stool; periods of bloating.

As in the European study,[21] the development of the questionnaire used in the US population incorporated the clinical experience of the clinicians involved with this study. Alternative diagnoses (not IBS) were excluded at an early stage of the questionnaire and pilot research was performed to ensure the Manning and Rome I/II criteria were effective in this setting. The questionnaire was designed and carefully validated to avoid order effects, such as suggestion based on earlier questions.

Based on the assumption of a conservative IBS prevalence rate of 5-10%, it was estimated that 5000 respondents would need to be contacted to reach 250-500 IBS sufferers in the US. Specific target age groups for the population were 18-34, 35-54 and over 55 years, with equal numbers contacted within these age groups.

Subjects
The study was carried out in the US in a sample of subjects aged 18 years or over. Those previously diagnosed with Crohn's disease, ulcerative colitis, coeliac disease, diverticulitis, peptic ulcer or cancer (including colon and gynaecological cancers) were excluded from the results because of possible overlap with IBS symptoms.

Results
From approximately 14 000 initial telephone contacts, a total of 5009 screening interviews were conducted; all questions in this section were related to general health. Among these, 708 individuals were identified as having current IBS (any diagnostic criteria) and, from this group, 318 individuals participated in the second phase of the questionnaire (366 individuals either did not want to take part in the second phase of the questionnaire or did agree but were not available when contacted).

Prevalence, Characteristics and Symptom Patterns of IBS (Medically Diagnosed and Not Medically Diagnosed)
Overall 708 individuals (14.1% of total screened) were identified as having current IBS [medically diagnosed ( n = 166; 3.3%) or met any diagnostic criteria (not medically diagnosed; n = 542; 10.8%)]. Results from this questionnaire are shown in Table 1 .

In general, medically diagnosed IBS patients reported a greater prevalence of individual IBS symptoms. The Manning criteria identified all current IBS sufferers (100%); the Rome I criteria identified 73% and the Rome II criteria identified 62%. Thus, only partial overlap of the IBS diagnosis was seen across these diagnostic criteria. The Rome II criteria appeared to be the most restrictive set. Of those individuals who had been medically diagnosed with IBS, 4% were deemed to have IBS-C compared with 21% with IBS-D. In those not medically diagnosed, these percentages were 15% and 21%, respectively. Most individuals with IBS (74% of those medically diagnosed and 63% not medically diagnosed) reported alternating symptoms of constipation and diarrhoea (IBS-A). When IBS sufferers were asked to categorize themselves according to these three subgroups, only approximately one-third of individuals medically diagnosed and not medically diagnosed with IBS defined themselves as having IBS-A (33% and 27%, respectively) compared with IBS-C (17% and 30%, respectively) and IBS-D (45% and 29%, respectively).

Age/Sex Distribution of Current IBS Sufferers (Medically Diagnosed and Not Medically Diagnosed)
Overall, the peak ages for current IBS symptoms were between 25 and 54 years (67.3% of IBS total; Table 1 ). IBS was more common in women than men (64% vs. 36%, respectively), particularly among those who had been medically diagnosed with IBS (81.3% vs. 18.7%, respectively). The highest prevalence of IBS was seen in working women, with a prevalence of 21% (5% medically diagnosed, 16% not medically diagnosed).

Comorbid Conditions
Current IBS sufferers (both medically diagnosed and not medically diagnosed) were more likely to have suffered from other GI disorders of function (previously diagnosed by a doctor) compared with non-IBS sufferers. IBS sufferers were twice as likely to suffer from gastro-oesophageal reflux disease (GERD; 22% vs. 10%, P < 0.001) compared with non-IBS sufferers.

Duration and Patterns of Symptoms
Results of the second phase of this study confirmed that IBS is a chronic disorder, with 16% of current IBS sufferers being medically diagnosed with the condition in the previous 12-month period, 8% in the previous 13-24 months, 26% in the previous 2-5 years and 14% 6-10 years ago. Overall, one-third of current IBS sufferers had had IBS for more than 10 years.

Although respondents had IBS for considerable periods of time, IBS symptoms remained fairly constant over time with 73% of medically diagnosed IBS sufferers reporting that their symptoms had never changed. Only 22% of current IBS sufferers reported some degree of symptom improvement since the screening interview. Current IBS sufferers typically experienced symptoms for an average of 8.1 days/month and reported a wide range of symptoms, with abdominal pain/discomfort being the most commonly reported (90%; Figure 1). The majority (71%) described their overall IBS symptoms as fairly or very painful. On each day with current symptoms (designated as a 'suffering day'), respondents with IBS had an average of 2.4 episodes of IBS. These episodes varied in duration but more than half (52%) of current sufferers experienced episodes more than 60 min in duration. More than half (64%) of individuals with current IBS symptoms believed that an episode of IBS was triggered by a certain food or drink while 30% cited stress as the trigger.

There appeared to be a gender difference in the reporting of IBS-related symptoms in current IBS sufferers. Women were more likely to report constipation, bloating, trapped wind, swollen tummy, tightness of clothing and tiredness. There were no differences in prevalence of abdominal pain, diarrhoea and heartburn between men and women with IBS.

Impact of IBS on Work, Lifestyle and Health
Responses from current IBS sufferers (medically diagnosed and not medically diagnosed) indicate that IBS negatively impacted upon a wide range of daily activities. Work productivity, particularly the ability to concentrate, and time management, was significantly affected in respondents with IBS compared with individuals without IBS (Figure 2; P = 0.01). The proportion of men and women reporting an impact was not significantly different.

In the 12 months prior to the survey, IBS sufferers had more time off work, spent more days in bed and cut down on usual activities on more days compared with non-IBS sufferers. Nearly one-quarter of IBS respondents worked fewer hours, 11% missed work and 67% felt less productive when at work because of their symptoms. Two-thirds of current IBS sufferers had cut back on the number of overall activities during the previous 12-month period for an average of 15 days. The average number of days affected by ill health leading to absenteeism was 6.4 vs. 3.0 days (current IBS sufferers vs. non-IBS sufferers). Overall, current IBS sufferers were twice as likely to spend at least 1 day in bed or cut back on usual activities compared with non-IBS sufferers. Nearly one-quarter of current IBS sufferers had missed social engagements.

IBS symptoms also had a significant impact on social well-being and daily social activities among sufferers compared with non-sufferers ( P = 0.01). Undertaking long journeys, going out for a meal and going on holiday were all noted as more of a problem for IBS sufferers than controls (Figure 3a; P = 0.01). In addition, diet and food choice were also adversely affected by current IBS symptoms (Figure 3b; P = 0.01 vs. individuals without IBS). IBS sufferers reported a wide range of effects of symptoms on daily life (>/=5 points on a scale of 0 = no impact to 10 = significant impact), in particular many felt they had to be either near a toilet or make frequent trips to the toilet (Figure 4). Again, the proportion of men and women reporting an impact was not significantly different.

Current IBS sufferers were more likely to perceive themselves as having poor health; compared with 54% of non-IBS sufferers, only 35% of IBS sufferers described themselves as having good health. More than half (57%) of all current IBS sufferers questioned felt that they would have more control over their life without IBS symptoms. An impact of health on relationships was also more evident amongst current IBS sufferers compared with non-IBS sufferers: more IBS sufferers found it difficult to make new friends (46% vs. 40%, P < 0.001) and have physical relationships (52% vs. 41%, P < 0.001), and they felt that their IBS symptoms affected family relationships (48% vs. 40%, P < 0.001).

Attitudes to Condition

In general, the attitude towards health and overall quality of life appeared to be affected to a greater extent in medically diagnosed patients than in IBS sufferers who were not medically diagnosed ( Table 2 ).

Current IBS sufferers commonly informed their partner about their condition (68%). Although they also often told other family members (56%) and friends (54%), they were less likely to inform colleagues (22%) or their employer (16%). Most confidants were deemed to be very (44%) or fairly (39%) understanding. Overall, one-quarter of IBS sufferers highlighted that their self-confidence was reduced as a result of IBS; this was particularly evident among the medically diagnosed group (46% vs. 17% of those not medically diagnosed). The majority (87%) of respondents medically diagnosed with IBS believed their IBS to be a real medical condition, compared with only 43% of individuals not medically diagnosed ( Table 2 ). As an indication of desire for effective therapy, nearly half of current IBS sufferers (46%) agreed that they would try 'anything' to alleviate their IBS symptoms.

Consultation Pattern and Health Care Use
A primary care doctor was the most common health professional seen by current IBS sufferers (83%); gastroenterologists were the next most commonly consulted group (40%; Table 2 ). Abdominal pain/discomfort was the most common reason for consulting a health professional (28% of consultations), followed by symptom frequency (10%). Current IBS sufferers had seen a doctor or nurse an average of 4.2 times in the past 12 months if medically diagnosed or 1.3 times if not medically diagnosed. More than half (53%) of respondents not medically diagnosed had seen a health professional at some time for their condition. In patients medically diagnosed with IBS, 25% had visited a health professional five or more times before their IBS diagnosis.

Medication Used
More than half (58%) of the current IBS sufferers who had visited their health professional had been prescribed medication and a similar number (57%) received dietary and lifestyle advice ( Table 2 ). The main medications taken were antacid and acid suppression therapy (25%), antidiarrhoeals (22%) and laxatives (11%); the serotonergic agents, tegaserod and alosetron, were not available at the time of the study. Antidepressant/anti-anxiety medication was taken by 1% of participants (5% in the medically diagnosed group and 0% in those not medically diagnosed). Most IBS sufferers regularly used over-the-counter medication (60%) and 47% had altered their diet in an attempt to alleviate their IBS symptoms. Treatments were deemed ineffective for a number of symptoms including constipation (41%), bloating (34%) and trapped wind (31%). Treatments for abdominal pain/discomfort were considered to be fairly effective in 53% of sufferers, although 18% considered them to be not at all effective.

Discussion
This study confirms the high prevalence of IBS in the US population and its impact on the working life, social activities and well-being of sufferers. The overall prevalence of IBS in this population was 14.1%, with only 3.3% being medically diagnosed. This compares with a prevalence rate of 11.5% in a previous European study,[21] and is consistent with other large US-based epidemiological studies, where prevalence estimates cluster around 10-15%.[25,26] Expected variations in diagnostic rates according to Manning, Rome I and Rome II criteria were seen, as previously noted.[21,27,28] Clearly, IBS prevalence can vary substantially depending on the diagnostic criteria employed.[29] This comprehensive, representative survey used specific, validated IBS diagnostic criteria to estimate prevalence and symptom patterns, and also assessed impact of IBS on work, lifestyle and health. In this study, prevalence rates were highest among those aged 25-54 years, and the prevalence of IBS among women was approximately two times higher than that recorded for men in individuals medically or not medically diagnosed with IBS. These findings corroborate previously published reports, which demonstrated a higher IBS prevalence in women than in men.[30,31] In patients medically diagnosed with IBS, 25% had visited a health professional at least five times before being formally diagnosed, suggesting that diagnostic criteria are not being properly utilized, IBS symptoms are not always recognized or are misdiagnosed, and/or that the diagnosis of IBS is not being communicated to the patient.

This US population study adopted a survey methodology similar to that used in a recent European study of IBS prevalence and impact.[21] That study comprised approximately 5000 respondents from each of eight countries with a total sample population of 41 984, whereas in the US, the total sample population was 5000. Thus, comparisons between the two studies remain limited. The only other US study using random-digit dialling to assess IBS included 1014 adult women with IBS.[28,32]

The clinical presentation of IBS is quite varied,[33] with sufferers in the present study reporting a wide range of symptoms. IBS sufferers also reported that their symptoms rarely improve and were fairly or very painful, as highlighted in previous studies.[2,34] In this study, the prevalence of individual IBS symptoms was higher in medically diagnosed IBS patients than in current IBS sufferers who were not medically diagnosed. This finding may be related to IBS severity, which is likely to be greater in patients presenting for treatment. Medically diagnosed patients may also have a greater awareness of IBS and its associated symptoms. Data confirmed that IBS is a long-term condition, with one-third of IBS sufferers having experienced IBS symptoms for over 10 years, a figure comparable with that in Europe (40%).[21]

It is well documented that IBS can have a considerable impact on sufferers' lives,[16,21,26,35-37] and this is compounded by the condition's chronic and episodic nature. This study reinforces that IBS has a substantial impact on quality of life. There was a large impact on absenteeism and work productivity, confirming previous findings in both US[1,2,20,34] and European[21] populations. Additionally, ill health was recorded for an average of 6.4 days in current IBS sufferers, compared with 3.0 days in non-IBS sufferers. One in six current IBS sufferers in the US had changed their work schedule and one in four had worked fewer hours. These data support findings from Drossman et al., [26] who reported that IBS patients missed three times more days from work than non-sufferers. Time management, the ability to concentrate and commuting time were also negatively affected in IBS sufferers in the present study. Regular social activities such as going out for a meal, long journeys or holidays were also hindered. Thus, the symptoms of IBS appear to affect the ability to live a normal life. This is further compounded by the fact that other functional GI disorders often coexist with IBS.[38] Although this was not fully assessed in this study, 24% of IBS sufferers had also suffered from GERD or dyspepsia.

Substantial health care use because of IBS was recorded in this US population. Sufferers used a wide range of medications for relief of IBS symptoms. Medically diagnosed IBS patients with current symptoms appeared to take fewer antisecretory medications and laxatives than those not medically diagnosed, presumably due to the availability of these medications over the counter. This finding contradicts data from Shih et al., [39] who reported that 89% of doctor visits generated prescriptions. At the time of the present study, treatment options for abdominal pain/discomfort, bloating and constipation were only viewed as being completely effective in a small proportion of users. As IBS symptoms are intermittent, treatment was often restricted to times when patients experienced symptoms.

A varying perception of IBS-A was highlighted in this study. Most IBS sufferers (74% medically diagnosed, 63% not medically diagnosed) had alternating symptoms of constipation and diarrhoea as defined by doctors and diagnostic criteria. However, when sufferers were asked to categorize themselves, only approximately one-third of medically and not medically diagnosed respondents with IBS defined themselves as having IBS-A (33% and 27%, respectively) compared with IBS-C (17% and 30%, respectively) and IBS-D (45% and 29%, respectively). This finding is in contrast to other published data, which reported equal prevalence rates of IBS-C, IBS-D and IBS-A.[25,34] A possible explanation for this discrepancy is the use of more strict criteria for IBS-A in the current study than in the Rome II subclassification.

In conclusion, IBS is a prevalent disorder that significantly impacts work, lifestyle and social well-being. Diagnosing and managing IBS can be challenging due to the lack of a diagnostic marker and effective treatment options. Individuals with IBS who are not formally diagnosed reported a significant prevalence of GI symptoms, which impacted on their work and other daily activities, although in some instances to a lesser degree than medically diagnosed individuals. All IBS sufferers face the challenge of their condition on a daily basis and this study highlights the huge unmet therapeutic need in IBS.

Aliment Pharmacol Ther. 2005; 21 (11): 1365-1375. �2005 Blackwell Publishing

A. P. S. Hungin ,* L. Chang ,� G. R. Locke ,� E. H. Dennis ,� V. Barghout �

*Centre for Integrated Health Care Research, Wolfson Research Institute, University of Durham, Stockton-on-Tees, UK

�UCLA, Los Angeles, CA

�Mayo Clinic College of Medicine, Rochester, NY

�Novartis Pharmaceuticals Corp., East Hanover, NJ

Aliment Pharmacol Ther. 2005; 21 (11): 1365-1375. �2005 Blackwell Publishing

http://www.medscape.com/viewarticle/506173_1

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Heather is the Administrator of the IBS Message Boards. She is the author of Eating for IBS and The First Year: IBS, and the CEO of Heather's Tummy Care. Join her IBS Newsletter. Meet Heather on Facebook!

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