Irritable bowel syndrome (IBS) is a chronic medical disorder characterized by abdominal pain, which is a sine qua non for diagnosis, and altered bowel function. These 2 components are needed to make a diagnosis of IBS. Clearly, it's more complicated than that but that's the essence of it.

There are a number of epidemiologic studies that have been done over the last 10 to 15 years across the globe looking at the true prevalence of IBS. And certainly there are both methodologic difficulties and differences between these studies, but as you go through this very busy map you can see that in North America, it's about 10% to 20% in the United States and Canada. It's similar, perhaps a little bit less, in Europe. As you move out to Asia, it is somewhat desperate, Australia being 12%, Singapore quite low, Japan and China being somewhat high, and South America and Africa being exceedingly high, at least based on the data coming from other countries.

It is hard to interpret some of these studies because there aren't many of them. Many of those numbers are based on one study and, clearly, additional research is needed to really determine the true worldwide prevalence. But it's safe to say we have somewhere between 10% and 20% incidence of IBS around the globe.

When one looks at who gets IBS, it's clearly a disease of young and middle-aged people. Once you get older than about 60 years of age, the incidence tends to fall. It is a disorder, in almost all countries, of females. It is much more common for women to report the symptoms consistent with IBS as opposed to men.

If you look at the prevalence of IBS compared with that of other chronic medical diseases, it is indeed a significant problem. It is either equal to or slightly higher than hypertension, a huge problem in this country. It is much more common than asthma, diabetes, and, although it is clearly less lethal, heart disease.

It is a stable diagnosis. Once someone is diagnosed with IBS, a number of studies done over the last 5 to 7 years have shown that people will not go on to be rediagnosed with another condition. If you use the Rome criteria, if you do prudent and appropriate work-up, the chance of misdiagnosing a patient with IBS is pretty slim and you can make this diagnosis with a high degree of confidence.

Having said that, once you make the diagnosis of IBS, IBS patients will see their physicians. They will see their physicians much more often than patients who do not have IBS. And if you look at patients who have gastrointestinal (GI) symptoms, it is also more significant, and when you tack that on to patients who have non-GI complaints, IBS makes up a huge percentage of the doctor visits, at least in this country.

If you look at visits to gastroenterologic specialists, inflammatory bowel disease (IBD) is the highest; somewhat not unexpectedly, because of the spectrum of problems that goes along with that complicated disorder.

But if you look at what we perceive as an extraordinarily common problem in GI, gastroesophageal reflux disease (GERD), you actually see many more IBS patients in your practices. And that creates a double dilemma because the treatment for this disease, at least traditionally, has been pretty well defined and we're just beginning to define the treatment of IBS, which is one of the reasons I think we tend to under-acknowledge these patients because, in the past, we've been unable to help them.

IBS represents about 12% of all patients seen in primary care practice, which to me is the more impressive number, and about 28% of patients in GI practices. In any form of office-based medical practice, this is an extremely common problem.

If you look at the orange bars going left to right, and you look at patients with IBS with constipation and compare them with the US population, and you look at the spectrum of IBS-like symptoms, you can see that the IBS patients are dramatically different. This is not a subtle alteration in bowel habits that can be easily overlapped with the usual cyclic changes we all have in our bowel patterns. This is a significantly different group of patients who have significantly more distress in a wide spectrum of bowel-related symptoms.

If you look at how patients rate the severity and intrusiveness of their symptoms and compare them with how physicians rate them, physicians tend to underestimate the difficulties associated with IBS with constipation and tend to slightly overrate, at least compared with patient reports, IBS with diarrhea. They see the diarrhea-predominant form of this illness as being more intrusive to patients, although patients would disagree. If you look at patients with alternating constipation and diarrhea, physicians see that by far as the most problematic form of the disorder, but patients don't see it that way at all. So we have a dichotomy between how we perceive this as physicians and how patients perceive it themselves. It's a significant issue that we need to address. We need to communicate better and help our patients understand their symptoms, as well as us understand them better.

This is Gralnek's wonderful and very provocative study that was published in Gastroenterology in 2000 looking at health-related quality of life in patients with a number of medical diseases, GI and non-GI, across the various domains of the Short Form with 36 questions (SF36), the standard quality of life measure we use. When compared with gastroesophageal reflux disease (GERD), diabetes, and normal controls, basically the baseline population, IBS by far had the lowest quality of life.

This is a condition that has a very low mortality but a very high morbidity, much of this morbidity being nonmedical. It's economic and social as well as medical.

Hahn's article, which is now a couple of years old, looked at patients and the impact of their disorder on their activities of daily living. The number of patients who missed work was 30%, patients who cut back on their productivity at work was close to half, 15% worked fewer hours,, and 12% changed to working at home. People completely removed themselves from the extramural workforce. People who lost their jobs was also 12%, 9% changed jobs because of their health reasons, and 8% changed the schedules of their activities of daily living in general.

So when you get this disorder, at least if you get it to any significant degree, it's clearly going to have a very negative impact on your life and how you live your life.

In a study done about 10 years ago by Drossman's group, patients with IBS lost about 13 1/2 days per year of work and school productivity, while for non-IBS controls, it was basically one third of that. These patients don't do well.

The cost of IBS has become a very difficult and very fluid field because traditionally we measured it in terms of work-up evaluation and cost of medical care. Clearly, that's an underrepresentation of the cost. So these days the studies are looking at direct costs, ie the medical costs associated with this disorder; the indirect costs in terms of reduced productivity and the use of over the counter (OTC) drugs; and the intangible costs, which is impaired quality of life, impaired social relationships, basically, how much joy does this disorder eliminate from of a patient's life?

It's pretty dismal.

When you look at patients who missed work days, lost productivity while at work, and were impaired at work with self-reported IBS, the cost sky rockets. It is clear that people are, in addition to losing pay and time at work, are also losing their confidence to participate effectively in society and in the workforce because of the symptoms generated by the disorder.

We don't know exactly what this disease costs. We probably never will completely. But the indirect costs seem to be bouncing around $20 billion, and the direct costs for medical care are between $1.7 and $10 billion depending on what study you use. A lot of variables go into that in terms of the cost of delivering a service in a given location. What that rounds out to is approximately $30 billion a year in the United States, which is a tremendous amount of money for what we've traditionally perceived as a trivial disorder.

These data come from a health maintenance organization (HMO) population where the costs are tracked very closely. IBS patients exceed the cost of care for non-IBS controls. The interesting thing is a high proportion of these costs is not for GI care. The IBS patients are higher utilizers of healthcare across the board, for even non-GI reasons.

IBS patients cost employers more to have in the workplace. They are folks who carry significant disability with them, and our job as physicians is to positively impact that and reduce that significant dilemma.

It is clear that patients with IBS have approximately twice as many surgeries as folks who do not have IBS. Hysterectomies, appendectomies, and cholecystectomies are all more common in patients with IBS, and the suffering, the cost, and the potential postoperative complications that go with that are something we need to move away from. The excess of cholecystectomy in IBS patients compared with non-IBS patients is particularly significant for reasons that remain unclear but probably because, as people get older with their irritable bowel, we move away from the appendix and toward the gall bladder.

To summarize the impact of IBS, it is a multispectral, multidimensional problem. We have a significant prevalence in this society and probably in most societies across the world. It clearly reduces quality of life. These patients are suffering and they're suffering in a very significant way.

IBS accounts for 12% in primary care practices and about one third of gastroenterology practices. It's something that we cannot ignore and we cannot not invest our research efforts in. The annual cost of the disease is high, and in the economic environment in medicine these days, it is not going to get any lower. We need to find a way to get these patients feeling better and to decrease their healthcare utilization.