Irritable Bowel Syndrome: Prevalence, Risk, and Unmet Needs

Mark Pimentel, MD: Prevalence of IBS [irritable bowel syndrome]. This is a big disease. I mentioned that in the introduction. What are we talking about? How many people have IBS? Ali?

Ali Rezaie, MD: The prevalence of IBS is significant. Globally, it’s about 11%. That amasses to about 1 billion people in the world, and about 30 to 40 million people in the United States. So it’s a very common disease, and it is affecting a lot of people. It’s important to address how we treat these patients and how we help them, so they can go on with their lives, with their professional lives and social lives, because it’s affecting those things significantly.

Mark Pimentel, MD: I’m going to get on my high horse, because IBD [inflammatory bowel disease] gets a ton of funding. It’s a 1-million-person disease. IBS gets hardly any funding, and it’s a 1-billion-person disease, or at least 45 million in the US. And probably, its economic burden is much greater. What’s the disparity here? Is it we who are doing something wrong? Is it that the disease isn’t respected? Because that affects patients and that affects the clinicians. If the disease isn’t respected, the clinicians don’t respect it, the patients don’t get respected, and it’s a funnel-down effect.

Brennan Spiegel, MD: This is an important and complex question. We probably all have our own perspectives on it. I think historically we haven’t had a really good handle on the pathophysiology of IBS. It’s been confusing. Is this a disorder of the mind? Is this a disorder of the body? Is this a brain disorder? As a result, there are lots of different perspectives and views, which you’d think would be perfect for research. But I think without having clear-cut pathophysiological models—which are changing, as we’ll talk about today—it’s been harder to justify research grants.

Whereas in IBD, some of the basic science has advanced so quickly, and there are so many treatments available. Not that there aren’t in IBS, by the way, which is a misconception, but the biological model of IBD has advanced to the point where it feels maybe more justifiable to put money into it. But you could argue the exact opposite—that we’ve sort of solved a lot of that. We haven’t cured IBD by any stretch, but IBS is further behind in funding, as you point out, and there’s definitely a disproportionate focus on this condition.

William D. Chey, MD: I think the other thing that is very important is that the perception by physicians, and I would say patients, is that IBD is a morbid disease that actually kills people, you know? It’s associated with cancer, or strictures, or a whole host of complications that are scary and impactful. IBS is really viewed as more of a lifestyle disease, which is really unfair given how much these patients suffer. I think that people tend to not necessarily equate the suffering with importance as opposed to if IBS, for example, was associated with a greater risk of cancer or some other fatal outcome. Then I think it would probably be viewed differently from how it is.

Brennan Spiegel, MD: Few people understand that the risk of suicide, for example—which we wrote a paper on—is not trivial among people with chronic abdominal pain. These are some of the often whispered secrets about functional abdominal pain in IBS. It can really profoundly affect people’s quality of life.

Mark Pimentel, MD: I agree with all that. The complicated part of all this is that in the mix of this pseudo chaos, the patient who’s suffering is being told, “Eh, it’s not going to kill you.” Then they’re somewhat dismissed by some clinicians. And so if we come to 1 point on this topic, don’t do that to your patients. Take them seriously, because they have a real disease.

But that leads me to risk factors. What are the risk factors that you think are important in IBS? We’re going to discuss this in more detail later, Tony, but maybe you can sort of get us a little up to speed on some of these things that are happening?

Anthony J. Lembo, MD: Sure. There are a number of different risk factors. We know that IBS, particularly IBS with constipation, is more common in women. It’s more equal for IBS with diarrhea between men and women. We also know that people who have had an infection have a higher risk of developing IBS. And we know that people who have underlying psychosocial factors, including anxiety, will have a higher risk of developing IBS. There have also been some data on socioeconomic status. The lower the status, maybe the higher the risk of having IBS-related symptoms.

Mark Pimentel, MD: Speaking of postinfectious, Dr Rezaie. Again, we’re going to get deeper into this, but just as a flyover, what’s going on there? What do we know? Or what are we starting to know in terms of postinfectious IBS?

Ali Rezaie, MD: That’s a fascinating concept in IBS. Whenever we pick up food poisoning or infectious gastroenteritis, especially with gram-negative bacilli, which are the usual bacteria that you hear in the news—Salmonella, Campylobacter Helicobacter, or E coli [Escherichia coli]—you develop that infectious gastroenteritis. But as that bacteria leave your body, you have roughly a 12% chance of developing IBS symptoms. This is called postinfectious irritable bowel syndrome.

Mark Pimentel, MD: So it’s literally a cause of IBS. Today we actually know more about the ultimate cause of at least a segment of IBS than we do of IBD. Nobody knows what started the IBD. There was no event. But in IBS, we have an event at least accounting for a portion of IBS. Let’s say 100 people show up in your office with dIBS [diarrhea-predominant irritable bowel syndrome]. What portion of those do you think—there are going to be varied opinions on this panel, but let’s start with Bill—are postinfectious, in your experience?

William D. Chey, MD: Of the D group?

Mark Pimentel, MD: Of the D group.

William D. Chey, MD: Probably somewhere between 10% and 20%, I would guess. I think there is a lot of debate as to what the right number is, because we don’t have great prospective data to really guide us that way.

Brennan Spiegel, MD: It’s hard to know because some people may recall a particular episode when they had traveler’s diarrhea or they got really sick, and then others may not really remember that but may have been exposed to the pathogen and maybe had some grumbling stomach. Yet they were still exposed, and that potentially could still be a trigger.

Mark Pimentel, MD: And that probably still complicates that. I’m going back to Bill. What are the unmet needs? And that’s very vague, but I think there’s a lot you could say here because there are so many unmet needs. But just give me your high-level opinion. What are we missing? What do we need to do?

William D. Chey, MD: I think this is really the question, right? The easy answer would be to say that there are more effective therapies. We do always need more effective therapies, but what we really need, in my opinion, to make the quantum leap in terms of solving this problem, is greater specificity in regard to the diagnosis. In other words, not only helping identify patients on the basis of symptoms but also using symptoms and then having biomarkers to help us to parse out patients on the basis of pathophysiology. Because that’s the way we’ll be able to choose the right treatment for the right patient, and go from 40% of patients getting better to 80% of patients getting better, right? That’s what we really want. So to me, that is the real unmet need.

Transcript edited for clarity.