When your doctor uses the term natural history, he or she is talking about how a disease will progress if it goes untreated. Most people are familiar with the natural history of common diseases. For example, they know that the average cold lasts 5 to 10 days, a typical viral flu that affects the intestinal tract may last 2 to 4 days, and high blood pressure left untreated will increase a person’s risk of a stroke or a heart attack. But what you may not know is that the natural history of disease is not the same in everyone. You may catch a cold with symptoms that last for weeks, whereas your husband feels better after only a few days. If you get migraine headaches, perhaps your symptoms go away after 2 to 3 hours. Other people with migraines are known to have symptoms for 12 to 36 hours.
Another term that doctors frequently use is prognosis, meaning the long-term outcome of a medical problem. The prognosis of a medical disorder depends on natural history and whether or not the disease evolves into other medical problems. For example, the prognosis of the common cold is excellent. Although a cold can be frustrating and annoying and produce symptoms that may make you feel crummy for a few days, the common cold never turns into another disease (although it may make you more susceptible to other diseases, such as pneumonia). Migraine headaches can certainly be debilitating, but no matter how frequently you get them, they will not increase your risk for a stroke or other life-threatening medical condition.
In contrast, long-standing type I diabetes (diabetes that must be treated with insulin) does not have as good a prognosis as the common cold. If you have this type of diabetes, you are more likely to develop eye problems (such as retinopathy), kidney damage (nephropathy), and nerve injury to your hands and feet (peripheral neuropathy). Similarly, if you have chronically high cholesterol, you are at an increased risk of developing heart disease. If you have an untreated infection in your stomach (Helicobacter pylori), you have an increased risk of developing an ulcer in either your stomach or small intestine or even developing stomach cancer.
People who have irritable bowel syndrome frequently ask about the natural history and prognosis of the disease. How long does IBS last? Will IBS evolve into another disease? Does IBS increase my risk of developing other medical problems, especially cancer? In this chapter, I address the most common concerns about the natural history and prognosis of IBS. Keep in mind that the natural history and prognosis of a disease varies from person to person, as illustrated by the examples given above.
Although researchers working on different studies may address the same question—such as “What is the natural history of IBS?”—they may come up with different answers. Research results may vary because of differences among study populations, for example. Researchers may carefully screen participants to include only people who have IBS in a study, but types of IBS vary from person to person, as well as among study populations at different research centers. For instance one center may recruit people from the general community who have IBS. Many of these people would have mild IBS symptoms or have had IBS symptoms for only a short time. In contrast, some research studies recruit people who are hospitalized and have IBS. These people likely have severe IBS symptoms, because they have already tried some simple remedies at home, did not see their symptoms improve, and thus sought a physician’s advice. Finally, some IBS-related research studies only enroll people who have seen a gastroenterologist or been treated at a specialized clinic for IBS. These people typically have had severe symptoms for a longer period than people from the general community who have IBS, and they have usually tried different types of treatments without success.
When we do research to learn about the natural history of IBS, we need to keep in mind the potential differences among study populations. In addition, we should consider the answers to two separate questions. One, what is the natural history of a single episode or flare of IBS? Two, what is the long-term natural history of this disorder over the course of several years or over the course of a person’s lifetime?
For the most part, the natural history of a single episode (called a “flare”) of IBS depends on the person and whether she or he suffers from IBS with constipation or IBS with diarrhea. Some people find that a flare of IBS may last 3 to 5 days and then resolve by itself or with the use of medications. For other people, flares may last weeks or, rarely, even months. Many people who have IBS track their symptoms during the course of months or years to see if there is a pattern to their flares. As discussed in Part III, tracking these episodes using a diary or calendar can be helpful, because it allows you to identify the precipitating event or events that may have caused the flare. Just like people who have migraine headaches or episodes of arthritis, people who have IBS have flares that last for a specific period, with fairly reproducible and consistent symptoms. The predictability of the flares is reassuring for many people who have IBS, because it helps them learn coping strategies.
IBS is a chronic disorder for most people. In one study, researchers found that during the course of two years, nearly 70 percent of people who had IBS continued to have some symptoms. The results of this study do not mean that 70 percent of people had daily, persistent symptoms during the 2-year period, but rather that they still had some symptoms at the end of the study period that classified them as having IBS. This research study was performed at an academic medical center, however, and people who have IBS and are referred to academic medical or research centers for evaluation and treatment are likely to have more intense or persistent symptoms than people in the general community who have IBS.
Other researchers have measured the persistence of IBS symptoms in people during a two-year follow-up period and even a five-year follow-up period. Although their study populations were not large, researchers from both studies found that approximately 66 percent of people continued to have IBS symptoms during the follow-up periods. These data only apply to people who have IBS, see a doctor, and then enroll in a research study. As discussed in Chapter 4, nearly one in seven adult Americans have some symptoms of IBS, but most of them (approximately 70 percent) never see a doctor for their problems. Unfortunately, we have little information about the natural history of IBS in this large group of people from the community who never seek medical advice. People who have IBS but avoid the doctor’s office may have mild symptoms that resolve on their own after several months or years. Thus, although a seemingly discouraging percentage of people have persistent symptoms of IBS, the data from the studies described above may not accurately reflect the entire population of people who have IBS.
People who have persistent symptoms of IBS often worry about whether IBS will transform into other medical problems. Whereas some people’s symptoms resolve completely over time, other people who have IBS may have their symptoms go away just as other, new symptoms appear. For example, people who have IBS may experience relief from their lower abdominal pain only to develop new symptoms of recurrent upper abdominal pain or discomfort. Chronic symptoms of upper abdominal pain or discomfort (often associated with eating a meal) are characteristics of dyspepsia, which frequently goes hand-in-hand with IBS (see Chapter 9 for more information). The appearance of new symptoms, however, does not indicate that IBS has changed into another medical disorder.
Fortunately, there is only good news for people who have IBS and are worried about their prognosis. There are absolutely no data in the medical or scientific literature to show that having IBS increases the risk of developing another medical disorder. IBS does not increase the risk of developing cancer of the colon or rectum. In fact, there is no evidence to suggest that having IBS increases the risk of developing cancer anywhere in the body. There are also no data to suggest that having IBS shortens a person’s lifespan or that IBS can transform into another disorder, such as inflammatory bowel disease (Crohn’s disease or ulcerative colitis; see Chapter 12).
Although many people who have IBS have symptoms that can last for months or even years, everyone experiences symptoms differently: some people’s symptoms resolve completely; others have symptoms that resolve while other, new problems develop; and some have symptoms that do not resolve completely but become less intense or less frequent over time. Regardless of the length or severity of their symptoms, people who have IBS can be reassured in the knowledge that IBS does not increase their risk of developing another medical condition.
Having IBS does not keep anyone from developing other disorders, of course, and you and your doctor still need to work together to schedule the routine tests recommended for people your age. This includes routine screening for breast cancer (this may include regular breast examinations, mammograms, or even thermal imaging) and pap smears (for women), vaccinations, and colonoscopies (colon cancer screening needs to start at age 50 in the average-risk Caucasian individual and 45 in African Americans).
• For most people who have IBS and go to see a doctor, IBS is a chronic condition with persistent symptoms that may last for months or even years.
• Flares of IBS are different for each person, and most people who have IBS are familiar with their typical symptoms. For each person who has IBS, the nature and duration of symptoms are usually fairly consistent.
• The prognosis for IBS is excellent. IBS has never been shown to increase the risk of developing inflammatory bowel disease or colorectal cancer or to decrease a person’s lifespan.