The epidemiology of functional gastrointestinal disorders in North America.

This article has summarized the epidemiology of several disorders commonly seen in a gastroenterologist's practice. The emphasis has been on population-based data because many people with these disorders never seek health care, and psychological features have been shown to be strongly associated with health care-seeking behavior. Each of these disorders is common in the community; in fact, the majority of the population experiences intermittent gastrointestinal symptoms. In general, the national surveys sponsored by the U.S. Public Health Service have been shown to underestimate the prevalence of these conditions. In part, this is due to the fact that subjects are asked to report diagnoses rather than symptoms, and current coding schemes do not provide specific codes for each of the functional gastrointestinal disorders. Still, these studies have demonstrated the large number of physician visits and overall costs attributable to these disorders. A number of surveys of more limited populations have been done to assess the prevalence of these disorders. Rates have varied because of the definitions used and the degree to which organic diagnoses are excluded. These studies have been helpful in demonstrating the burden of illness in the community. Age and gender differences in the community have been much less marked than those identified in clinic-based studies, thus highlighting the importance of population-based research. Future studies need to focus on the incidence and natural history of these disorders. Studies of incidence cases can best evaluate the role of etiologic factors, whereas studies of prevalent cases are best for assessing the burden of disease in the community. Understanding the natural history of these disorders is important in determining the efficacy of future therapeutic interventions. The fact that these disorders represent 50% of visits to a gastroenterologist practice highlights the importance of these disorders and the potential contribution of gastrointestinal dysmotility in clinical practice.