To examine the prevalence of functional dyspepsia in the general population, and to evaluate the natural history/clinical course of patients with functional dyspepsia. Full-length published manuscripts during 1980-2002 were included if: (i) participants had uninvestigated or functional dyspepsia; (ii) dyspepsia was defined; (iii) for prevalence, population-based samples were evaluated; (iv) for prognosis, the total number of the inception cohort and the total number of individuals available at the end of follow-up were reported. Twenty-two studies (1976-2002) that examined the prevalence of dyspepsia fulfilled the inclusion and exclusion criteria; 17 studies examined more than 1000 participants, but only two studies provided information sufficient to calculate the prevalence of functional dyspepsia (11.5-14.7%). The prevalence of uninvestigated dyspepsia was in the range 10-40%. When the definition of dyspepsia was restricted to participants with upper abdominal pain, irrespective of the presence of heartburn or acid regurgitation, the prevalence rate estimate was 5-12%. Thirteen studies examined the clinical course of functional dyspepsia (seven retrospective and six prospective). Sample sizes were small (n = 35-209). A follow-up ascertainment of symptoms amongst individuals in the original cohorts was obtained in 92.5-98.2% of prospective studies and in 67.7-82.2% of retrospective studies. The follow-up duration was in the range 1.5-10 years for prospective studies and 5-27 years for retrospective studies; the median follow-up duration for all studies was approximately 5 years. A variable prognosis was reported. An outcome of symptom improvement or becoming asymptomatic was reported in at least one-half of patients in 10 of the 13 studies, and in at least two-thirds of patients in six of the 13 studies. Prognostic factors were inconsistent and, in general, poorly described. Functional dyspepsia is prevalent world-wide, but the prognosis remains poorly defined. There is a need for population-based studies to examine the prevalence and clinical course of documented functional dyspepsia.
