Fig. 1.

Flow chart of inclusion and exclusion of subjects. A total of 16,008 people who underwent a health inspection (gastroscopy, a self-report questionnaire, and a serum Helicobacter pylori IgG antibody test) at our center were investigated. Subjects younger than 17 years of age, subjects who underwent upper gastrointestinal (GI) surgery, subjects with adenoma or carcinoma in the upper GI tract, subjects who did not properly answer the questionnaire, subjects using proton pump inhibitors or histamine-2 receptor antagonists, and subjects previously diagnosed with functional dyspepsia were excluded from the study. If the results of the serum H. pylori IgG antibody test were equivocal and other H. pylori tests were not performed, subjects were excluded, because the presence of H. pylori infection could not be determined. Subjects without peptic ulcer disease (PUD) were categorized into the healthy control group. Among subjects diagnosed with PUD, subjects with ulcers in the scarring stage were excluded. The remaining subjects were categorized into the symptomatic or asymptomatic PUD group according to the presence of symptoms.