Assessment of PPIs use
At baseline, self-reported PPI use was firstly assessed from participants using a touchscreen questionnaire, and then confirmed during verbal interview with a trained staff. The recorded type of PPIs included omeprazole, lansoprazole pantoprazole, rabeprazole and esomeprazole. In this study, regular use of PPIs was defined as taking PPIs in most days of week for the last 4 weeks.