Our research team has established a polysomnography (PSG) quantified population-based paediatric sleep cohort in 2003 for a childhood OSA prevalence study. Subjects were recruited from 13 randomly selected primary schools. All subjects from this original cohort will be invited to join this 18-year follow-up study to repeat the following data collection: questionnaires, anthropometric measurement, sleep study, 24-hour ambulatory blood pressure (ABP) measurement, echocardiography and neurocognitive assessment.