Obstructive sleep apnoea (OSA) is associated with a variety of important complications, namely cardiovascular, neurocognitive and metabolic disturbances. The prevalence of OSA is well studied in children and adults. However, adolescence - an interface between childhood and adulthood, and a period of developmental changes known to affect sleep is largely unexplored in relation to OSA. The only published prevalence study on adolescents is limited by its small sample size, not a true representation of the general population and primarily focused on Caucasians. In this proposal, the investigators aim to determine the prevalence of OSA, and associated clinical features in a population-based sample of adolescents aged between 12 and 16 years. The sample selection will be based on a stratified (by districts) and clustered (subjects within randomly selected schools) randomised sampling frame. Each participant will fill in a sleep habit questionnaire, undergo anthropometric measurements, physical examination and complete home polysomnographic recordings. Participants will undergo Conners' Continuous Performance Test and have blood samples taken to phenotype their cardiovascular and metabolic risk. The primary outcome is prevalence of OSA, assessed by the obstructive apnoea hypopnoea index. Secondary outcomes include use of logistic regression models to assess association between different severities of OSA and various demographic, clinical and laboratory variables. The obtained result will provide the much-needed OSA prevalence in adolescents which is essential for estimating the true burden of disease within this population. This information is also vital when considering population-based health policies and interventional strategies. Globally, the findings from currently evidence-sparse region of the world allow future international comparison of disease burden. Our study will also form a platform from which repeated measurements can be made to assess time trends and to answer the important question of whether adulthood OSA takes its origin from adolescence.