Inclusion Criteria:  - Subjects participants from the 2003 cohort  Exclusion Criteria:  Neuromuscular disease Pathological central apnoea Severe chronic lung disease with documented hypoxaemia or awake oxygen saturation <92% Chronic respiratory failure (unrelated to OSA) Acquired upper airway disease/obstruction Craniofacial abnormalities (e.g. secondary to trauma and malignancy)  Other arrangement:  Subjects who have any respiratory illness within 2 weeks of the scheduled follow-up visit will have their assessment re-arranged until they have fully recovered. Subjects taking medications that may affect sleep, upper airway patency or blood pressure (for example sedatives, stimulants, antihistamines, and cough medicine) within a week from recruitment will also be rescheduled to participate when they are free from medication use for at least 2 weeks. Subjects with hypertension and are on anti-hypertensive therapy are allowed to continue on their medication and the information will be obtained and recorded during data collection.