Chronotherapy (timed ingestion of medicine) for high blood pressure in patients with obstructive sleep apnoea (OSA)

Following screening, patients on Angiotensin Converting Enzyme Inhibitors (ACE-i) or Angiotensin Receptor Blockers (ARBs) will undertake a washout period of 3 weeks. All patients will then undergo a run-in period with perindopril 10mg (morning dose) to ensure medication tolerability. The run in period will be 1 week for those previously taking ACE-i, 2 weeks for those previously on ARBs, and 4 weeks for all patients. Patients will then be randomised to one of two anti-hypertensive treatment orders for 6 weeks and then cross over to the alternative order. The two treatment orders are. Treatment Order 1: Perindopril 10 mg morning dose and placebo bedtime dose Treatment Order 2: Placebo morning dose and Perindopril 10mg bedtime dose There is no washout period between the two treatment orders. Following completion of both treatment orders, patients will continue with their last allocated anti-hypertensive treatment order (1 or 2) and also receive Continous Positive Airway Pressure (CPAP) treatment in an open label design for 8 weeks. CPAP will be delivered via a nasal mask and the pressure will be individually titrated during an in-laboratory pressure determination study prior to commencement of 8 weeks CPAP therapy. The pressure will be titrated to a level that fully prevents apnoeas and hypopneas and normalizes breathing during sleep. During the 8 weeks of CPAP treatment, patients will be encouraged to use the device every night for the entire sleep period.