The Effect of Continuous Positive Airway Therapy on the Blood Pressure in Sleepy vs Non-sleepy Patients With Obstructive Sleep Apnea

Obstructive sleep apnoea (OSA) is one of the most common noncommunicable types of disease, it affects about 1 billion people across the world. Left untreated, it causes apnoeas and hypopnoeas to fragment sleep, with frequent arousal from sleep and intermittent hypoxia associated with increased work of breathing. Frequently, it leads to excessive daytime sleepiness, as measured subjectively by the Epworth Sleepiness Scale, or, objectively, by the multiple sleep latency test (MSLT) or the maintenance of wakefulness test (MWT). OSA can lead to sustained high sympathetic tone at night, which in the long-term may impact on the cardiovascular risk. The investigators hypothesised that any primary airway therapeutic effect on the cardiovascular system, as measured by the blood pressure, in patients with OSA will differ dependent on whether subjects are excessively sleepy, or remain so when treated. Hypothesis 1. Office blood pressure (SBP, DBP) responses to CPAP in patients with OSA who are excessively sleepy (ESS\>10) at baseline vs non-sleepy patients at baseline. 2. 24-hour BP data (SBP, DBP, dipping, nocturnal and daytime) in sleepy patients in response to CPAP vs non-sleepy patients. 3. Adherence to treatment in sleepy patients may be different to non-sleepy patients and the observed effect effects will be adjusted in a secondary analysis according to available adherence data and follow up time.