Continuous Positive Airway Pressure Treatment of Obstructive Sleep Apnea to Prevent Cardiovascular Disease (SAVE)

• A composite of the CV endpoints of CV death, non-fatal acute myocardial infarction, non-fatal stroke, hospital admission for heart failure, and new hospitalisation for unstable angina or transient ischaemic attack. [ Time Frame: Reviewed 6-monthly; average patient follow up, 4 years ] [ Designated as safety issue: No ]
  

• Composite of CV death, MI & ischaemic stroke; components of primary composite endpoint; re-vascularisation procedures; all-cause death; new onset atrial fibrillation; new onset diabetes; OSA symptom scores; mood; health-related quality of life. [ Time Frame: Reviewed 6-monthly; average patient follow up, 4 years. ] [ Designated as safety issue: No ]
  
• In a sub-sample of 600 subjects pathophysiological mechanisms of CPAP-induced CV event reduction will be explored by assessing various intermediate markers of CV risk [ Time Frame: baseline and at 6-months, 2 and 4 years following randomisation ] [ Designated as safety issue: No ]
  
• Cardiac MRI to assess effects of CPAP on cardiac structure and function. [ Time Frame: Randomisation and at 6 months follow-up ] [ Designated as safety issue: No ]
  In a sub-sample of 200 participants (100 from the CPAP plus standard treatment and 100 from the standard treatment arms) the effect of CPAP on cardiac and vascular function using cardiac MRI will be investigated. The sub-study will evaluate left and right ventricular mass, volume and systolic/diastolic function and compliance of the aorta.
  
  

There is increasing evidence to indicate that OSA is an important modifiable risk factor for CV disease including stroke, MI, and heart failure. Increased nocturnal arterial blood pressure (BP), hypercoagulability, oxidative stress, inflammation, insulin resistance and cardiac arrhythmias are all associated with OSA. These effects are presumed to accelerate the progression of atheromatous disease, particularly within the coronary or cerebral vasculature. Moreover, OSA also appears to increase the risk of sudden death during sleep, which is different from the circadian pattern of sudden death in those without OSA, suggesting that episodes of apnea may have a direct triggering effect for cardiac arrhythmias or MI.

CPAP is now standard therapy for symptomatic OSA, with adherence to treatment comparable to that of other therapies for common chronic diseases. CPAP can eliminate apneas and improve daytime sleepiness, mood and quality of life. Furthermore, short term (1-3 months) randomised controlled trials of CPAP have shown modest reductions in blood pressure (BP) and other markers of CV disease, including C-reactive protein (CRP) and coagulation. However, the epidemiological data is complicated by potential residual confounding factors and the randomised evidence is limited. Thus, a direct causal link between OSA and CV disease remains inconclusive. The management of OSA, therefore, remains principally directed towards symptom control rather than CV risk modification.

The present trial aims to test whether long-term use of CPAP can reduce the incidence of CV events. If the trial shows that CPAP treatment of OSA reduces the incidence of CV events it will influence clinical practice toward the early detection and management of OSA, and add CPAP to the range of strategies available for the prevention of CV disease.