Inclusion Criteria

• Male or female
• Any race
• Age between 45 and 75 years
• Evidence of established coronary artery disease
  • Multi-vessel coronary artery bypass surgery (CABG) >1 year prior to ApneaLink™ assessment
  • Multi-vessel percutaneous angioplasty (PTCA) and/or stent equal to or greater than 90 days prior to ApneaLink™ assessment
  • Stable angina or unstable angina clinical event equal to or greater than 30 days and confirmatory test equal to or greater than 7 days prior to ApneaLink™ assessment
  • Defined as either
    • ≥70% diameter stenosis of at least one major epicardial artery segment
    • ≥50% diameter stenosis of the left main coronary artery
    • >50% stenosis in at least two major epicardial arteries
    • Positive stress test with ST depression equal to or greater than 2 mm or a positive nuclear perfusion scintigram
  • Previous MI equal to or greater than 90 days prior to ApneaLink™ assessment
• Evidence of cerebrovascular disease
  • Previous stroke includes definite or presumed cerebral ischaemia/infarction and intracerebral but not subarachnoid haemorrhage equal to or greater than 90 days prior to ApneaLink™ assessment 
  • Minor disabling stroke with minimal residual neurological disability and modified Rankin Score of '0 = no symptoms' or '1 = No significant disability despite symptoms, able to carry out all usual duties and activities' within 7 days of stroke onset at ≥7 days prior to ApneaLink™ assessment
  • Previous transient ischaemic event (TIA) of the brain or retina (symptoms <24 hours) but not of presumed vertebrobasilar system ischemia, and diagnosis must be confirmed by a suitably qualified clinician ≥7 days but <1year prior to ApneaLink™ assessment
• Moderate-severe OSA equivalent to apnea plus hypopneas index [AHI] >30 per hour of sleep as determined by a ≥ 4% oxygen dip rate > 12/ h on overnight testing using the ApneaLink™ device, and confirmed by the SAVE core lab in Adelaide upon receipt of the ApneaLink™ data
• Able and willing to give appropriate informed consent

Exclusion Criteria

• Any condition that in the opinion of the responsible physician or investigator makes the potential participant unsuitable for the study
  • Co-morbid disease with severe disability or likelihood of death
  • Significant memory, perceptual, or behavioural disorder
  • Neurological deficit (e.g. limb paresis) preventing self administration of the CPAP mask
  • Contraindication to CPAP use e.g. pneumothorax
  • Residence sufficiently remote from the clinic to preclude follow-up clinic visits
• Any planned coronary or carotid revascularisation procedure in the next 6 months
• Severe respiratory disease defined as
  • Severe chronic obstructive pulmonary disease (FEV1/FVC < 70% and FEV1 < 50% predicted)
  • Resting, awake SaO2 < 90% by ApneaLink™ device
• New York Heart Association (NYHA) categories III-IV of heart failure
• Other household member enrolled in SAVE trial or using CPAP
• Prior use of CPAP treatment for OSA
• Increased risk of a sleep-related accident and/or excessive daytime sleepiness, defined by any one of the following:
  • Driver occupation (eg truck, taxi)
  • 'Fall-asleep' accident or 'near miss' accident in previous 12 months
  • High (> 15) score on the Epworth Sleepiness Scale
• Severe nocturnal desaturation documented on the ApneaLink™ device as > 10% overnight recording time with arterial oxygen saturation of < 80%
• Cheyne-Stokes Respiration (CSResp)
  • CSResp identified on ApneaLink™ nasal pressure recording by typical crescendo-decrescendo pattern of respiration with associated apneas and/or hypopneas in the absence of inspiratory flow limitation
  • Exclusion if > 50% of nasal pressure - defined apneas and hypopneas judged to be due to CSResp