Hot Line Session Results: Hot Line prevention and lipids
Continuous positive airway pressure (CPAP) does not prevent cardiovascular events in patients with moderate-to-severe obstructive sleep apnea (OSA) and established CV disease, according to the population-based SAVE study. Presented as a Hot Line yesterday, the findings were published in the New England Journal of Medicine.
The results were not expected. ‘Given the level of risk of cardiovascular disease attributed to OSA in previous observational studies, we were surprised not to find a benefit from CPAP,’ said presenter Doug McEvoy, from the Adelaide Institute for Sleep Health, Australia.
OSA affects around 40-60% of patients with CVD and has been associated with increased risk of cardiovascular events. It is known to cause episodic hypoxaemia, nocturnal sympathetic activation and elevated blood pressure, and also to influence oxidative stress, inflammation and hypercoagulation. Furthermore, large negative intrathoracic pressure swings impose mechanical stress on the heart and great vessels.
CPAP has become the standard treatment for OSA. Observational studies have shown that CPAP use is associated with lower rates of CV complications and death, especially among patients who are adherent to treatment. However, randomised trial data is lacking for any benefit of OSA treatment for CVD prevention. The Sleep Apnea Cardiovascular Endpoints (SAVE) study was thus designed to explore whether treatment with CPAP does indeed reduce the incidence of future CV events among those with OSA.
Between December 2008 and November 2013, 2717 adults aged between 45 and 75 years with moderate-to-severe OSA and established coronary or cerebrovascular disease were randomised to receive CPAP treatment plus usual care (n=1359) or usual care alone (n=1358).
The patients, who were recruited from 89 clinical centres in seven countries, had a one week run-in with a sham CPAP mask prior to randomisation. They had to demonstrate effective use for a minimum of three hours a night. The investigators excluded those with severe sleepiness, very severe oxygen deprivation, advanced HF, and prior CPAP use. The primary endpoint was a composite of CV death, MI, stroke, hospitalisation for TIA, unstable angina or HF.
Results showed after a mean follow-up of 3.7 years that the primary endpoint occurred in 229 (17.0%) of the CPAP group and 207 (15.4%) of the usual-care group.
However, not all was disappointment. The study also showed that CPAP significantly improved patient well-being. It reduced snoring and daytime sleepiness (P<0.001 vs. controls) and improved health-related quality of life and mood. There was a decrease of 20-30% in episodes of depression among patients, and fewer days were lost due to ill-health.
‘It’s a big challenge in the field to have people use this treatment throughout the night,’ said McEvoy. ‘There’s some evidence that when you use it may be important. There are some studies showing that people who use it only in the first half of the night may not get benefit, particularly as it’s the latter part of the night when REM sleep is known to produce more severe OSA.’
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