CPAP does not prevent CV events in obstructive sleep apnoea patients
medwireNews: Treatment with continuous positive airway pressure (CPAP) improves quality of life but does not prevent cardiovascular (CV) events for patients with moderate-to-severe obstructive sleep apnoea and established CV disease, trial data show.
In an editorial that accompanies the SAVE study results, Babak Mokhlesi (University of Chicago, Illinois, USA) and Najib Ayas (University of British Columbia, Vancouver, Canada) say that “prescribing CPAP with the sole purpose of reducing future cardiovascular events in asymptomatic patients with obstructive sleep apnoea and established cardiovascular disease cannot be recommended” on the basis of these findings.
The study included 2717 patients recruited from 89 clinical centres in seven countries who were randomly assigned to receive CPAP plus usual care or usual care alone. All patients were aged between 45 and 75 years (mean 61 years, 81% men) and had moderate-to-severe obstructive sleep apnoea along with coronary artery or cerebrovascular disease.
During a mean follow-up period of 3.7 years, 229 (17.0%) patients in the CPAP group and 207 (15.4%) in the usual-care group experienced a primary endpoint event, which was a composite of CV death, myocardial infarction, stroke, or hospitalisation for unstable angina, heart failure or transient ischaemic attack.
This was not a significant difference and there were also no significant differences between the treatment groups in any of the cause-specific endpoints.
Patients in the CPAP group did, however, experience a significant decrease in their mean apnoea–hypopnea index from 29.0 events per hour of recording at baseline to 3.7 events per hour during follow-up.
This benefit was accompanied by significantly greater reductions from baseline in sleepiness, anxiety and depression. Indeed, the proportion of patients with clinically relevant depression scores on the Hospital Anxiety and Depression Scale was 25% to 30% lower in the CPAP group than in the usual-care group at the end of the study.
Furthermore, the patients who received CPAP had significantly greater improvements on the physical and mental subscales of the 36-item Short-Form Health Survey quality of life questionnaire and fewer days off work because of poor health than those who received usual care.
The mean duration of CPAP adherence was 3.3 hours per night, which “may not be adequate to prevent cardiovascular events”, Mokhlesi and Ayas remark.
Indeed, a prespecified analysis showed that the 561 patients who were classed as adherent to CPAP (≥4 hours per night) had a significantly lower risk of stroke and cerebrovascular events than 561 propensity score–matched patients from the usual-care group, at hazard ratios of 0.56 and 0.52, respectively.
The team, led by Doug McEvoy (Adelaide Institute for Sleep Health), points out in the New England Journal of Medicine that these results were not adjusted for multiple testing. But the researchers also note that the findings are consistent with those from two other randomised trials that showed no reduction in CV events overall with CPAP but better outcomes among patients who were adherent to CPAP therapy.
By Laura Cowen
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