Reference: Lancet Respir Med. 2020 Apr;8(4):359-367
Continuous positive airway pressure (CPAP) for obstructive sleep apnea (OSA) reduces the disease-oriented outcomes of blood pressure, arrhythmias, and left ventricular load. The prevalence of sleep apnea in patients with coronary artery disease is high, and it has been assumed until recently that using CPAP to treat OSA would reduce cardiovascular morbidity and mortality. However, a recent review of several good studies by Parsons et al. suggests that CPAP for symptomatic OSA has no benefit in secondary prevention of cardiac disease.
A new study enrolled 2,551 patients admitted for acute coronary syndrome (ACS) to 15 hospitals in Spain and performed overnight respiratory polygraphy to examine the effects of CPAP on patients with ACS and OSA but mild or no daytime sleepiness. All enrollees received usual care for ACS, and participants who screened positive for OSA were randomized to CPAP (n = 633) or no CPAP (n = 631). The primary outcome evaluated was a composite of cardiovascular events, including cardiac death, heart failure, MI, stroke, TIA, or repeat admissions for ACS. Data were evaluated using an intention to treat analysis.
There were no statistically or clinically significant differences in the risk ratios for either group. Adherence with CPAP was an issue, however. In general, participants were very good about attending follow-up appointments, but those assigned to the CPAP group had a mean adherence of only 2.78 hours/night using their machines. In fact, of those who experienced events in the CPAP group, a mere 37.6% had been using the CPAP for 4 hours or more per night.
The lack of adherence to the primary intervention is a significant limitation of this study. Conclusions about the effects of CPAP in adherent patients would require a sham CPAP set-up to control for the fact that adherent patients do better regardless of the intervention. It’s admittedly difficult to get patients to adhere to unpleasant treatments like CPAP, and even more so when they are asymptomatic. Recent research supports the notion that adherence is lower with CPAP if patients do not have daytime drowsiness and if training on use of CPAP is brief and provided only once, as in this trial. Unfortunately, this study isn’t quite the wake-up call a cursory read of this Lancet article might suggest.
For more information, see the topic Cardiovascular Disease and Obstructive Sleep Apnea in DynaMed.
DynaMed EBM Focus Editorial Team
This EBM Focus was written by Dan Randall, MD, Deputy Editor for Internal Medicine at DynaMed. Edited by Alan Ehrlich, MD, Executive Editor at DynaMed and Associate Professor in Family Medicine at the University of Massachusetts Medical School, and Katharine DeGeorge, MD, MS, Associate Professor of Family Medicine at the University of Virginia and Clinical Editor at DynaMed.