Does CPAP reduce cardiac events in patients with obstructive sleep apnea?
There is no rigorous trial (or any prospective clinical trial) demonstrating CPAP reduces major cardiac events. However, this negative NEJM study has some issues (less than other referred to studies): the target n was halved, it was 80% men (prevalence is 3x higher in men before age 60, a lot of CV clinical trials have more men, and is there a specific sex-effect modifier known between men and women regarding sleep apnea and CV outcomes; for this trial the subgroups is buried in the supplementary material with no obvious effect modifier), and the treatment arm only used CPAP 3 hrs/night (we consider at least 4 to be "good" compliance; compliance is always better in trial and worse in the real world, shows how noncompliant people really are with this therapy being pushed and the need for better therapies).
Even with that, there was improved mental health and QOL in the CPAP-treated patients (sure can you tell me what a difference of 0.4 and 0.8 in the Mental Health scales and a 0.9 and 1.2 in the SF36 clinically mean or if they are clinically significant; also there is no Sham used for these subjective feelings). I wonder if the curves would have diverged if the authors had studied more people (the estimate size was towards HARM with a HR 1.1 and followed up to 84 months out, to me there is no expectation of divergence, further the confidence interval says truth could be at best a 9% relative improvement. If you assumed a 15% event rate as seen in the trial and needed to detect a 9% relative benefit with the usual power for a trial you would need about 21,000 enrolled individuals in the trial to identify such a benefit! I'm not sure who would sponsor that study. There's an editorial for this paper you can read by sleep experts going over the "problems" with the trial - sleep doctors certainly wouldn't have a bias from their field on the negative findings.
Figure 2. Cumulative Event Curve of the Primary End Point
Although admittedly a retrospective study of a specific group, this JACC paper looked at the effect of CPAP on patients with afib after an ablation, and found that using CPAP resulted in event rates comparable to not having OSA at all (and that OSA patients who didn't use CPAP had rates comparable to folks who didn't get ablated).
More limitations in this paper then the clinical trial above, 30 people per study arm, retrospective, selection of control groups not clear, unadjusted confounders, no controlled CPAP data or intervention, small numbers do not allow for model fitting, however this is a reasonable hypothesis generating paper for those with known afib trying rhythm control strategy, but I also argue what utility is Afib ablation anyway (another subject for another time). For new afib there was no difference in the much large clinical trial in the NEJM paper.
Figure 2. Kaplan-Meier Survival Curves According to Treatment Group
My bottom line is that I will continue to encourage my patients with OSA to use their CPAP. Sure, you have to individualize to your patients and if they have symptomatic daytime sleepiness and $3000 to burn for sleep study and equipment then CPAP can help their sleepiness and associated mood; however we should require better science, after all there was evidence that treatment with other positive pressure modality for sleep disordered breathing in HF actually HARMED and KILLED people. The literature about benefit in stroke patients is a little more compelling (not from the clinical trial, more strokes in CPAP arm), so I'm including a meta-analysis (Garbage in-Garbage out when it comes to meta-analyses) on that as well, as a bonus paper.
Cowie MR, Woehrle H, Wegscheider K, Angermann C, d’Ortho MP, Erdmann E, Levy P, Simonds AK, Somers VK, Zannad F, Teschler H. Adaptive servo-ventilation for central sleep apnea in systolic heart failure. New England Journal of Medicine. 2015 Sep 17;373(12):1095-105.)
Fein AS, Shvilkin A, Shah D, et al. Treatment of obstructive sleep apnea reduces the risk of atrial fibrillation recurrence after catheter ablation. Journal of the American College of Cardiology. 2013;62(4):300-305.
McEvoy RD, Antic NA, Heeley E, et al. CPAP for Prevention of Cardiovascular Events in Obstructive Sleep Apnea. New England Journal of Medicine. 2016;375(10):919-931.
