03 Oct CPAP and Cardiovascular Health
To the many patients who use CPAP to treat obstructive sleep apnoea (OSA), the recently published article from the New England Journal of Medicine (NEJM) may be of concern. The article states that “therapy with CPAP plus usual care, as compared with usual care alone, did not prevent cardiovascular events in patients with moderate-to-severe obstructive sleep apnoea and established cardiovascular disease” (1). The research has picked up traction, not the lease on ABC (2). In other words, CPAP did not make any difference in preventing a stroke or heart attack in patients with existing cardiovascular disease. Before your patients go unplugging your CPAP devices, let’s take a careful look at this study.
Following attrition and exclusion, the study had approximately 2500 participants aged 45-75 (81% men) in 89 clinical centres across seven countries. All of the participants had pre-existing cardiovascular disease (this is an important point as the study does not look at the development of cardiovascular disease with CPAP therapy). The following people were excluded: people reporting excessive daytime sleepiness, significant oxygen drops on sleep testing (defined as lower than 80% oxygen saturation for more than 10 minutes of recording time on the sleep study), and people with significant congestive heart failure. What the researchers did was use a home sleep monitor to diagnose OSA and then an auto-titrating positive airway pressure (APAP) to determine the right CPAP pressure to treat those people who were found to have moderate or severe OSA.
So far, so good. But, here’s where the study becomes problematic. The mean usage time of CPAP for all participants was 3.3 hours. Compliance with CPAP therapy is measured at 4 or more hours of use per night. Only 42 percent of study subjects had “good adherence” to CPAP, but the results were analysed as if they had all used it. In June of last year, the American Academy of Sleep Medicine and Sleep Research Society published an editorial stating that adults should “obtain seven or more hours of sleep per night to avoid the health risks of chronic inadequate sleep.” A 2015 poll by the Sleep Foundation of Australia suggests that only 60% of Australians average 7 or more hours of sleep per night, while 85% average at least 6 hours per night. So even using that lower metric of 6 hours per night, the average participant in this study only used CPAP for just over half the time, on average, and the “good adherence” model averaged compliance for two-thirds of the night.
Let’s ruminate on this for a minute… If you saw a study stating aspirin is ineffective at preventing a heart attack or stroke and then found that the participants only averaged using aspirin half the time, you would naturally conclude that perhaps the problem is adherence, not the therapy. Indeed, the authors themselves state “although [an average of 3.3 hours per night of CPAP use] exceeded the estimates in our power calculations, it may still have been insufficient to provide the level of effect on cardiovascular outcomes that had been hypothesised.”
Several publications have demonstrated that when CPAP therapy is used adequately, it does reduce the risk of subsequent stroke. Patients with moderate-to-severe OSA who were admitted to hospital for stroke and used CPAP had a lower risk of subsequent strokes than those who did not. Another study showed that those with stroke and OSA had greater improvement in function after 30 days if they used CPAP for at least 6.5 hours per night compared to those that did not.
There is abundant research showing that OSA increases the risk of cardiovascular disease. One study showed the lifetime risk of heart attack doubles if OSA is untreated and triples if the OSA is severe. Another study showed that untreated moderate-to-severe OSA increases the lifetime risk of a stroke by a factor of four. Also, the Sleep Heart Health Study (which is considered the capstone study on cardiovascular risk from OSA) showed that men with untreated OSA have more than double the lifetime stroke risk compared to men without OSA.
What is amazing about these findings is that sleepy people were excluded from the study, and yet people still reported improvement in sleepiness, depression, anxiety, and work attendance… even with only 3.3 hours of CPAP use per night! What that demonstrates is that even partial CPAP therapy leads to important improvements in health. The studies referenced above also demonstrate that OSA presents real cardiovascular risk, and appropriate CPAP usage reduces the risk of heart attack and stroke.
What medical researchers need to focus on is how to make it easier for patients to become adherent to CPAP. National statistics on adherence to CPAP are terrible, with some studies showing that as many as 83 percent of patients prescribed CPAP fail to use it for at least 4 hours per night. If there’s one thing this article proved, it is that haphazard use of CPAP may not be sufficient to protect individuals with pre-existing cardiovascular disease from recurrence of stroke or heart attack.
So before your patients stop using their CPAP device, remember that poor use of CPAP may not protect them from cardiovascular disease.
Sources:
- McEvoy RD et al. “CPAP for Prevention of Cardiovascular Events in Obstructive Sleep Apnea.” N Eng J Med. Aug 28, 2016.
2.http://www.abc.net.au/news/2016-08-28/cpap-machines-do-not-reduce-risk-of-heart-attack-or-stroke/7792624
3.Martínez-García M, Campos-Rodríguez F, Soler-Cataluña J, Catalán-Serra P, Román-Sánchez P, Montserrat J. “Increased incidence of nonfatal cardiovascular events in stroke patients with sleep apnoea: effect of CPAP treatment.” Eur Respir J. 2012;39:906-912.
- Minnerup J, Ritter M, Wersching H, Kemmling A, Okegwo A, Schmidt A, Schilling M, Ringelstein E, Schäbitz W, Young P, Dziewas R. “Continuous positive airway pressure ventilation for acute ischemic stroke: a randomized feasibility study.” Stroke. 2012;43:1137-1139.
- Yaggi H, Concato J, Kernan WN, et al. “Obstructive sleep apnea as a risk factor for stroke and death.” N Engl J Med 2005; 359:2034-2041.
- Arzt M, Young T, Finn L, Skatrud JB, Bradley C. “Association of sleep-disordered breathing and the occurrence of stroke.” Am J Resp Crit Care Med. 172:1447-1451.
- Redline S, Yenokyan G, Gottlieb DJ, Shahar E, O’Connor GT, et al. “Obstructive sleep apnea-hypopnea and incident stroke: The sleep heart health study. American Journal of Respiratory and Critical Care Medicine. 182(2), 269-77.
- Weaver TE, Grunstein RR. “Adherence to continuous positive airway pressure therapy: the challenge to effective treatment.” Proc Am Thorac Soc. 2008;5(2):173.