Among the most serious complications of sleep apnea are the associated heart problems. The intermittent oxygen shortages trigger constriction of the blood vessels and stimulate the heart to work harder. The result is elevated blood pressure, additional stress on the heart, and the potential to dislodge deposits in the artery that can then travel to the brain, causing a stroke. As a result, people with sleep apnea have a five times higher risk of cardiovascular death than those without the condition.
CPAP (continuous positive airway pressure) has long been considered the best way to treat sleep apnea. Because the constant air pressure ensures a person won’t experience oxygen shortages as long as they wear the mask, it was thought that this would do the best job of reducing a person’s cardiovascular risk. However, a new study has cast doubt on that idea. The study results say that people with heart conditions experience no benefit from CPAP treatment.
Adding CPAP to Usual Care
Because sleep apnea is so strongly linked to cardiovascular problems, researchers wanted to show the benefit of adding sleep apnea treatment to the usual care for heart problems. Because CPAP is considered the best sleep apnea treatment, it was selected for this study.
Researchers recruited nearly 2700 patients age 45 to 75 at 89 clinics in several countries. These patients had moderate to severe sleep apnea and either coronary artery disease or cerebrovascular disease (stroke). The population was then randomized between receiving usual care and receiving usual care plus CPAP.
Patients were evaluated at the beginning of the study, then at follow-ups after six months, two years, four years, and at the end of the study. Their primary focus was on cardiovascular problems including cardiovascular death, heart attack, stroke, and hospitalization for cardiovascular problems. The results showed that, statistically, there was no difference between the group that received usual care and those who received usual care plus CPAP. Numerically, the CPAP group actually fared worse. In the CPAP group, 17% suffered one of the complications, compared to just 15.4% for the usual care group. The numbers were similar for cardiovascular death, which affected 1.9% of the CPAP group, compared to 1.5% of the usual care group. The difference is not statistically significant, but they certainly do not indicate that CPAP provided any benefit for these patients.
Is the Study Statistically Underpowered
Of course, part of the problem might be that the study doesn’t have the statistical power that researchers wanted. According to their calculations, they really needed 5000 patients to adequately detect the benefit of CPAP. But when they had trouble finding the number of patients they wanted, they recalculated their statistics. They determined that with a patient population of 2500, they would have a 90% chance of detecting a 25% benefit from CPAP. And the smaller the benefit of CPAP, the less likely it would be detected by a study of this size.
So this study can’t really say that there’s actually no benefit from CPAP, but it does seem to say that if there is one, it’s a small benefit.
Compliance Is Also a Problem
But the study was also plagued by the same problem that always dogs CPAP: compliance. Compliance was monitored for all patients, and it wasn’t good.
During the initial trial week for CPAP, patients wore their masks for an average of 5.2 hours a night. By the end of the first month, patients only wore their masks for an average of 4.4 hours per night, and by the end of the first year, patients were only wearing their masks for an average of 3.3 hours per night. In typical fashion, only 42% had what is considered adequate compliance with CPAP (wearing their mask for 4 hours per night).
Sleep Apnea Treatment You Will Use
On the other hand, oral appliances are much easier to use. Studies done using live monitoring of oral appliances show that 84% of users wear their appliance all night every night. When measured using the standard for CPAP use, oral appliances have a 95% compliance rate.