CPAP and Heart Health - the Truth vs. the Controversy

By Admin

The relationship between PAP therapy and heart health has been thoroughly studied, but results have varied, and researchers continue to debate the extent at which PAP-therapy can be associated with reductions in cardiovascular disease. Earlier this year, Clinical Corrections, the New York University Langone Journal of Medicine, published a response to some of the arguments against the link between CPAP and heart disease. One of the main points of contention, along with the limitations of some studies, was the issue of adherence. The rates of therapy compliance that are used during many studies are minimal by any standards, leading to poor results all around. In addition, there are many benefits of CPAP that affect heart health indirectly, by reducing the symptoms of related comorbidities. Looking at the bigger picture of overall health and longevity, it becomes clear that PAP therapy does affect cardiovascular health, but the results are difficult to measure. Rather than discounting the heart benefits of CPAP, doctors like Gregory Rubinfeld, M.D., author of the Clinical Corrections research, argue that further studies should be conducted using more rigorous adherence standards. This could finally clear up the controversy and give CPAP its due respect as a gold standard treatment with far-reaching benefits.

CPAP and Heart Health Connections

Sleep apnea is an increasingly prevalent disorder with documented benefits to cardiovascular health and related conditions. As a gold-standard treatment, PAP therapy reduces the apnea and hypopnea events associated with the disorder, but also decreases fatigue and sleepiness, normalizes sleep behavior, and improves health outcomes for numerous comorbid conditions. Left untreated, the disorder becomes a risk factor for hypertension, neurological disease, and cardiovascular mortality. In past studies, these associations have been linked to the effects of periodic arousals during sleep, as well as to oxygen saturation problems such as hypoxia and hypercapnia. Approximately 20 percent of those with obstructive sleep apnea (OSA), the most common form of the disorder, will develop pulmonary hypertension as well. And according to data collected by the Akershus Sleep Apnea Project, patients with OSA are 3 to 5 times more likely to develop abnormal heart rhythms such as atrial fibrillation or ventricular arrhythmias. These problems often develop during sleeping hours, but continue throughout the day. leading to high sympathetic activity that can overburden the heart and lead very easily to more serious conditions. Given the nature of these associations and comorbid relationships, it would appear likely that PAP therapy would have a comprehensive effect, and observations have confirmed this. One study, published in the American Journal of Respiratory Critical Care Medicine, reported a 64-percent cardiovascular risk reduction among patients using CPAP, independent from age or preexisting conditions. Other studies have shown improvements in insulin resistance and glycemic control, reductions in blood pressure and hypertension, and a lowered stroke volume, as well as a calming effect on the sympathetic nervous system that carries over into daytime activities. As blood-oxygen levels return to normal and sleep time is no longer disrupted by arousals, the effects on the heart and circulatory system become increasingly apparent. Many of the developments described above are quickly reversed through the use of CPAP.

The Debate Begins: CPAP and Healthy User Bias

While these treatment effects are measurable, a direct link between CPAP and cardiovascular mortality has not yet been established. While studies can collect data on the cardiovascular events of PAP-therapy patients, demands exist for randomized tests to prove these resulting correlations. In other words, the lack of randomization leaves room for criticism when any number of variables could have affected the results. But as Dr. Rubinfeld at Clinical Corrections points out in his research, the results from these studies were not derived from larger randomized controlled trials (RCTs). They were observational. This leaves findings open to other interpretations when nonrandomized selection biases are possible, especially when larger randomized trials produce results that contradict the findings of previous studies. In the case of CPAP and cardiovascular health, the findings of observational studies have been very consistent, but recent randomized trials have not supported the same conclusions.

The Sleep Apnea cardioVascular Endpoints (SAVE) Study

The Sleep Apnea CardioVascular Endpoints Study, often abbreviated as SAVE, was published in 2016 in the New England Journal of Medicine, and was the first major randomized control trial on the subject of PAP therapy for prevention of cardiovascular disease. The primary endpoint was a composite of various cardiovascular conditions, and followed approximately 3.7 years from its startup assessments. As expected, the PAP-therapy group saw reductions in daytime sleepiness, snoring, and apnea/hypopnea events by nearly 90 percent. But the findings saw little or no connection between the use of PAP therapy and cardiovascular outcomes. The results were highly controversial, and many news networks published stories about the limitations of CPAP for cardiovascular treatment. Even though PAP therapy is not prescribed as a cardiovascular treatment, the findings were presented as a discouragement for PAP-therapy proponents. Additional studies and meta-analyses followed, incorporating the SAVE data into their results, with some claiming an end to CPAP heart benefits. But as doctors and researchers began to assess the SAVE study endpoints, it became clear that its findings were based on low adherence levels. The average adherence level in the trials was only 3.3 hours per night.

While the standard adherence minimum for clinical purposes is 4 hours per night, 70 percent of time, many studies have recognized that even this amount can be limiting, especially for those with severe conditions. Even the SAVE study includes recommendations for further research in this area, and prior studies suggest that a higher minimum may support more quantitative benefits. Dr. Rubinfeld’s article in Clinical Corrections, published in February of this year, highlights the exceptionally low standard of therapy adherence in the SAVE trials, but he also mentions other limitations, such as the brief period of follow-up for health conditions that often progress at a gradual rate. While no study is completely flawless or inclusive of all possible variables, these parameters clearly limit the scope of the study’s findings. A subgroup analysis of those patients with higher levels of adherence (at least 4 hours) shows a predictable reduction in cardiovascular risk, and at rates consistent with prior studies (RR, 0.58; 95% CI, 0.34 to 0.99). Studies have since advocated for a higher standard in CPAP adherence, at least in respect to measured results in clinical trials.

Clinical Corrections

Most professionals in the area of sleep medicine agree that further studies are needed to accurately assess the relationship between sleep apnea and heart health, as well as to surrogate endpoints such as blood pressure, metabolic syndrome, and obesity. But evidence thus far appears to support the view that PAP therapy, when used regularly during sleep, leads to substantial benefits in cardiovascular health and risk reduction. While CPAP adherence problems remain a major issue and impediment to proper sleep apnea treatment, no patient is helped by flawed or limited methodologies. Clinical trials should be able to measure this relationship accurately, and without need for corrections that simply point out the obvious, that greater adherence leads to greater rewards.