New Studies Focus on CPAP Cardiovascular Benefits

By Admin

According to new research presented at the American Thoracic Society (ATS) 2021 International Conference, CPAP therapy reduces the risk of heart attack and stroke for some patients, particularly those with a hIgh pulse-rate response to sleep apnea events. This means that patients who respond to apnea events with accelerated heart rates are most likely to experience reduced risk of heart disease and stroke from CPAP therapy. These findings, gained from a re-analysis of previous studies concerning PAP therapy cardiovascular benefits, comes at a time when questions have been raised about what constitutes a clinically important outcome for CPAP therapy. Despite a 155-page draft technology assessment prepared by the Agency for Healthcare Research and Quality (AHRQ) that specifically questions the cardiovascular benefits of CPAP, a collection of top sleep-health organizations including the American Academy of Sleep Medicine (AASM), the American Association of Sleep Technologies (AAST), and the World Sleep Society have published a response letter defense of the many years of clinical evidence supporting CPAP health benefits beyond the cessation of apneas. The evidence presented at the ATS 2021 International Conference targets this issue specifically, using previous studies to support the extended benefits of long-term treatment adherence. In addition, the study authors plan to use this evidence as a starting point for further research in this area.

The Findings

The research presented at ATS 2021 demonstrates that patients with elevated pulse-rate responses to sleep apnea events are more likely to experience cardiovascular benefits from therapy. Those with a higher respiratory event-related pulse rate response experienced an over 50 percent risk reduction for cardiovascular events when using CPAP, versus those not using CPAP. The results further indicated that patients with non-sleepy conditions (those without excessive sleepiness symptoms) tended to benefit more as well. This led to the conclusion that a specific phenotype—those with non-sleepy conditions and high pulse-rate responses—experience clear reductions in the risk of heart disease and stroke with long-term use of CPAP. Having established that this group of patients experience additional health benefits beyond the cessation of apnea and hypopnea events, the study authors conclude that further research should explore more extended benefits for therapy in general, either through new studies or exploring existing evidence in support of CPAP benefits.

Lead investigator Ali Azarbarzin, Ph.D., from the Division of Sleep and Circadian Disorders at Brigham and Women's Hospital in Boston, concluded in the presentation that the study “provides novel evidence that a greater heart rate responsiveness to obstructive (airway) events is an identifiable, deleterious, and potentially reversible risk factor that could be used to select patients most likely to exhibit long-term CV benefit from CPAP therapy.”

Prof. Azarbarzin also addressed the possible flaws in the AHRQ draft report, suggesting that reliance upon the apnea-hypopnea index (AHI) may have limitations, but should be considered alongside other, more specific physiological parameters such as heart rate and heart rate response to apneas. Additional measurements, Azarbarzin explained, such as elevated heart rate in response to events, can better highlight the heterogeneity in sleep apnea and identify those who experience additional benefits. As he explained it. “The greater the pulse rate response, the greater the calculated treatment benefit of CPAP."

Since many sleep apnea patients also have heart disease or other cardiovascular conditions, the extended benefits of PAP therapy are important considerations and a means of encouragement for continued treatment adherence. Research supports a number of benefits for PAP therapy including risk reduction for arterial stiffness, age-related dementia, depression, and associated mortality as well as its primary purpose of reducing or eliminating apnea and hypopnea events. But heart health is a major concern for may sleep apnea patients, and this controversy over what evidence is clinically significant has many patients and providers waiting anxiously to see what further research will bring to light.

Pulse Rate, Sleep Apnea, and Comorbidities

Pulse rate is the wave of blood in the artery created by contraction of the ventricle during a cardiac cycle. The strength or amplitude of the pulse reflects the amount of blood ejected ( also called stroke volume). When this rate is raised, the heart is working harder to pump the blood, which can result in strain or high blood pressure. Over time, this can lead to further complications such as heart disease, cardiovascular disease, or stroke.

When coupled with heart disease, this increase in heart rate, or pulse rate, can raise a person's risk for heart attacks, strokes, and other cardiovascular problems, according to the research. Therefore, the role of CPAP in treating both the sleep-disordered breathing and related comorbid conditions is crucial for ongoing health and wellbeing. And Azarbarzin et al. emphasize this in in their concluding remarks, stating that heart disease, a leading cause of death in the U.S., not only affects the health and wellbeing of patients, but very often leads to early mortality.

While CPAP is only prescribed for sleep-related breathing conditions, comorbid conditions are often considered by the physician when making the recommendation, especially when patients are reluctant to treat sleep apnea alone. An example of this is when patients with non-sleepy OSA are not motivated to seek treatment, since condition is primarily experienced in an unconscious state. But when comorbid conditions are also considered, there may be more of an incentive to adhere to the prescribed treatment.

The Controversy

The ATS presentation, part of a larger discussion titled “Pathophysiology, Cardiovascular Disease, and COVID-19, What’s Happening in Sleep Research Right Now,” is particularly significant due to the AHRQ assessment, which put in question much of the evidence supporting cardiovascular benefits of CPAP.

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. As the American Academy of Sleep Medicine’s organized response to the AHRQ draft assessment states in its introduction, a proper evidence-based review “should assess the evidence for all outcomes that patients and clinicians are likely to consider important.” And few issues are more important to patient health than the cardiovascular effects of elevated heart rates due to sleep apnea.