KU medical informatics researcher publishes study in JAMA Network Open showing CPAP therapy is associated with a reduced risk of death for people with sleep apnea
Study looking at Medicare claims data for nearly 900,000 people with obstructive sleep apnea also found that those who used CPAP machines were less likely to have major cardiovascular events.
When someone has obstructive sleep apnea, their throat muscles relax and block their airway during sleep, triggering a survival reflex that causes them to wake up to breathe again. Not only do these repeated sleep interruptions cause a person to be tired during the day, but the sudden drops in blood oxygen also strain the cardiovascular system. Sleep apnea, which is also more prevalent in older people, is linked to higher rates of death and cardiovascular problems such as stroke and heart disease.
Continuous positive airway pressure (CPAP) therapy, in which a machine delivers a constant flow of air through a mask during sleep, is the first line of treatment for moderate to severe obstructive sleep apnea. Even though CPAP machines are effective in treating sleep apnea, randomized clinical trials have failed to demonstrate that they prevent cardiovascular problems.
But an observational study, published in JAMA Network Open Sept. 11, found that CPAP usage was associated with a significant reduction in mortality and major cardiovascular events, including heart attack, heart failure and stroke in Medicare patients with obstructive sleep apnea. The study, led by Diego Mazzotti, Ph.D., assistant professor of medical informatics in the Department of Internal Medicine at the University of Kansas Medical Center, is the first such study focused on older adults across the central United States. It’s also the largest study of its kind, with a sample size of nearly 900,000 people.
“We found that Medicare-eligible adults who have sleep apnea and started CPAP had about half the risk of dying over the next five years compared with those who never started using CPAP,” said Mazzotti. “And then, for people who had never had a prior major cardiovascular event, we found that those who started using CPAP had a lower risk of having a cardiovascular event in the next five years. The effect was smaller — they were about 10% lower-risk than the group that did not start CPAP — but the effect was still there.”
The researchers conducted their study by looking at fee-for-service claims data from 2011 through 2020 for Medicare beneficiaries who lived in nine central states that are part of the Greater Plains Collaborative, a clinical research network. Mazzotti noted that one of the strengths of the study was the large sample size. Using such a large volume of data, the researchers were able to design a study that could make inferences about the usage of CPAP and its clinical effects.
The researchers also found that among the people who started using CPAP, the highest utilizers — those who continued using their machines over the first year, as implied by their number of related Medicare claims — had the lowest risk of mortality and cardiovascular events compared with those who did not continue CPAP therapy. The study also indicated that the higher utilizers had a lower risk of major cardiovascular events, including heart attack, stroke and heart failure. “The more claims you had, the lower your risk,” Mazzotti said.
The strongest cardiovascular effect of starting to use CPAP was protection against myocardial infarction (heart attack); CPAP was associated with a 16% risk reduction. The study also showed that the people who got the most benefit from CPAP were those who had comorbidities, such as obesity or atrial fibrillation, and women. Mazzotti noted that explaining why women got more benefit from CPAP reveals one of the limitations of the study: It’s possible that women also engage in more healthy behaviors, such as physical activity and better diet, that could have contributed to their reduced mortality and cardiovascular risk, but these factors are not captured in the claims data. Another limitation is the fact that claims data may not always reflect actual usage.
Mazzotti is collaborating with another group of researchers in Utah to incorporate actual daily CPAP usage data gathered from manufacturers of CPAP devices. He and his colleagues can then use that more granular data to determine, for example, the effect of using a CPAP device for six hours per night versus four hours per night. “We should be able to address those kinds of questions in the future,” he said.