People with obstructive sleep apnea have an increased risk of cardiovascular diseases. Researchers investigate whether oral appliance therapy can alleviate the burden.
By Regina Patrick, RPSGT, RST
People with obstructive sleep apnea (OSA) have an increased risk of developing cardiovascular diseases such as hypertension, stroke, heart failure, arrhythmias, atrial fibrosis, atrial fibrillation, enlarged left ventricles, and arterial stiffness.1,2,3 Logically, preventing episodes of OSA should reduce the risk of cardiovascular disease, but study findings are mixed.4
Because CPAP therapy has such a high efficacy rate for OSA,4 research has focused on the effects of CPAP on cardiovascular outcomes, and some studies indicate improved cardiovascular outcomes.5,6 For example, Shukla et al demonstrated that, among patients with OSA who had been previously treated for atrial fibrillation, CPAP use reduced the risk of recurrence of atrial fibrillation by 42%.7
But some patients find CPAP intolerable and forgo treatment or look for alternatives. An attractive alternative therapy is oral appliances, which typically push the jaw and/or tongue forward to maintain open airways. Whether oral appliance therapy can improve cardiovascular outcomes has not been studied in depth. But there are some new findings, and more studies are underway now.
Both CPAP and oral appliances have been shown to reduce the severity of OSA episodes, as measured by the apnea-hypopnea index (AHI). On average, CPAP decreases the AHI more.8 Some research indicates that the risk of cardiovascular disease increases as the severity of OSA (as measured by AHI) increases.9 But AHI is not necessarily a good predictor of cardiovascular events: Some investigators have demonstrated that a reduction in AHI with OSA treatment is not necessarily linked with a reduction in cardiovascular risk.10
“I don’t think anybody has shown in the literature that the reduction in AHI scores, from an outcome perspective, has demonstrated a reduction in cardiovascular events or in all-cause mortality,” says Mark Murphy, DDS, chief growth officer of oral appliance maker ProSomnus Sleep Technologies. “That’s really a problem because we’re chasing this metric, AHI, the number of events per hour, but it turns out we’re probably chasing the wrong metric.”
Sleep apnea-specific hypoxic burden may be a more accurate measure,11 Murphy says. The hypoxic burden is the depth and amount of time spent in a desaturation period. Sleep apnea-specific hypoxic burden values are expressed as minutes of percent desaturation per hour (%min/h). For example, a hypoxic burden of 20 %min/h can represent 20 minutes of 1% desaturation per hour or five minutes of 4% desaturation per hour.
In other words, imagine two people with OSA (John and Jane) have an AHI of 30. Both start at an SaO2 level of 92% before the apnea event. During the apnea, John desaturates to 88% over a period of 10 seconds, whereas Jane desaturates to 80% over a period of 25 seconds. Jane has a greater sleep apnea-specific hypoxic burden because of the greater fall in the SaO2 level and the longer duration of the hypoxic event. At least one study found that sleep apnea-specific hypoxic burden predicted incident heart failure in men, whereas AHI did not.11
ProSomnus recently funded a study that demonstrated a reduction in the sleep apnea-specific hypoxic burden using its precision oral appliance therapy. In the study, headed by Erin Mosca, PhD, ProSomnus director of scientific and medical affairs, the ProSomnus [IA] device reduced AHI from 29.1 to 10.5 and the sleep apnea-specific hypoxic burden from 81.8 to 27.3. Based on AHI of less than 15, therapeutic efficacy was achieved in 85% of participants and, based on AHI of less than 10, in 76%. But if efficacy is defined as sleep apnea-specific hypoxic burden of less than 53, the therapeutic efficacy of the oral appliance increased to 91%—implying that using AHI as the efficacy measure may misclassify some patients as oral appliance nonresponders.12
Among the existing research regarding cardiovascular outcomes with oral appliances, a relatively well-studied topic is the therapy’s impact on blood pressure. A narrative review published in 2022 notes that data from individual studies have been inconclusive, but systematic reviews and meta-analyses have reported modest reductions in blood pressure by oral appliances compared with baseline. “Studies regarding the effect of [oral appliance] therapy on blood pressure (BP) are not sufficient and have shown conflicting results depending on study design, BP measurement method, or OSA severity of the included patients,” the authors write.13
In response to the need for more information on oral appliances’ potential impact on cardiovascular health, the Oral Appliance Network on Global Effectiveness (ORANGE) study has started its data collection from centers across the globe. ORANGE, whose protocol development was supported by the American Academy of Dental Sleep Medicine, is a multinational, multicenter observational cohort study developed to evaluate the long-term effectiveness of oral appliance therapy in patients with OSA and assess long-term health outcomes of the therapy related to cardiovascular disease. As of November 2022, it has enrolled 163 patients from four research centers.14
Once more clinical research data is available, clinicians can provide more appropriate and effective care to patients with OSA, particularly those who also have cardiovascular diseases and opt for oral appliance therapy.
Regina Patrick, RPSGT, RST, is a freelance medical editor and writer.
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