By Barbara Phillips, MD, MSPH
Professor of Medicine, University of Kentucky; Director, Sleep Disorders Center, Samaritan Hospital, Lexington
Dr. Phillips reports no financial relationships relevant to this field of study.
SYNOPSIS: In this meta-analysis of 51 randomized, controlled studies that included nearly 5000 patients, continuous positive airway pressure and oral appliances resulted in comparable and statistically significant reductions in blood pressure.
SOURCE: Bratton DJ, et al. CPAP vs mandibular advancement devices and blood pressure in patients with obstructive sleep apnea: A systematic review and meta-analysis. JAMA 2015;314:2280-2293.
This report is the result of a meta-analysis of 51 studies evaluating the effect of two treatments — continuous positive airway pressure (CPAP) and oral appliances (also known as mandibular advancement devices or MADs) — on blood pressure in patients with obstructive sleep apnea (OSA). To be included in the analysis, studies had to contain adult patients with OSA (defined as an apnea-hypopnea index of ≥ 5/h) randomized to at least two of the following treatments: 1) CPAP, 2) oral appliance, or 3) control. The authors reported the treatment on both systolic blood pressure (SBP) and diastolic blood pressure (DBP). The authors also examined duration of hours/night of CPAP use and blood pressure. Including only patients with a diagnosis of hypertension apparently was not a prerequisite for inclusion in this analysis. The authors had to perform fancy statistical footwork in cases where studies reported the difference in blood pressure between treatments but not the absolute change in SBP and DBP.
Forty-four of the 51 studies compared CPAP with a control. Only three evaluated oral appliances compared with control. One compared CPAP with oral appliances, and three compared CPAP, oral appliances, and controls. Mean blood pressure was fairly consistent between studies.
Compared with controls, CPAP was associated with a reduction in SBP of 2.5 mmHg (P < 0.001) and oral appliances were associated with a reduction of 2.1 mmHg (P = 0.002). CPAP was associated with a reduction in DBP of 2.0 mmHg (< 0.001) and oral appliances were associated with a reduction in DBP of 1.9 mmHg (P = 0.008). There was no significant difference between CPAP and oral appliances in the reduction of blood pressure in intention-to-treat comparisons.
CPAP compliance (or adherence) made a difference. Mean CPAP use (hours/night) could be obtained from 44 of the 47 studies of CPAP. A 1-hour-per-night increase in mean CPAP use was associated with an additional reduction in SBP of 1.5 mmHg (P < 0.001) and an additional reduction in DBP of 0.9 mmHg (P = 0.001).
Whether the patient was hypertensive also made a difference. The association of CPAP with reductions of both SBP and DBP was greater in patients with higher baseline blood pressure levels, although there was no difference between the reported treatment effects in this subgroup of trials that included only patients who had a diagnosis of hypertension. The authors also reported no difference in effect by severity of sleep-disordered breathing.
There were some weak signals that CPAP might be more effective than oral appliances in some situations. The authors reported “ … there was some suggestion that the effect of CPAP reported in the studies was larger in those in which morning blood pressure data were extracted.” In addition, the primary analysis was a network analysis. The authors also performed a pairwise analysis and found similar results, except for a smaller reduction in DBP of -1.1 mmHg (P = 0.11).
COMMENTARY
OSA is a prevalent and deadly condition. Recent estimates of prevalence are about 10%, depending on the population studied.1 Treatment of OSA with CPAP is associated with improved outcomes from many important consequences, including motor vehicle collisions , atrial fibrillation, hypertension, and overall mortality in men, women, and the elderly.2-7
But CPAP is a burdensome treatment. Overall, adherence to CPAP is probably slowly improving because of increased efforts at education and follow-up, but CPAP use is still much less than optimum. Further, patients with mild sleep apnea are less likely to suffer medical consequences and also are less likely to be able to adhere to CPAP. Mandibular advancement devices (better known as “oral appliances”) are a reasonable alternative to CPAP for those who are CPAP-intolerant or who have mild disease.
Hypertension is the best-proven consequence of untreated sleep apnea and likely contributes to OSA’s link to cardiovascular disease and stroke. Treatment for sleep apnea that does not result in improvement in hypertension cannot be considered truly effective treatment. This paper supports the use of oral appliances in lieu of CPAP in OSA patients who suffer from hypertension. It does not demonstrate that oral appliances reduce the risk of many of the other well-documented complications of OSA. Such data are still sparse and take a long time to generate. But the fact that these devices have been demonstrated to improve sleep-disordered breathing and blood pressure to a similar extent as CPAP strongly suggests that they reduce other risks as well.
There are some practical issues to consider. Some knowledge of local dentists and their approach to this issue is helpful. Not all dentists craft oral appliances. Some confuse them with bite guards for bruxism (not the same thing at all). Some will offer the patient a “boil and bite” or “off the shelf” device; these have been shown to be less effective than custom-made, adjustable devices. In our practice, we use a handout that lists dentists in our area who craft oral appliances well and who follow-up with their patients (because the “bite” can change, which is apparently a big deal to dentists). Our handout also lists some questions to ask their personal dentist, if they are going that route (“How many have you made? Is it custom made and adjustable?”). In general, it takes a few months to deliver and titrate a device, so this might not be the best option for a patient who has severe sleep apnea and is falling asleep at the wheel today. Some dentists cannot craft these devices for edentulous patients, though some will. We ask patients to come back after the device has been delivered and adjusted, and sometimes (not always, depending on insurance and symptoms) undertake a portable sleep study (cheap, quick) to assess efficacy.
I still recommend CPAP as first-line therapy for OSA, and some signals in this paper suggest that CPAP is still the better choice for people who have difficult-to-control blood pressure and who are likely to be adherent. But for people who are CPAP-intolerant or who have mild disease, oral appliances are much better than nothing, which is essentially what they are going to receive unless they are offered an alternative. Additionally, oral appliances are vastly superior to upper airway surgery,8 which I do not consider to be a viable alternative.
Oral appliances are not just less burdensome for the patient, they are far less burdensome to the prescribing physician. In the United States, a physician who prescribes CPAP is currently expected to more or less police such CPAP use and to attest that the patient is using it (by objective measurement) and benefitting from it within 3 months of its initiation, all on an annual basis. “CPAP compliance visits” are a huge and often unpleasant part of my practice. With an oral appliance, one simply writes the prescription, recommends a dentist, and asks the patient to come back for follow-up after the device is delivered and titrated. Looking ahead, I predict there will be many more oral appliance prescriptions and fewer CPAP prescriptions. Looking even farther ahead, I predict that patients will be buying CPAP off the shelves at big box stores.
REFERENCES
- Peppard PE, et al. Increased prevalence of sleep-disordered breathing in adults. Am J Epidemiol 2013;177:1006-1014.
- Tregear S, et al. Continuous positive airway pressure reduces risk of motor vehicle crash among drivers with obstructive sleep apnea: Systematic review and meta-analysis. Sleep 2010;33:1373-1380.
- Holmqvist F, et al. Impact of obstructive sleep apnea and continuous positive airway pressure therapy on outcomes in patients with atrial fibrillation — Results from the Outcomes Registry for Better Informed Treatment of Atrial Fibrillation (ORBIT-AF). Am Heart J 2015;169:647-654.
- Fava C, et al. Effect of CPAP on blood pressure in patients with OSA/hypopnea a systematic review and meta-analysis. Chest 2014;145:762-771.
- Marin JM, et al. Long-term cardiovascular outcomes in men with obstructive sleep apnoea-hypopnoea with or without treatment with continuous positive airway pressure: An observational study. Lancet 2005;365:1046-1053.
- Campos-Rodriguez F, et al. Cardiovascular mortality in women with obstructive sleep apnea with or without continuous positive airway pressure treatment: A cohort study. Ann Intern Med 2012;156:115-122.
- Martínez-García MA, et al. Cardiovascular mortality in obstructive sleep apnea in the elderly: Role of long-term continuous positive airway pressure treatment: A prospective observational study. Am J Respir Crit Care Med 2012;186:909-916.
- Walker-Engstrom ML, et al. 4-year follow up of treatment with dental appliance or uvulopalatopharyngoplasty in patients with obstructive sleep apnea: A randomized study. Chest 2002;121:739-746.
In this meta-analysis of 51 randomized, controlled studies that included nearly 5000 patients, continuous positive airway pressure and oral appliances resulted in comparable and statistically significant reductions in blood pressure.
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