Tofool Alghanem DDS, MS
Oral appliance (OA) treatment for mild to moderate obstructive sleep apnea (OSA) improves blood pressure (BP) with effects comparable to those reported using CPAP treatment.
In adult patients with OSA, does the use of OA compared to CPAP lower blood pressure?
The reviewers searched the PubMed database for studies about the effects of OA on systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial blood pressure (MAP) published through December 15, 2011. They only included papers if all three reviewers agreed that the studies included adult patients 18 years and older, and pre-intervention and post-intervention data on SBP, DBP and MAP were available. The reviewers resolved disagreement through discussion. They excluded all case reports, case series, review articles, as well as studies that did not include standard deviations. The reviewers extracted data from two randomized control trials (RCTs) and five observational studies for their meta-analysis. The extracted data included age, sex, baseline BP, body mass index (BMI), and severity of OSA as reported by apnea-hypopnea index (AHI) for all participants. The reviewers performed meta-analysis of the combined results from RCTs and observational studies by estimating the mean difference before and after the intervention for the primary outcomes SBP, DBP, and MAP. Additionally, the reviewers mathematically combined the results on the secondary outcome nocturnal DBP of the control versus the intervention group of the RCTs. The reviewers constructed funnel plots to assess publication bias.
A total of seven studies that enrolled 399 participants met the inclusion criteria. The pooled estimate of mean changes from baseline of SBP, DBP, and MAP from each trial were -2.70 mm Hg (95% confidence interval (CI): [-4.60,-0.80]); -2.70 mm Hg (95% CI: [-4.60,-0.90]); and -2.40 mm Hg (95% CI: [-4.01,-0.80]), respectively. The pooled estimate of mean changes from baseline for nocturnal SBP, DBP, and MAP from each trial were -2.00 mm Hg (95% CI: [-5.30,1.10]); -1.70 mm Hg (95% CI: [-3.20,-0.10]); and -1.90 mm Hg (95% CI: [-5.10,1.30]), respectively.
Oral appliance treatment for mild to moderate sleep apnea improves BP control. Reductions in both SBP and DBP, as well as in nocturnal SBP were seen with OA treatment. Although the reductions in BP with OA were minimal, these effects were comparable to those reported with CPAP treatment.
Source of Funding:
No source of funding was disclosed.
Importance and Context:
Obstructive sleep apnea, a life threatening disease, has been treated with OAs. The effect of this treatment on physiological functions needs to be evaluated, since OSA affects the entire body. The current gold standard treatment for obstructive sleep apnea is continuous positive airway pressure (CPAP), which provide flow of air to the patients while asleep. However, tolerance and compliance are major issues related to the use of CPAP, hence the oral appliances started to be used as an alternative treatment for patients with mild to moderate sleep apnea.
Strengths and Weaknesses of the Systematic Review:
The authors of this systematic review searched a single database, and did not include gray literature; hence relevant studies could be missing. Inclusion and exclusion criteria were not well defined. This SR included mainly observational studies (five) and only two RCTs. A major problem with observational studies is confounding, the presence of which might have influenced the results. The authors did not assess study quality or risk of bias. They performed tests for heterogeneity among studies and assessed the possibility of publication bias; however, construction of funnel plots for fewer than 10 studies is not recommended. Since the included studies exhibited heterogeneity in terms of methods and follow-up, fixed-effect meta-analysis and quantitative synthesis combining studies of different designs are not appropriate. Lastly, meta-analysis of changes from before treatment to after treatment is not scientifically valid.
Strengths and Weaknesses of the Evidence:
There are many confounders, such as different OA mechanics, that might affect blood pressure levels; an RCT design is the most appropriate to determine if oral appliance therapy has an effect on blood pressure in patients with OSA. The small number of RCTs in this review possibly indicates a lack of high quality evidence about the effect of oral appliances on blood pressure. The review authors chose outcomes that were not reported in all included papers, which further reduced the eligible data for certain outcomes. More importantly, change from before treatment to after treatment was mainly used for quantitative synthesis instead of comparisons between exposed and unexposed or intervention and control groups. Sample sizes varied greatly between studies, which has an impact on the precision of the estimates.
Implications for Dental Practice:
While this systematic review found that there might be a mild benefit to BP associated with oral appliance use, it is more important that the dentist focus on the primary symptoms of OSA when using an appliance during the treatment. While initial results appear promising, more research is needed to understand the effect of OA therapy on patients' systemic conditions during the treatment of OSA. References: 1. Barewal RM, Hagen CC. Management of snoring and obstructive sleep apnea with mandibular repositioning appliances: A prosthodontic approach. Dent Clin North Am. 2014;58:159-80.
2. Higgins J, Green S. (editors). Cochrane Handbook for Systematic Reviews of Interventions. Version 5.1.0 [updated March 2011]. The Cochrane Collaboration, 2011. Available from www.cochrane-handbook.org.
3. Bland JM, Altman DG. Comparisons against baseline within randomized groups are often used and can be highly misleading. Trials. 2011; 12:264.