Predictors of long-term effectiveness to mandibular repositioning device treatment in obstructive sleep apnea patients after 1000 days

Does oral appliance efficacy in treating obstructive sleep apnea depend on the appliance specialist's experience?

PURPOSE

In France, oral appliances (OAs) are the first-line treatment for moderate and second-line treatment for severe obstructive sleep apnea-hypopnea syndrome. In general, the sleep specialist refers his/her patient to the appliance specialist for the impressions and the fitting. However, is there a relationship between the volume of activity of the appliance specialist and the efficacy of this device?

METHODS

Our unit includes seven appliance otolaryngology specialists whose activities are highly variable (number of patients varying by a factor of almost 10). Data from a prospective follow-up registry of patients treated with an OA for moderate and severe obstructive sleep apnea-hypopnea syndrome were studied, and differences in outcomes between practitioners in the team were sought.

RESULTS

Among 859 patients, OAs significantly reduced the apnea-hypopnea index. Even if the patients were not completely comparable from one practitioner to another, there was a significant heterogeneity in efficacy (complete or partial response of the apnea-hypopnea index and failure of OAs) between practitioners (p = 0.0038; 0.0011; 0.0007 respectively), with better results in practitioners with a higher level of OA activity.

CONCLUSION

The findings suggest that it may be preferable to refer patients to OA practitioners who see a higher volume of patients with moderate or severe obstructive sleep apnea-hypopnea syndrome treated with an OA.

Factors associated with treatment adherence to mandibular advancement devices: a scoping review

PURPOSE

Obstructive sleep apnea (OSA) is frequently treated with continuous positive airway pressure (CPAP) or mandibular advancement devices (MADs). For various reasons, both treatment options are often affected by low adherence. While factors associated with low CPAP adherence are described in the literature extensively, less is known about adherence to MAD therapy. This scoping review aimed to synthesize the body of literature on the factors associated with adherence to MAD treatment.

METHODS

A systematic literature search was conducted using bibliographic databases PubMed, Embase.com , Web of Science, and the Cochrane Library (Wiley) to identify relevant studies that described factors associated with adherence to MAD in the treatment of OSA or snoring combined with OSA in adults.

RESULTS

The literature search yielded a total of 694 references. Forty studies were found eligible for inclusion. The literature showed that factors with a possible negative influence on the adherence to MAD treatment are personality aspects; failing effectiveness of MAD; side effects during MAD therapy; using a thermoplastic MAD; dental treatments during MAD therapy; and a poor first experience with the MAD with inadequate guidance by professionals. Factors that may have a positive effect on MAD adherence include effectiveness of therapy, custom-made MAD, good communication skills of the practitioner, early recognition of side effects, stepwise titration of the MAD, and positive first experience with MAD.

CONCLUSIONS

The knowledge of factors associated with MAD adherence can be used to provide further insight into individual adherence to OSA treatments.

The role of oral appliance therapy in obstructive sleep apnoea

There is now widespread recognition within the world of sleep medicine of the increasing importance of dental sleep medicine and, in particular, the role of oral appliance therapy (OAT) in the management of adults with obstructive sleep apnoea (OSA). For the purpose of this review, the term OAT refers to a custom-made intra-oral appliance, which acts to posture the mandible in a forward and downward direction, away from its natural resting position. Whilst nasally applied continuous positive airway pressure remains the "gold standard" in nonsurgical OSA management, OAT remains the recognised alternative treatment.This review of OAT aims to provide an evidence-based update on our current understanding of their mode of action, exploring the potential anatomical and physiological impact of their use in preventing collapse of the upper airway; the current clinical practice guidelines, including the recently published National Institute of Clinical Excellence 2021 guidance, in conjunction with the American Academy of Sleep Medicine and American Academy of Dental Sleep Medicine; optimal design features, comparing the role of custom-made versus noncustom OAT devices and the importance of titration in achieving a dose-dependent effect; patient predictors, preference and adherence to OAT; its impact on a range of both patient- and clinician-centred health outcomes, with a comparison with CPAP; the limitations and side-effects of providing OAT; and, finally, a look at future considerations to help optimise the delivery and outcomes of OAT.

Patients with Obstructive Sleep Apnea and Cardiovascular Diseases: What, When, and Why Is Mandibular Advancement Device Treatment Required? A Short Review

Obstructive sleep apnea is a potentially dangerous condition with significant risks of comorbidities if left untreated. It represents a cardiovascular risk factor in the general population, and a higher prevalence is observed in patients already suffering from cardiovascular diseases. The gold standard treatment, continuous positive airway pressure, is not always accepted or tolerated. The mandibular advancement device represents an alternative treatment that we propose to implement in our study. The objective here is to first present a brief review of the topic. Due to poor evidence in the field, we propose a pilot study to evaluate the effect of a mandibular advancement device in patients with cardiovascular disease who are not treated for their sleep pathology in order to improve their therapeutic management.

Non-CPAP therapy for obstructive sleep apnoea

Treatment of obstructive sleep apnoea in adults is evolving, from a "one treatment fits all" to a more individualised approach. The spectrum of treatment options is broad and heterogeneous, including conservative, technological and pharmaceutical modalities. This raises the questions of which patients these modalities might be useful for, and if there are specific criteria for single or combined treatment. The most commonly used non-CPAP treatment is a mandibular advancement device. Furthermore, it appears from the available evidence that upper airway surgery, bariatric surgery, and maxillomandibular advancement can be effective in particular patient groups and should be indicated more readily in clinical practice. Technically, a tracheotomy is the most effective surgical treatment, but is not socially acceptable and is associated with major side-effects. Other treatment options are emerging, like positional therapy, hypoglossal nerve stimulation, and myofunctional exercises. Drug therapy is also promising when pathophysiological traits are considered. The range of currently available treatment options will be discussed in this review, with emphasis on the selection of appropriate patients, therapeutic efficacy and compliance, and reference to recent guidelines. In the selection process, routine application of drug-induced sleep endoscopy to assess the site(s) of collapse during sleep can increase the success rate of both surgical interventions and oral appliance therapy.

Educational aims

To outline recommendations concerning the proper management of obstructive sleep apnoea (OSA) patients that cannot be treated adequately with continuous positive airway pressure (CPAP) due to intolerance, poor adherence or compliance, or CPAP refusal.To provide information about the selection of appropriate patients for alternative non-CPAP treatment options.To better understand the different aspects of OSA treatment with noninvasive approaches, such as oral appliances, positional therapy, drug treatment and myofunctional therapy, including indications, contraindications, and expected short- and long-term results.To discuss the different surgical options for the treatment of OSA and to provide information on the important issue of proper patient selection for surgery, as most OSA surgical outcomes are associated with the pre-operative assessment of the level(s) of upper airway collapse.

Pilot Study of a New Mandibular Advancement Device

This study was conducted to determine the efficacy of a customized mandibular advancement device (MAD) in the treatment of obstructive sleep apnea (OSA). Eight patients (M = 3; F = 5; mean age = 56.3 ± 9.4) with a diagnosis of OSA confirmed by polysomnography (PSG) were recruited on the basis of the following inclusion criteria: apnea-hypopnea index (AHI) > 5, age between 18 and 75 years, body mass index (BMI) < 25, and PSG data available at baseline (T0). All were treated with the new NOA® MAD by OrthoApnea (NOA®) for at least 3 months; PSG with NOA in situ was performed after 3 months of treatment (T1). The following parameters were calculated at T0 and T1: AHI, supine AHI, oxygen desaturation index (ODI), percentage of recording time spent with oxygen saturation <90% (SpO2 < 90%), and mean oxygen desaturation (MeanSpO2%). Data were submitted for statistical analysis. The baseline values were AHI = 21.33 ± 14.79, supine AHI = 35.64 ± 12.80, ODI = 17.51 ± 13.5, SpO2 < 90% = 7.82 ± 17.08, and MeanSpO2% = 93.45 ± 1.86. Four patients had mild OSA (5 > AHI < 15), one moderate OSA (15 > AHI < 30), and three severe OSA (AHI > 30). After treatment with NOA®, statistically significant improvements in AHI (8.6 ± 4.21) and supine AHI (11.21 ± 7.26) were recorded. OrthoApnea NOA® could be an effective alternative in the treatment of OSA: the device improved the PSG parameters assessed.

A Narrative Review of the Association between Post-Traumatic Stress Disorder and Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) and post-traumatic stress disorder (PTSD) are often co-morbid with implications for disease severity and treatment outcomes. OSA prevalence is higher in PTSD sufferers than in the general population, with a likely bidirectional effect of the two illnesses. There is substantial evidence to support the role that disturbed sleep may play in the pathophysiology of PTSD. Sleep disturbance associated with OSA may interfere with normal rapid eye movement (REM) functioning and thus worsen nightmares and sleep-related movements. Conversely, hyperarousal and hypervigilance symptoms of PTSD may lower the arousal threshold and thus increase the frequency of sleep fragmentation related to obstructive events. Treating OSA not only improves OSA symptoms, but also nightmares and daytime symptoms of PTSD. Evidence suggests that positive airway pressure (PAP) therapy reduces PTSD symptoms in a dose-dependent fashion, but also presents challenges to tolerance in the PTSD population. Alternative OSA treatments may be better tolerated and effective for improving both OSA and PTSD. Further research avenues will be introduced as we seek a better understanding of this complex relationship.

Factors influencing adherence to oral appliance therapy in adults with obstructive sleep apnea: a systematic review and meta-analysis

STUDY OBJECTIVES

The review aimed to identify the factors influencing adherence to oral appliance therapy in adults with obstructive sleep apnea.

METHODS

The protocol was initially registered with the International Register of Systematic Reviews (Prospero: CRD42019122615) prior to undertaking a comprehensive electronic search of databases and references without language and date restrictions. Quality assessment was undertaken using the Cochrane Collaboration's risk of bias tool and Quality in Prognosis Studies (QUIPS) tool.

RESULTS

Studies exhibited low or unclear risk of bias for the domains assessed by the respective quality assessment tools. The influence of independent variables such as disease characteristics, patient characteristics, appliance features, and psychological and social factors on adherence levels was also assessed. There was a total of 31 included studies, which consisted of 8 randomized controlled trials, 2 controlled clinical trial, 7 prospective cohorts, 11 retrospective cohorts, and the remaining 3 studies were a case-series, case-control, and a mixed-methods. All 31 included studies were subject to qualitative analysis, with only 4 studies included in the quantitative analysis. Results of the meta-analysis demonstrated increased adherence with custom-made appliances, with a pooled mean difference of -1.34 (-2.02 to -0.66) and low levels of heterogeneity (I² = 0%).

CONCLUSIONS

A weak relationship was observed between objective adherence and patient and disease characteristics, such as age, sex, obesity, apnea-hypopnea index, and daytime sleepiness, to oral appliance therapy. Nonadherent patients reported more side effects with oral appliance therapy than users and tended to discontinue the treatment within the first 3 months. Custom-made oral appliances were preferred and increased adherence reported in comparison to ready-made appliances. Further research is imperative to examine the relationship between psychosocial factors and adherence to oral appliance therapy.

Mandibular advancement device use in obstructive sleep apnea: ORCADES study 5-year follow-up data

STUDY OBJECTIVES

Mandibular advancement devices (MADs) are an alternative to continuous positive airway pressure for the management of obstructive sleep apnea (OSA). The ORthèse d'avanCée mAndibulaire dans le traitement en DEuxième intention du SAHOS sévère (ORCADES) study is investigating the long-term effectiveness of MAD therapy in patients with OSA who refused or were intolerant of continuous positive airway pressure. Five-year follow-up data are presented.

METHODS

Data were available in 172 of 331 patients treated with a custom-made computer-aided design/computer-aided manufacturing biblock MAD (Narval CC; ResMed, Saint-Priest, France). The primary end point was treatment success (≥50% decrease in apnea-hypopnea index from baseline).

RESULTS

Five-year treatment success rates were 52% overall and 25%, 52%, and 63%, respectively, in patients with mild, moderate, or severe OSA. This reflects a decline over time vs 3-6 months (79% overall) and 2 years (68%). Rates declined in all patient subgroups but to the greatest extent in patients with mild OSA. The slight worsening of respiratory parameters over time was not associated with any relevant changes in sleepiness and symptoms. Moderate or severe OSA at baseline, treatment success at 3-6 months, and no previous continuous positive airway pressure use were significant independent predictors of 5-year treatment success on multivariate analysis. No new safety signals emerged during long-term follow-up. The proportion of patients using their MAD for ≥4 h/night on ≥4 days/wk was 93.3%; 91.3% of patients reported device use of ≥6 h/night at 5 years. At 5-year follow-up, 96.5% of patients reported that they wanted to continue MAD therapy.

CONCLUSIONS

Long-term MAD therapy remained effective after 5 years in >50% of patients, with good levels of patient satisfaction and adherence.

CITATION

Vecchierini MF, Attali V, Collet JM, et al. Mandibular advancement device use in obstructive sleep apnea: ORCADES study 5-year follow-up data. J Clin Sleep Med. 2021;17(8):1695-1705.

Predictive Factors for Efficacious Oral Appliance Therapy in Moderate to Severe Obstructive Sleep Apnea Patients

OBJECTIVES/HYPOTHESIS

Oral appliances (OAs) are a treatment for obstructive sleep apnea hypopnea syndrome (OSAHS). The main objective of the study was to determine the predictive factors of OA efficacy. The secondary objective was to measure the efficacy rates and determine OAs' tolerance and dropout.

STUDY DESIGN

Retrospective study.

METHODS

Efficacy results of the OAs based on the apnea hypopnea index (AHI) reduction, complications, and dropout rates were retrospectively collected from 347 patients with a moderate to severe OSAHS treated by a retention OA. The procedure was entirely performed by otolaryngologists.

RESULTS

The AHI with OA was more significantly reduced in patients with a higher initial AHI and a higher initial body mass index but reduction was not related to age and not proportional to the degree of mandibular advancement. The 50% AHI reduction rate after OA was 65.2%, the AHI ≤5/hr rate after OA was 26.1%, and the <50% AHI reduction and residual AHI > 10/hr rate was 50.1%. The OA significantly reduced the mean AHI (-14.9/hr, P < .0001). In 7.8% of patients, the AHI increased with OA. Seven patients (1.5%) experienced adverse effects. Thirty-seven (7.8%) patients stopped using OA mainly because of its ineffectiveness. Advancement can be considered beyond the initial maximal advancement. It can be effective sometimes; however, increasing advancement did not significantly reduce AHI.

CONCLUSIONS

OA is an effective and well-tolerated treatment for moderate to severe OSAHS. This treatment was effective for reduction of the AHI ≥50% in two-thirds of cases studied and it should be considered in more cases.

LEVEL OF EVIDENCE

4 Laryngoscope, 131:E2089-E2096, 2021.

What Do We Know About Adherence to Oral Appliances?

Long-term effective therapy is essential for obstructive sleep apnea (OSA) control and preventing comorbidity. OSA patients are often reported to be more receptive to oral appliance therapy over positive airway pressure (PAP). Oral appliance usage can now be objectively recorded by temperature microsensors. Studies using commercially available microsensor chips have reported data out to 1 year, with high rates of adherence (>80%), albeit in small samples. There is opportunity to further use this technology to understand individual adherence factors and patterns and in obtaining objective measures of treatment effectiveness, particularly for longer-term health outcomes and allowing comparison to PAP.

[Oral appliances for obstructive sleep apnoea: What can we expect?]

INTRODUCTION

Mandibular appliances are a treatment option for obstructive sleep apnea. There are many designs, but in the literature they tend to be grouped into a single entity without considering that efficiency, tolerance, compliance, or side effects are inherent in the design of each of them. A more detailed literature review is therefore warranted for the reader who wants to understand the relative effectiveness of each appliance.

STATE OF KNOWLEDGE

We conducted a literature search using the "oral appliance" and "obstructive sleep apnea" criteria on Pubmed, Embase and Cochrane. This allowed us to compare outcome parameters by appliance class and to highlight the rare studies comparing different appliances.

CONCLUSIONS

Mandibular appliances are not a homogeneous entity. Common use includes only appliances designed for propulsion (with rods and jacks) and retention. However, the few comparative studies available do not identify which are the most effective types or the types with an optimal efficacy/tolerance ratio.

PERSPECTIVES

Further appliance comparison studies are needed to determine the most effective type or with an optimal efficacy/tolerance ratio.

Oral Appliances in the Management of Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is a multifactorial condition, and an interdisciplinary approach to diagnosis forms the basis for effective treatment planning. Craniofacial structure and attached soft tissues and muscles play a central role in OSA. Evidence-based studies demonstrate the effectiveness of oral appliances for mandibular advancement and tongue stabilization in managing OSA, and current clinical standards of practice recommend the use of oral appliances to treat OSA when patients cannot tolerate continuous positive airway pressure (CPAP). Although effective, oral appliances are less predictable in managing OSA compared with CPAP therapy. Measures can be taken to improve predictability of oral appliance treatment.

Effect of mandibular advancement device on the stomatognathic system in patients with mild-to-moderate obstructive sleep apnoea-hypopnoea syndrome

Objective

This study was conducted to evaluate the changes of temporomandibular joints (TMJs) through magnetic resonance imaging (MRI) scanning and the electrical changes in mandibular movement and masticatory muscle surface of mild‐to‐moderate obstructive sleep apnoea‐hypopnoea syndrome (OSAHS) patients before and after treatment with mandibular advancement device (MAD).

Methods

This was a single‐centre, prospective study recruiting OSAHS patients undergoing treatment with MAD in Department of Stomatology, Yannan Hospital, Kunming, China. Patients were recruited from February 2015 to October 2015, and TMJ changes were observed in MRI scanning before and after 18 months of treatment with MAD in cohort 1. The second cohort of the patients were recruited from January 2014 to September 2015 and electrical changes in mandibular movement and masticatory muscle surface of patients before and after 6 months of treatment with MAD.

Results

In the cohort 1, TMJ changes analysed through MRI scanning, before and after 18‐month treatment with MAD, there was no significant deviation in the angle of joint disc position. A minor change in the position relationship between condylar process, articular disc and articular fossa but not significant was observed. There was no significant difference in the shape and magnitude of mandibular incision edge movement, percussion movement, masticatory movement and condylar central trajectory among the recruited OSAHS patients, before and after 6 months of MAD treatment as analysed through electromyography.

Conclusion

In this study, from the results it was evident that the effect of MAD on the stomatognathic system of OSAHS patients is minimal.

A Guide to Management of Sleepiness in ESKD

Daytime sleepiness, also known as hypersomnolence, is common among patients receiving maintenance dialysis and following successful kidney transplantation. Sleepiness may be secondary to medical comorbid conditions, medication side effect, insufficient sleep syndrome, and sleep-disordered breathing or the result of a primary central disorder of hypersomnolence, such as narcolepsy. Unrecognized and untreated sleep disorders are associated with substantial morbidity and mortality among patients with end-stage kidney disease. Effective management of hypersomnolence can improve quality of life in patients with kidney disease. This review focuses on the principal causes of sleepiness in patients with end-stage kidney disease. Awareness of these disorders by treating nephrologists is crucial. This review provides a systematic approach to guide providers through the recognition, early diagnosis, and treatment of hypersomnolence, which is commonly encountered in this patient population. Areas of future research are also suggested.

[OSA in adults: Role of the mandibular advancement device (MAD)]

Mandibular advancement devices are an alternative to continuous positive airway pressure for patients with mild or moderate obstructive sleep apnea/ hypopnea syndrome (OSA). Oral appliances advance the mandible and tongue, enlarge and stabilize the upper airways during sleep. Clinical examination is used to select candidates for oral appliances and a particular appliance for a given patient. Titration of the advancement will optimize its effectiveness by resolving subjective clinical symptoms. Polygraphic or ventilatory polysomnography controls the effectiveness of the treatment (IAH reduction, increase of oxygen saturation and improvement of the main symptoms). Clinical follow-up is required to assess longterm outcomes, side effects and treatment adherence. Oral appliances are effective in the short-term provided they achieved a 50% reduction in IAH and complete symptom resolution.

Efficacy and tolerability of a custom-made Narval mandibular repositioning device for the treatment of obstructive sleep apnea: ORCADES study 2-year follow-up data

OBJECTIVE/BACKGROUND

Mandibular repositioning device (MRD) therapy is an alternative to continuous positive airway pressure (CPAP). The Orkney Complex Disease Study-ORCADES study is assessing the long-term efficacy and tolerability of MRD therapy in obstructive sleep apnoea syndrome (OSAS); two-year follow-up data are presented.

PATIENTS/METHODS

OSAS patients who refused or were noncompliant with CPAP were fitted with a custom-made computer-aided design/computer-aided manufacturing (CAD/CAM) bi-block MRD (ResMed, Narval CC™); mandibular advancement was individually titrated. Sleep and respiratory parameters were determined at baseline, 3-6 months, and two years. The primary endpoint was treatment success (percentage of patients achieving a ≥50% reduction in the apnoea-hypopnoea index [AHI]).

RESULTS

Of 315 enrolled patients, 237 remained on MRD treatment at two years, and 197 had follow-up data. The treatment success rate at two years was 67%; AHI <5/h, <10/h and <15/h was achieved in 30%, 56% and 72% of patients, respectively. On multivariate analysis, ≥50% decrease in AHI at 3-6 months and absence of nocturia at 3-6 months were significant predictors of MRD treatment continuation. Adverse events were generally mild, and the majority occurred in the first year of treatment.

CONCLUSIONS

Two years' treatment with an MRD was effective and well tolerated in patients with mild to severe OSAS who refused or were intolerant of CPAP.

Oral Appliances in the Management of Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is a multifactorial condition, and an interdisciplinary approach to diagnosis forms the basis for effective treatment planning. Craniofacial structure and attached soft tissues and muscles play a central role in OSA. Evidence-based studies demonstrate the effectiveness of oral appliances for mandibular advancement and tongue stabilization in managing OSA, and current clinical standards of practice recommend the use of oral appliances to treat OSA when patients cannot tolerate continuous positive airway pressure (CPAP). Although effective, oral appliances are less predictable in managing OSA compared with CPAP therapy. Measures can be taken to improve predictability of oral appliance treatment.

Nocturia in Women With Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is underdiagnosed in women compared with men. Women have a tendency to underreport or present with atypical symptoms such as behavior changes, insomnia, fatigue, and depression. Nocturia, waking up from sleep 2 times or more to void, has been shown to be associated with OSA, but it is not an included symptom in commonly used screening questionnaires in primary provider offices. About 50% of patients with OSA have nocturia, and treatment of OSA improves it. Recognition of nocturia as a relevant symptom of OSA is important for primary providers to provide timely referral for the diagnosis of OSA.

Upper airway stabilization by osteopathic manipulation of the sphenopalatine ganglion versus sham manipulation in OSAS patients: a proof-of-concept, randomized, crossover, double-blind, controlled study

Background

Osteopathic manipulative treatment (OMT) of the sphenopalatine ganglion (SPG) is used empirically for the treatment of rhinitis and snoring and is thought to increase pharyngeal stability. This trial was designed to study the effects of this treatment on pharyngeal stability evaluated by critical closing pressure in obstructive sleep apnoea syndrome.

Methods

This single-centre, randomized, crossover, double-blind study compared active manipulation and sham manipulation of the SPG. Randomization was computer-generated. Patients each received one active manipulation and one sham manipulation at an interval of 21 days and were evaluated 30 min and 48 h after each session administered by a qualified osteopath. Neither the patients, nor the investigator performing the evaluations were informed about the order of the two techniques (double-blind). The primary endpoint was the percentage of responding patients presenting increased pharyngeal stability defined by a variation of critical closing pressure (Pcrit) of at least −4 cmH₂O at 30 min. Secondary endpoints were the variation of Pcrit in absolute values, sleepiness and snoring. Others endpoints were lacrimation (Schirmer’s test), induced pain, sensations experienced during OMT.

Results

Ten patients were included and nine (57 [50; 58] years, comprising 7 men, with an apnoea-hypopnoea index of 31.0 [25.5; 33.2]/h; (values are median [quartiles])) were analysed. Seven patients were analysed for the primary endpoint and nine patients were analysed for secondary endpoints. Five patients responded after active manipulation versus no patients after sham manipulation (p = 0.0209). Active manipulation induced more intense pain (p = 0.0089), increased lacrimation (ns) and more tactile, nociceptive and gustatory sensations (13 versus 1) compared to sham manipulation. No significant difference was observed for the other endpoints.

Conclusions

Osteopathic manipulative treatment of the SPG may improve pharyngeal stability in obstructive sleep apnoea syndrome. This trial validates the feasibility of the randomized, controlled, double-blind methodology for evaluation of this osteopathic treatment. Studies on a larger sample size must specify the efficacy on the apnoea-hypopnoea index.

Trial registration

The study was retrospectively registered in the clinicaltrial.gov registry under reference NCT01193738 on 1st September 2010 (first inclusion May 19, 2010).

Electronic supplementary material

The online version of this article (doi: 10.1186/s12906-017-2053-0) contains supplementary material, which is available to authorized users.