Types of studies

We will include randomised controlled trials (RCTs) and quasi randomised trials regardless of blinding. We will include RCTs reported as full‐text in peer reviewed journals, those published as abstract only, and unpublished RCTs.

We will include studies where diagnosis is based on at‐home polysomnography or limited channel sleep study devices.

We will exclude studies where diagnosis of OSA is based on symptoms or questionnaires only.

Types of participants

We will include adult participants with OSA irrespective of the severity of the disease. We will use the diagnostic criteria of the AASM as the standard criteria for comparison purposes (Epstein 2009). If RDI and AHI are not available, we will consider an ODI between 5 and ess than 15 to be mild OSA, ODI between 15 and less than 30 to be moderate OSA, and ODI more than 30 to be severe OSA.

We will exclude children from this review, as data from surgery in this population have been studied elsewhere (Blackshaw 2014; Venekamp 2015).

Types of interventions

Treatment group: any specific surgical interventions for OSA (nasal surgeries, uvulopalatopharyngoplasty, tonsillectomy, palatal implant, tongue reduction, genioglossus advancement, radiofrequency ablation, maxillomandibular advancement, hyoid suspension, upper airway stimulation). We will exclude bariatric surgery, as this should be examined together with its common outcome, weight loss in a separate review.

Comparison group: other surgical or non‐surgical intervention, or no intervention/sham intervention.

Types of outcome measures

Electronic searches

We will identify studies from the Cochrane Airways Trials Register, which is maintained by the Information Specialist for the Group. The Cochrane Airways Trials Register contains studies identified from several sources:

1. monthly searches of the Cochrane Central Register of Controlled Trials (CENTRAL), through the Cochrane Register of Studies Online (crso.cochrane.org);

2. weekly searches of MEDLINE Ovid SP 1946 to date;

3. weekly searches of Embase Ovid SP 1974 to date;

4. Monthly searches of PsycINFO Ovid SP;

5. Monthly searches of CINAHL EBSCO (Cumulative Index to Nursing and Allied Health Literature);

6. Monthly searches of AMED EBSCO (Allied and Complementary Medicine);

7. handsearches of the proceedings of major respiratory conferences.

Studies contained in the Trials Register are identified through search strategies based on the scope of Cochrane Airways. Details of these strategies, as well as a list of handsearched conference proceedings are in Appendix 1. See Appendix 2 for search terms used to identify studies for this review.

We will search the following trials registries:

1. US National Institutes of Health Ongoing Trials Register, ClinicalTrials.gov (www.clinicaltrials.gov)

2. World Health Organization International Clinical Trials Registry Platform (apps.who.int/trialsearch)

We will search the Cochrane Airways Trials Register and additional sources from inception to present, with no restriction on language of publication.

Searching other resources

We will check reference lists of all primary studies and review articles for additional references. We will search relevant manufacturers' websites for trial information.

We will contact national sleep laboratories and experts in the fields of sleep and respiratory medicine, craniomaxillofacial (CMF) and ear, nose and throat (ENT) surgery to identify potentially relevant trials.

Selection of studies

Two review authors (SW and MP) will independently screen titles and abstracts for inclusion of all the potential studies we identify as a result of the search and code them as 'retrieve' (eligible or potentially eligible/unclear) or 'do not retrieve'. We will retrieve the full‐text study reports/publication and two review authors (SW, MP) will independently screen the full‐text and identify studies for inclusion, and identify and record reasons for exclusion of the ineligible studies. We will resolve any disagreement through discussion or, if required, we will consult a third person (IB). We will identify and exclude duplicates and collate multiple reports of the same study so that each study rather than each report is the unit of interest in the review. We will record the selection process in sufficient detail to complete a PRISMA flow diagram and 'Characteristics of excluded studies' table (Moher 2009).

Data extraction and management

Three reviewers (SW, MP and FS) will extract and check data. We will enter data into Review Manager 5 (RevMan 5) software (RevMan 2014). We will record data on treatment efficacy at the longest period of time post intervention reported in the studies. We will extract the following study characteristics.

1. Methods: study design, total duration of study, details of any 'run‐in' period, number of study centres and location, study setting, withdrawals, and date of study.

2. Participants: number (N), mean age, age range, gender, severity of condition, diagnostic criteria, baseline lung function, smoking history, inclusion criteria, and exclusion criteria.

3. Interventions: intervention, comparison, concomitant medications, and excluded medications.

4. Outcomes: primary and secondary outcomes specified and collected, and time points reported.

5. Notes: funding for trial, and notable conflicts of interest of trial authors.

We will resolve disagreements by consensus or by involving a fourth person (IB). One review author (SW) will transfer data into the RevMan 5 file (RevMan 2014). We will double‐check that data are entered correctly by comparing the data presented in the systematic review with the study reports. A second review author (IB) will spot‐check study characteristics for accuracy against the trial report.

Assessment of risk of bias in included studies

We will assess the risk of bias for each study using the criteria outlined in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2017). We will resolve any disagreements by discussion or by involving another author (IB). We will assess the risk of bias according to the following domains.

1. Random sequence generation

2. Allocation concealment

3. Blinding of outcome assessment (blinding of participants hardly possible)

4. Incomplete outcome data

5. Selective outcome reporting

6. Other bias

We will grade each potential source of bias as high, low or unclear and provide a quote from the study report together with a justification for our judgment in the 'Risk of bias' table. We will summarise the 'Risk of bias' judgements across different studies for each of the domains listed. We will consider blinding separately for different key outcomes where necessary (e.g. for unblinded outcome assessment, risk of bias for all‐cause mortality may be very different than for a patient‐reported pain scale). Where information on risk of bias relates to unpublished data or correspondence with a trialist, we will note this in the 'Risk of bias' table.

When considering treatment effects, we will take into account the risk of bias for the studies that contribute to that outcome.

Measures of treatment effect

We will use adjusted data if available, and if not, change from baseline, with final scores as third choice for continuous outcomes.

We will analyse dichotomous data as odds ratios and continuous data as mean difference or standardised mean difference. We will enter data presented as a scale with a consistent direction of effect.

We will undertake meta‐analyses only where this is meaningful, that is, if the treatments, participants and the underlying clinical question are similar enough for pooling to make sense.

We will narratively describe skewed data reported as medians and interquartile ranges.

Where multiple trial arms are reported in a single trial, we will include only the relevant arms. If two comparisons (e.g. surgery A versus placebo and surgery B versus placebo) are combined in the same meta‐analysis, we will halve the control group to avoid double‐counting.

Unit of analysis issues

The unit of analysis will be the participant.

Dealing with missing data

We will contact investigators or study sponsors in order to verify key study characteristics and obtain missing numerical outcome data where possible (e.g. when a study is identified as abstract only). Where this is not possible, and the missing data are thought to introduce serious bias, we will explore the impact of including such studies in the overall assessment of results by a sensitivity analysis. 

Assessment of heterogeneity

We will use the I² statistic (Higgins 2003) to measure heterogeneity among the trials in each analysis. If we identify substantial heterogeneity we will report it and explore possible causes by prespecified subgroup analysis. 

Assessment of reporting biases

If we are able to pool more than 10 trials addressing similar surgeries, we will create and examine a funnel plot to explore possible small study and publication biases.

Data synthesis

We will use a random‐effects model and perform a sensitivity analysis with a fixed‐effect model.

Subgroup analysis and investigation of heterogeneity

We plan to carry out the following subgroup analyses.

1. Mild versus moderate versus severe OSA

2. Body weight (obese versus non‐obese)

We will use the following outcomes in subgroup analyses.

1. Apnoea Hypopnoea Index (AHI)

2. Epworth Sleepiness Score (ESS)

3. Long‐term stability (after 12 months or more)

4. Quality of life

5. Permanent or reversible adverse effects

We will use the formal test for subgroup interactions in RevMan 5 (RevMan 2014).

Sensitivity analysis

We will conduct a sensitivity analysis focusing on RCTs with low risk of bias, and sensitivity analyses making plausible assumptions for missing data (Akl 2013; Ebrahim 2013).