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MNT: Weight Management (2015)

Dixon J, Schachter L, O'Brien P, Jones K, Grima M, Lambert G, Brown W, Bailey M, Naughton M. Surgical vs conventional therapy for weight loss treatment of obstructive sleep apnea: a randomized controlled trial. JAMA. 2012; 308: 1,142-1,149 PubMed ID: 22990273
Study Design:
Randomized Controlled Trial
A - Click here for explanation of classification scheme.
Quality Rating:
Positive POSITIVE: See Quality Criteria Checklist below.
Research Purpose:
To determine whether surgically induced weight loss is more effective than conventional weight loss therapy in the management of Obstructive Sleep Apnea (OSA).
Inclusion Criteria:
Obese patients undergoing treatment at one of seven Melbourne, Australia, sleep clinics between September 2006 and March 2009 were recruited for the study. Of these, patients met the following inclusion criteria:
  • Aged 18 to 60 years
  • Body mass index of 35kg/m2 to 55kg/m2
  • Apnea-hypopnea index (AHI) of 20 events per hour or more, diagnosed within the previous six months, with a recommendation to commence continuous positive airway pressure (CPAP) therapy
  • At least three prior significant weight loss attempts.
Exclusion Criteria:
Subjects were excluded if there had been:
  • Previous bariatric surgery
  • Obesity hypoventilation syndrome requiring bi-level positive airway pressure
  • Contraindication to bariatric surgery including cognitive impairment
  • Drug or alcohol addiction
  • Significant cardiopulmonary neurological, vascular, gastrointestinal or neoplastic disease.
Description of Study Protocol:


Existing obese patients undergoing treatment at any of seven Melbourne, Australia, sleep clinics between September 2006 and March 2009 were invited to the study and asked to provide written informed consent.


  • Randomized controlled trial where patients were divided into two groups (conventional and surgical) through computer-derived randomization
  • Subjects were monitored from baseline to two years.

Blinding Used

  • Randomization achieved through computer-driven selection
  • All subjects were tested on same outcome parameters.


  • Conventional program participants were provided individualized dietary, physical activity and behavioral programs for weight loss by a dietitian and included an initial intensive very low-energy diet (VLED; e.g., Optifast) and ongoing follow-up and monitoring
  • Surgical program participants completed two weeks of VLED to reduce liver size prior to placement of laparoscopic adjustable gastric banding (LAGB; e.g., LAP-BAND System, Allergan Health) via the pars flaccida pathway within one month of randomization. Adjustment to band volume were made using standard clinical criteria.
  • Both programs had open access to a bariatric physician, a sleep physician and a dietitian. Progress was reviewed every four to six weeks for two years.

Statistical Analysis

  • Sample size selected to achieve statistical power of at least 80%
  • Univariate statistical analysis with SPSS statistical software, version 18 (SPSS Inc.)
  • Chi-square test
  • T-tests
  • Mann-Whitney tests
  • Multi-variate longitudinal analysis with PROC Mixed procedure in the SAS, version 9.2
  • Longitudinal models
  • Covariance structures to minimize corrected Akaike and Bayesian criteria
  • Person correlation coefficients
  • Confidence intervals with Fisher R-to-Z transformation
  • Two-sided P-value of 0.05 was considered statistically significant.
Data Collection Summary:

Timing of Measurements

Data was collected on each subject at their baseline, at each four- to six-week follow-up visit and at the end of two years. 

Dependent Variables

  • Change in apnea-hypopnea index (AHI), measured by diagnostic laboratyr polysomnography from baseline to two years
  • CPAP adherence, monitored by three monthly computerized downloads recording mean CPAP adherence (in hours) and pressure (in cm H20)
  • Sleep measures: Arousal index, percentages of rapid eye movement and slow wave sleep, mean and minimum oxygen saturation
  • Cardiovascular measures: Office blood pressure, resting heart rate, six-minute walk test,
  • Lipid levels of fasting plasma glucose, insulin, triglycerides, total and high-density lipoprotein cholesterol and calculated low-density lipoprotein cholesterol
  • Anthropometric measures of weight and waist, hip and neck circumference
  • Reported metabolic syndrome status
  • Epwoth Sleepiness Scale score (zero to 24)
  • Short Form 36 Health Survey
  • Beck Depression Inventory.

Independent Variables

  • Age
  • Sex
  • Gender.

Control Variables

The Non-Surgical Group served as the controls in this study.

Description of Actual Data Sample:
  • Initial N: 130 patients assessed for eligibility, but only 60 randomized (35 men, 25 women) between two groups
  • Attrition (final N): 54 (28 surgical, 26 conventional); 90% completion
  • Age: Surgical, 47.4±8.8 years; conventional, 50.0±8.2 years
  • Ethnicity: Not specified
  • Other relevant demographics: Comorbidities of hypertension, diabetes, depression and metabolic syndrome are noted and similar between groups
  • Anthropometrics monitored as described and similar between groups
  • Location: Australia.
Summary of Results:

Key Findings

  • The Surgical Group achieved a significantly greater mean weight loss of 27.8kg (95% CI, 20.9kg to 34.7kg) or a mean of 20.6% (95% CI, 15.4% to 25.7%) of initial body weight than the Conventional Group's 5.1kg (95% CI, 0.8kg to 9.3kg) or 2.9% (95% CI, 0.6% to 7.3%) at two years (P<0.001)
  • Both groups had a significant decrease in total apnea-hypoapnea index, with a decrease of 25.5 events per hour (95% CI, 14.2 to 36.7 events per hour) or 31.4% (95% CI, 12.7% to 50.2%) in the Surgical Group and 14.0 events per hour (95% CI, 3.3 to 24.6 events per hour) or 13.5% (95% CI, -5.8% to 32.9%) in the Conventional Group. The difference in reduction between groups was not significant.
  • CPAP usage and adherence declined in both groups, but was not significantly different between groups
  • Diabetics in the Surgical Group showed a significant change in hemoglobin A1C of -1.26% (95% CI, -1.97% to -0.55%; P=0.003).

Other Findings

  • There were no between-group differences in blood pressure, fasting glucose and insulin or plasma lipid profile
  • There were no within- or between-group differences in the use of anti-hypertensive, diabetes, lipid-lowering or anti-depressant medication.
Author Conclusion:
Comparing surgical and conventional weight loss therapy for the management of Obstructive Sleep Apnea (OSA) demonstrated greater weight loss in the Surgically Treated Group, however this did not translate into significantly greater improvements in OSA.
Funding Source:
University/Hospital: Monash University, Melbourne Australia
Reviewer Comments:
Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? Yes
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) Yes
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? Yes
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? Yes
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? Yes
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? Yes
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? Yes
5. Was blinding used to prevent introduction of bias? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? No
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) Yes
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? Yes
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? Yes
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? N/A
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? Yes
  6.6. Were extra or unplanned treatments described? Yes
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
  6.8. In diagnostic study, were details of test administration and replication sufficient? Yes
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? Yes
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? Yes
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? Yes
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes