NCBS: Weight Loss and Weight Regain Expected After Procedure (2009)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

The purpose was to evaluate long-term results of Roux-en-Y gastric bypass surgery (RYGBP) and horizontal gastroplasty surgeries.

Inclusion Criteria:

Operated on for morbid obesity between 1976 and 1986 at the Department of Surgery, University of Erlangen.

Exclusion Criteria:
  • No bariatric surgery at this hospital
  • Bariatric surgery at other places.
Description of Study Protocol:
  • Recruitment: Out of a potential 195 patients, adequate follow-up data were available for 90 
  • Design: Retrospective cohort study 
  • Intervention: RYGBP or horizontal gastroplasty bariatric surgery.

Statistical Analysis

  • Non-parametric Wilcoxson sign-ranked test to assess significance of differences between zero time and other end points
  • Wilcoxson-Mann-Whitney test for two sample problems
  • Kruskall-Wallis test for multiple sample problems
  • Cochran-Armitage test for categorical variables
  • McNemar test to infer about existence of side effects before surgery
  • Linear model for multivariate analyses (although doubts about normality of data present)
  • P<0.05 indicated significance.

 

Data Collection Summary:

Timing of Measurements

Percent of excess weight loss (EWL) measured at three, six, 12, 24 and 36 months; 10,15, 20 and anything over 22.5 years, labeled as 25 years.

Dependent Variables

Percent excess weight loss (% EWL).

Independent Variables

Type of surgery (horizontal gastroplasty, stapled gastric bypass or transected gastric bypass).

 

 

Description of Actual Data Sample:

 

  • Initial N: 98 of 195 patients available for follow-up 23 years after surgery (82 women, 16 men)
  • Attrition: 50% of patients lost to follow-up over the 23 years
  • Age: Mean age at surgery, 31.8 years; mean length of follow-up, 22.9 years
  • Ethnicity: Not described (likely German)
  • Other relevant demographics: No difference as to demographics in the original study group and patients available to follow-up
  • Anthropometrics: No differences in BMI before surgery by operation type (mean BMI at surgery, 46.6kg/m2)
  • Location: Germany.
Summary of Results:

 

Variables

Horizontal Gastroplasty

S-RYGBP

T-RYGBP

Wilcoxon Test between HGP and RBGBP 

P-value

One year, % EWL

-3.3 % (N=17)

59.2% (N=11)

49.1% (N=40)

 0.0135

Two years, % EWL

 -14.8% (N=8)

 61.5% (N=10)

 51.9 % (N=37)

 0.0079

Three years, % EWL

-14.8 (N=8)

 55.9 (N=10)

 51.7% (N=42)

 0.1056

10 years, % EWL -13.8 (N=16) 33.5% (N=14) 38.7% (N=58)  0.0005
15 years, % EWL -12.3 (N=16) 33.7% (N=12) 28.0 (N=57)  0.0130
20 years, % EWL -10.4 (N=18) 31.8% (N=13) 29.9% (N=53)  0.0034
25 years, % EWL 7.9 (N=2) 31.1% (N=8) 27.5% (N=62)  0.5066

 

 

Author Conclusion:
  • HGP most ineffective method
  • No difference in S-RYGBP or T-RYGBP
  • Recommend laparoscopic T-RYGBP with lesser curvature pouch of 15mL to 25mL and 21 to 25 circular gastrojejunostomy
  • Gender did not influence results.
Funding Source:
Other: funding source not specified
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.) No
  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")? N/A
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? N/A
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? N/A
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? N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  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? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? N/A
  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? N/A
  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)? No
  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? N/A
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