NCBS: Weight Loss and Weight Regain Expected After Procedure (2009)
The purpose was to evaluate long-term results of Roux-en-Y gastric bypass surgery (RYGBP) and horizontal gastroplasty surgeries.
Operated on for morbid obesity between 1976 and 1986 at the Department of Surgery, University of Erlangen.
- No bariatric surgery at this hospital
- Bariatric surgery at other places.
- 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.
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).
- 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.
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 |
- 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.
Other: | funding source not specified |
Quality Criteria Checklist: Primary Research
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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 | |