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:
  • To examine trends and effects of weight loss treatment on health-related quality of life (HRQL) in severely obese patients over 10 years (post-surgery or post-conventional treatment)
  • The specific purpose of this study is to detemine if long-term weight reduction is associated with long-standing improvement in HRQL and to evaluate the implications of weight regain on HRQL.
Inclusion Criteria:
  • A cluster of 1703 consecutive subjects were gleaned from the large data set of the SOS intervention study from 1987 to 1994
  • A complete data base (using the HRQL records) at 10-years follow-up were used for this analysis.
Exclusion Criteria:
  • Subjects who were out of the range of subjects (from the 1987 to 1994 data set) were excluded. The larger data set included the entire SOS registry, an ongoing nationwide project (SOS).  
  • Subjects with incomplete information on the HRQL battery of tests were excluded.
Description of Study Protocol:

Recruitment

  • Advertisements in the media and through information to primary health care centers
  • The subjects were recruited through invitation and personal interest, not surgeon referral.

Design

  • The SOS "master" study is an ongoing nationwide project; a cross-sectional (registry), longitudinal, intervention trial of obese subjects
  • There are several subsets to the master SOS study. This research focuses on a smaller, convenience sample or consecutive set of subjects gleaned from the 1987 to 1994 records. Only subjects with complete data on the HRQL were included in this group.

Blinding Used

Not applicable.

Intervention

Weight loss by surgical intervention vs. conventional treatment for lifestyle change and weight reduction.

Statistical Analysis

  • Fisher's nonparametric permutation tests were performed for difference testing
  • For comparison of three or more groups, the nonparametric ANOVA test and the Tukey range test was used for post hoc testing of differences among mean values
  • Correlations between variables were tested using Pitman's nonparametric permutation test and Pearson's correlation coefficients were calculated for descriptive purposes
  • The limit for significance was set at the 5% level. 

 

Data Collection Summary:
  • Timing of measurements: Mail-out/mail-back questionnaires at 0.5, one, two, three, four, six, eight, 10, 15 and 20 years of follow-up after the treatments had been chosen and started 
  • Dependent variables: HRQL index and weight loss achieved
  • Independent variables: Surgical intervention for obesity treatment vs. conventional treatment for lifestyle change and weight reduction.
Description of Actual Data Sample:
  • Initial N: 1276 subjects (655 of the 851 surgical care; 621 of the 852 conventional care subjects were included in this analysis) 
  • Attrition (final N): About 75% had complete data sets for the HRQL component of study
  • Age: 47±5.7 years for the surgical group; 48.4±6.7 years in the conventional treatment group
  • Ethnicity: Northern Europeans, Sweden
  • Other relevant demographics: None provided
  • Anthropometrics: In the original population group from the SOS study the BMI criteria was 34kg per m2 or more for men and 38kg per m2 or more for women
  • Location: Goteborg Sweden; Sahlgrenska Academy at Goteborg, Sweden.

 

Summary of Results:

Findings - HRQL Index

  • The Health-related quality of life (HRQL) index fluctuated with weight loss, weight regain and weight stabilization 
  • HRQL improvements were noted for the surgical group one-year post-surgery. This was followed by a weight regain stage (one to six years) post-surgery and an accompanying decline in HRQL. The period from six to 10 years was characterized by stability in both weight and HRQL scores. The HRQL score was higher at the 10-year mark compared to baseline. 
  • The HRQL index in the conventional group followed a different trend. The conventional group subjects had small initial improvements in HRQL scoring, but most of the small improvements were lost within two years. However, some of the HRQL sub-scores improved at the end of the 10-year study. The long-term outcome for the HRQL indexes was mixed. 

Weight Loss After Ten Years

  • About 66% of the surgical subjects were able to maintain a loss of 10% or more of their body weight over a 10-year timeframe. This weight loss achievement was capable of producing an improved HRQL score among the subjects in this study. 
  • Overall, the weight loss achieved was greatest in the surgical subjects who had the gastric bypass procedures (25%), compared to the banding or stomach restricting procedures  
  • Even though HRQL scoring is variable and fluctuates over time, it is safe to state that when weight loss is achieved, HRQL improves.

Weight Loss Achievements

  • Surgically treated group mean BMI 10-year weight loss: 35.3±5.4kg per m2 or -6.7±5.4kg per m2 
  • Conventionally treated group mean BMI 10-year weight gain: 40.6 ±5.9kg per m2 or a +0.7±4.9kg per m2.  
Author Conclusion:
  • Long-lasting weight reduction in the obese population has a general long-standing positive outcome on HRQL scoring. Improvements during follow-up, during the 10-year observation period were generally associated with the magnitude of weight loss. The more weight lost, the better the HRQL score. 
  • Weight loss of 10% that is sustained improves HRQL scoring. Thus, bariatric surgery is a favorable option for the treatment of severe obesity. 
Funding Source:
Government: Swedish Research Council
University/Hospital: Grotborg Univesity (Sweden)
Not-for-profit
0
Reviewer Comments:
  • This study focuses on mental well-being via a HRQL score 
  • The components of the HRQL index include current health perception, social interaction, obesity-problems, overall mood, depression and anxiety.

 

 

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.) Yes
  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? Yes
  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? Yes
  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? N/A
  6.6. Were extra or unplanned treatments described? N/A
  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? 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? 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