EAL

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 determine the effects of bariatric surgery vs. conventional weight loss therapy on mortality data extended over an average of 10.9 years of follow-up.

Inclusion Criteria:

Age 37 to 60 years
Body mass index (BMI) of 34kg per m² or more for men and 38kg per m²or more for women
Health considerations were liberal, but any stroke or myocardial infarction (MI) had to occur more than six months prior to surgery.

Exclusion Criteria:

Inappropriate age (less than 37 years or more than 60 years)
Inappropriate BMI for gender (less than 34kg per m²for men or less than 38kg per m² for women)
Additionally, the authors referenced a previously published study that detailed additional exclusion criteria: (Sjostrom, Larsson, Backman et al. Swedish Obese Subjects: Recruitment for an intervention study and a selected description of the obese state. Int. J. of Obes Relat Metab. Disord. 1992; 16; 465-479.)

Description of Study Protocol:

Recruitment

Patients from 25 surgical centers and 480 primary health care facilities were recruited and informed about the study
Seven regional ethics review boards approved the study protocol.

Design

Nonrandomized trial, prospective, longitudinal study with surgical patients and matched controls (conventional lifestyle modification).

Blinding Used

None.

Intervention

Three bariatric surgical procedures

Nonadjustable or adjustable banding procedure
Gastric bypass
Vertical banded gastroplasty (VBG).

Statistical Analysis

Mean values with standard deviations or 95% confidence intervals were used to describe the baseline characteristics and changes over time in the two study groups
Estimated hazard ratios for a proportional hazards model were also reported and calculated.

Data Collection Summary:

Timing of Measurements

At baseline (four weeks prior to surgery)
The intervention day was the day when the surgery occurred
All subsequent examinations and questionnaires were completed at 6 months and year one, two, three, four, six, eight, 10 and 15 in both study groups.

Dependent Variables

Mortality data and information on disease incidence
Weight loss.

Independent Variables

Surgical procedures (gastric bypass, VBG and banding).

Control Variables

All the subjects were middle-aged, obese individuals enrolled in the Swedish Obese Subject (SOS) study
All the subjects completed multiple questionnaires over multiple and extended periods of time.

Description of Actual Data Sample:

Initial N: 4047 participants (2010 had bariatric surgery and 2037 were matched for lifestyle interventions)
Attrition (final N):
- The study is ongoing (longitudinal). The follow-up rate regarding vital status is 99.9%
- For the questionnaires and other follow-up data the exams at the second, tenth and fifteenth years are 94%, 84% and 66%, respectively
- For the corresponding exams for the control group it was: 83%, 75%, and 87%, respectively.
Age: 37 to 60 years
Ethnicity: Swedish citizens, Northern European residents
Other relevant demographics:
- 590 men and 1420 women in the surgical group
- 590 men and 1447 women in the control group
Anthropometrics: At baseline the subjects in the surgical group had a BMI of 42.4±4.5kg per m² and the subjects in the control group had a BMI of 40.1±4.7kg per m². Thus, the control group subjects were lighter in weight compared to the surgical subjects.
Location: Multiple locations throughout Sweden.

Summary of Results:

Mortality Findings

129 subjects died in the control group and only 101 subjects died in the surgical group during the designated 10-year follow-up period
Immediately after surgery (within the first 90 days), there were five deaths in the surgical group due to peritonitis with organ failure and one because of sudden death. There were two deaths in the same time period in the control group; one from alcohol-related causes and one from cancer of the pancreas.
There were 53 deaths from cardiovascular conditions in the control group and 43 cardiovascular deaths in the surgical group. There were 76 deaths from all other conditions among the control group subjects and 58 deaths from various conditions in the surgical group.
The unadjusted overall hazard ratio was 0.76 in the surgery group (P=0.04) as compared with the control group. Overall mortality was higher in subjects who had had cardiovascular events before baseline than the subjects without such events.

Weight Loss

Maximal weight loss occurred in the surgical subjects
The maximum loss was observed after one to two years post-surgery, with the gastric bypass patients experiencing the greatest weight loss at 32%, the VBG patients at 25% loss and the other banded patients at 20% loss.

**Weight Loss Status by Year of Follow-up**
	Mean Percent Weight Change (N)
Treatment	2 years	10 years	15 years
Bypass surgery	32±8% (245)	25±11% (58)	27±12% (10)
Vertical-banded gastroplasty	25±9% (1244)	16±11% (746)	18±11% (108)
Banding	20±10% (357)	14±14% (237)	13±14% (52)
Control	±2% baseline (1660)	±2% baseline (886)	±2% baseline (190)

Author Conclusion:

This research report indicated that bariatric surgery was associated with a reduction in overall mortality, suggesting that it may be a favorable option for treating severe obesity.

Funding Source:

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?	N/A
	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")?	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?		No
	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.)	No
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	No
	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?	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?	???
	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