Cohort studycited by the Tayebat archiveabstract only checked A-BAR-02 standard review
Swedish study: fewer deaths after weight-loss surgery
Effects of bariatric surgery on mortality in Swedish obese subjects.
Overview
Sjöström L et al.. N Engl J Med 2007 · PMID 17715408 · DOI 10.1056/NEJMoa066254
Over about 11 years, people who had surgery had roughly 24-29% lower risk of dying than matched controls.
Does the study support the specific claim? No · Methodological quality: moderate
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Test mortality effect
- How was the study done?
Prospective matched study
- How many people, animals or samples were studied?
4047 adults
- What was actually found?
Fewer deaths after surgery
- How large was the observed effect?
Adjusted HR 0.71
- What do the results mean in everyday life?
Surgery was linked to living longer
- What are the study's limitations?
Not randomized; older techniques
- What does it say about Elawady's specific claim?
Argues against 'surgery kills'
- Do the results apply to Germany and Europe?
Directly European
- What can explicitly not be concluded from this study?
Exact causal size
Scientific in-depth review
1. Full reference
- Authors
- Sjöström L, Narbro K, Sjöström CD, Karason K, Larsson B, Wedel H, Lystig T, Sullivan M, Bouchard C, Carlsson B, Bengtsson C, Dahlgren S, Gummesson A, Jacobson P, Karlsson J, Lindroos AK, Lönroth H, Näslund I, Olbers T, Stenlöf K, Torgerson J, Agren G, Carlsson LM, Swedish Obese Subjects Study
- Journal
- N Engl J Med
- Year
- 2007
- Identifier
- PMID 17715408 DOI 10.1056/NEJMoa066254
- Verification
- verified – PubMed E-utilities efetch, 2026-10-25
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
COI: not stated in record | Grants: Medical Research Council
2. Research question
Does bariatric surgery reduce overall mortality compared with conventional treatment?
3. Study design and population
- Study design
- Cohort study – Prospective controlled (non-randomized) intervention study, Swedish Obese Subjects (SOS)
- Population
Adults with obesity in Sweden
- Country
Sweden
- Period
Recruitment 1987-2001; analysis Nov 2005
- Sample size
4047 (2010 surgery, 2037 matched controls)
- Inclusion and exclusion criteria
Matched on multiple risk factors; surgery chosen by patients (no randomization)
4. Methods and endpoints
- Exposure / intervention
Gastric bypass, vertical-banded gastroplasty, banding
- Comparator
Conventional obesity treatment
- Endpoints
Overall mortality
- Statistical methods
Cox regression, unadjusted and adjusted
5. Actual results
- Results
129 deaths control vs 101 surgery; unadjusted HR 0.76 (P=0.04); adjusted HR 0.71 (P=0.01). Weight loss at 10 years 25% (bypass), 16% (VBG), 14% (banding); controls within +/-2%.
- Absolute risks
Deaths 101/2010 vs 129/2037 over mean 10.9 years
- Authors' conclusion
Bariatric surgery for severe obesity is associated with long-term weight loss and decreased overall mortality.
6. Strengths
- Prospective with matched controls
- 99.9% vital status follow-up
7. Weaknesses
- Not randomized (self-selection)
- Mostly older procedures (VBG, banding); few bypass, no sleeve
8. Risk of bias
- Orienting tool
- ROBINS-E
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- some concerns
- Rationale
Confounding by indication/selection possible despite matching.
9. Assessment of the statistical interpretation
Relative risk reduction about 24-29%; absolute difference modest over 11 years.
10. Relevance to the specific claim
Contradicts the claim that bariatric surgery is lethal or shortens life.
11. Independent contrary findings
Replicated by Adams 2007 (A-BAR-03), SOS 2020 (A-BAR-05), meta-analysis I-BAR-01.
12. Transferability to Germany and Europe
Directly European.
13. Overall methodological judgement
Important, consistent evidence for a mortality benefit in severe obesity; non-randomized.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | some concerns |
| Precision of results | moderate |
| Directness | indirect |
| Reproducibility | replicated |
| Consistency with the overall evidence | consistent |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Effect of current procedures (sleeve) not covered.
15. Linked fact checks
- Sleeve gastrectomy (and bariatric surgery in general) is a lethal operation that kills patients / shortens life. – Studies contradicting or limiting the claim
- Sleeve gastrectomy makes cancer appear decades earlier (it 'kills' and brings cancer forward). – Studies contradicting or limiting the claim
Use by the Tayebat archive
Note: according to the archive, the studies were compiled by the archive operators. Whether Dr. Elawady himself cited this study is not established.
- What the archive says about the study
Listed in the archive bibliography only; the archive gives no specific interpretation.
- A. What was actually studied?
Mortality after surgery vs usual care
- B. What did the authors find?
Lower mortality after surgery (adjusted HR 0.71)
- C. What conclusions do the authors themselves draw?
Surgery associated with decreased mortality
- D. What does the archive derive from it?
None explicit.
- E. Is this derivation scientifically justified?
Not applicable; the study contradicts claims that surgery shortens life.
- Adequacy of the interpretation (by the archive)
- not applicable