Cohort studyindependent cross-checkabstract checked★ key study I-BAR-104 in-depth review
Nordic study: survival after obesity surgery
Effects of Obesity Surgery on Overall and Disease-Specific Mortality in a 5-Country Population-Based Study.
Overview
Kauppila et al.. Gastroenterology 2019 · PMID 30940524 · DOI 10.1053/j.gastro.2019.03.048
Operated people died less often than non-operated people with obesity, but more often than the general population; suicide deaths were more frequent.
Does the study support the specific claim? Partly · Methodological quality: moderate
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Compare survival with two reference groups
- How was the study done?
Registry cohort
- How many people, animals or samples were studied?
505,258 (49,977 operated)
- What was actually found?
HR 0.63 vs obese; SMR 1.94 vs general population
- How large was the observed effect?
All-cause HR 0.63; suicide HR 1.68
- What do the results mean in everyday life?
Surgery reduces but does not remove the excess risk of obesity
- What are the study's limitations?
Older procedures; registry data
- What does it say about Elawady's specific claim?
Contradicts "lethal", supports "still shorter life than general population"
- Do the results apply to Germany and Europe?
Direct European data
- What can explicitly not be concluded from this study?
Sleeve-specific long-term effects
Scientific in-depth review
1. Full reference
- Authors
- Kauppila et al.
- Journal
- Gastroenterology
- Year
- 2019
- Identifier
- PMID 30940524 DOI 10.1053/j.gastro.2019.03.048
- Verification
- verified – PubMed efetch 2026-10-26 + Crossref API
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
not stated in abstract
2. Research question
Is survival after bariatric surgery similar to the general population and longer than in non-operated people with obesity?
3. Study design and population
- Study design
- Cohort study – Population-based registry cohort from 5 Nordic countries
- Population
Persons with an obesity diagnosis in Nordic national registries, 1980-2012
- Country
Denmark, Finland, Iceland, Norway, Sweden
- Period
1980-2012
- Sample size
505,258 (49,977 operated)
- Inclusion and exclusion criteria
Obesity diagnosis in nationwide registries
4. Methods and endpoints
- Exposure / intervention
Bariatric surgery (mostly gastric bypass and older procedures)
- Comparator
Non-operated obese persons; general population (SMR)
- Endpoints
All-cause, CVD, diabetes, cancer and suicide mortality
- Statistical methods
Poisson SMRs; multivariable Cox regression
5. Actual results
- Results
All-cause SMR after surgery 1.94 (1.83-2.05), rising to 2.28 (2.07-2.51) at >=15 y; non-operated obese SMR 2.15 (2.11-2.20). Surgery vs non-operated: all-cause HR 0.63 (0.60-0.66); CVD 0.57 (0.52-0.63); diabetes 0.38 (0.29-0.49); suicide HR 1.68 (1.32-2.14); cancer mortality HR 0.84 (0.76-0.93) overall but 1.20 (1.02-1.42) at >=15 y.
- Absolute risks
not reported in abstract
- Authors' conclusion
Operated patients live longer than non-operated obese individuals, but their mortality remains higher than in the general population and increases with time.
6. Strengths
- Nationwide, very large, long follow-up
- Two reference groups (general population and obese non-operated)
7. Weaknesses
- Registry diagnosis of obesity (selection)
- Few sleeve operations in 1980-2012
- Limited confounder data
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; obesity diagnosis only in contact with health care.
9. Assessment of the statistical interpretation
CI log-symmetric (stats/I-BAR-104_kauppila_2019.py). SMR vs general population and HR vs obese controls answer different questions.
10. Relevance to the specific claim
Shows both sides: lower overall mortality vs obese controls, and real excess suicide and late cancer-mortality signals; explains the "5.5 years" gap in C-BAR-09.
11. Independent contrary findings
Mostly older procedures; indirect for sleeve.
12. Transferability to Germany and Europe
Nordic data directly European.
13. Overall methodological judgement
Large, balanced evidence: overall benefit with specific late risks.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | some concerns |
| Precision of results | high |
| 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
Whether the late cancer-mortality signal applies to sleeve.
15. Linked fact checks
- Sleeve gastrectomy (and bariatric surgery in general) is a lethal operation that kills patients / shortens life. – Studies with mixed or unclear results
- Even the largest long-term study (SOS) showed that surgery patients still die 5.5 years earlier than the general population. – Studies supporting the claim
- Sleeve gastrectomy makes cancer appear decades earlier (it 'kills' and brings cancer forward). – Studies with mixed or unclear results
- Bariatric surgery is followed by documented rises in self-harm, suicide-related deaths and alcohol use disorder. – Studies supporting the claim