Cohort studyindependent cross-checkabstract checked★ key study I-BAR-138 in-depth review
Swedish study: bowel inflammation after obesity surgery
The risk of inflammatory bowel disease after bariatric surgery.
Overview
Kiasat et al.. Surg Obes Relat Dis 2022 · PMID 35012883 · DOI 10.1016/j.soard.2021.12.014
Ulcerative colitis was diagnosed more often after sleeve (and Crohn disease after bypass) than in the general population.
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?
IBD after surgery
- How was the study done?
Register cohort
- How many people, animals or samples were studied?
698,718
- What was actually found?
SG: UC HR 1.8
- How large was the observed effect?
HR 1.8
- What do the results mean in everyday life?
A possible, small link with bowel inflammation
- What are the study's limitations?
Controls not obese
- What does it say about Elawady's specific claim?
Partly supports immune-disease claim (IBD only)
- Do the results apply to Germany and Europe?
Directly European
- What can explicitly not be concluded from this study?
Causation
Scientific in-depth review
1. Full reference
- Authors
- Kiasat et al.
- Journal
- Surg Obes Relat Dis
- Year
- 2022
- Identifier
- PMID 35012883 DOI 10.1016/j.soard.2021.12.014
- 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 bariatric surgery associated with new-onset inflammatory bowel disease?
3. Study design and population
- Study design
- Cohort study – Nationwide register-based cohort (SOReg) with general-population controls (1:10)
- Population
Swedish adults with primary RYGB or SG 2007-2018 and matched general-population controls
- Country
Sweden
- Period
2007-2019
- Sample size
64,188 operated; 634,530 controls
- Inclusion and exclusion criteria
Matched on age, sex, region
4. Methods and endpoints
- Exposure / intervention
RYGB or SG
- Comparator
General-population controls (not obese-matched)
- Endpoints
Crohn's disease, ulcerative colitis, unclassified IBD
- Statistical methods
Cox regression
5. Actual results
- Results
RYGB: Crohn's HR 1.8 (1.5-2.2), IBD-unclassified HR 2.7 (2.0-3.7), UC HR 0.9 (0.8-1.1). SG: UC HR 1.8 (1.1-3.1); Crohn's HR 0.8 (0.3-2.1); IBD-unclassified HR 2.5 (0.8-7.8).
- Absolute risks
not reported in abstract
- Authors' conclusion
RYGB associated with increased Crohn's and unclassified IBD; SG associated with increased UC only.
6. Strengths
- Nationwide, large
7. Weaknesses
- Controls not matched for obesity (obesity itself may raise IBD risk)
- Surveillance bias after surgery (more endoscopy)
8. Risk of bias
- Orienting tool
- ROBINS-E
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- high
- Rationale
Confounding by obesity and detection bias.
9. Assessment of the statistical interpretation
SG UC CI 1.1-3.1 fairly wide.
10. Relevance to the specific claim
Supports an association between sleeve and ulcerative colitis (an immune-mediated disease), not proof of causation.
11. Independent contrary findings
Comparator is general population, not people with obesity.
12. Transferability to Germany and Europe
Swedish.
13. Overall methodological judgement
Real signal for IBD, causality unproven.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | high |
| Precision of results | moderate |
| Directness | direct |
| Reproducibility | partly replicated |
| Consistency with the overall evidence | mixed |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Mechanism; obese-matched comparisons.
15. Linked fact checks
- Sleeve gastrectomy causes autoimmune diseases and fibromyalgia. – Studies with mixed or unclear results