Otherindependent cross-checkabstract checked I-PPI-115 standard review
More pneumonia during periods of PPI use
Proton pump inhibitor use and risk of pneumonia: a self-controlled case series study.
Overview
Maret-Ouda J et al.. J Gastroenterol 2023 · PMID 37314495 · DOI 10.1007/s00535-023-02007-5
In Sweden, people had 73% more pneumonia episodes during times they took PPIs than during times they did not.
Does the study support the specific claim? Yes · Methodological quality: moderate
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Test PPIs and pneumonia within the same people.
- How was the study done?
Self-controlled case series.
- How many people, animals or samples were studied?
519,152 patients.
- What was actually found?
IRR 1.73; H2RA 1.08.
- How large was the observed effect?
1.73 (1.71-1.75).
- What do the results mean in everyday life?
Pneumonia risk may rise during PPI use.
- What are the study's limitations?
Possible bias from timing of prescriptions.
- What does it say about Elawady's specific claim?
Supports the pneumonia association.
- Do the results apply to Germany and Europe?
Swedish data.
- What can explicitly not be concluded from this study?
Cannot prove causation.
Scientific in-depth review
1. Full reference
- Authors
- Maret-Ouda J et al.
- Journal
- J Gastroenterol
- Year
- 2023
- Identifier
- PMID 37314495 DOI 10.1007/s00535-023-02007-5
- Verification
- verified – PubMed efetch 2026-10-26 + Crossref 2026-10-26
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
Swedish Research Council; no conflicts declared
2. Research question
Does PPI use increase pneumonia risk within individuals?
3. Study design and population
- Study design
- Other – Nationwide self-controlled case series
- Population
Swedish patients with >=1 pneumonia episode
- Country
Sweden
- Period
2005-2019
- Sample size
519,152 patients; 307,709 PPI periods
- Inclusion and exclusion criteria
People with pneumonia in national registers
4. Methods and endpoints
- Exposure / intervention
PPI-exposed periods
- Comparator
Unexposed periods in the same person
- Endpoints
Pneumonia
- Statistical methods
Conditional fixed-effect Poisson regression (IRR)
5. Actual results
- Results
IRR 1.73 (1.71-1.75) during PPI use; H2RA IRR 1.08 (1.02-1.14).
- Absolute risks
Not reported
- Authors' conclusion
PPI use seems associated with increased pneumonia risk; caution in people with prior pneumonia.
6. Strengths
- Controls for fixed between-person confounding
- H2RA comparison
7. Weaknesses
- Time-varying confounding (prodromal symptoms, aspiration) possible
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
SCCS assumptions may be violated if pneumonia affects PPI exposure.
9. Assessment of the statistical interpretation
Precise but possibly biased; inconsistent with RCT estimates (stats/C-PPI-05_pneumonia.py).
10. Relevance to the specific claim
Strongest recent observational support for the pneumonia part.
11. Independent contrary findings
RCT meta-analyses (I-PPI-113, I-PPI-114).
12. Transferability to Germany and Europe
Directly applicable.
13. Overall methodological judgement
Supports association; causality disputed.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | some concerns |
| Precision of results | high |
| Directness | direct |
| Reproducibility | partly replicated |
| Consistency with the overall evidence | inconsistent |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Why RCTs and SCCS disagree.
15. Linked fact checks
- Long-term acid suppression causes hip fractures and pneumonia. – Studies supporting the claim