Meta-analysisindependent cross-checkabstract checked I-ABX-115 standard review
Infant antibiotics linked to childhood asthma, less so after accounting for bias
Association of infant antibiotic exposure and risk of childhood asthma: A meta-analysis.
Overview
Zhang Z et al.. World Allergy Organ J 2021 · PMID 34934469 · DOI 10.1016/j.waojou.2021.100607
Pooled data: about 37% higher odds, 19% when bias is addressed.
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?
Pool studies on infant antibiotics and asthma
- How was the study done?
Meta-analysis
- How many people, animals or samples were studied?
52 studies
- What was actually found?
Association persists but weakens
- How large was the observed effect?
OR 1.37; 1.19 in better studies
- What do the results mean in everyday life?
Small possible effect
- What are the study's limitations?
Observational
- What does it say about Elawady's specific claim?
Supports an association, not proof of cause
- Do the results apply to Germany and Europe?
Moderate
- What can explicitly not be concluded from this study?
Whether antibiotics cause asthma
Scientific in-depth review
1. Full reference
- Authors
- Zhang Z et al.
- Journal
- World Allergy Organ J
- Year
- 2021
- Identifier
- PMID 34934469 DOI 10.1016/j.waojou.2021.100607
- Verification
- verified – PubMed efetch 2026-10-26 + Crossref
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
Authors report no conflicts (record).
2. Research question
Is infant antibiotic exposure associated with childhood asthma when potential confounders are considered?
3. Study design and population
- Study design
- Meta-analysis – Meta-analysis of observational studies
- Population
Infants and children
- Country
Multinational
- Period
Publications January 2011-March 2021
- Sample size
52 studies
- Inclusion and exclusion criteria
Observational studies
4. Methods and endpoints
- Exposure / intervention
Infant antibiotic exposure
- Comparator
No exposure
- Endpoints
Childhood asthma
- Statistical methods
Random-effects ORs; stratified analyses
5. Actual results
- Results
Overall OR 1.37 (95% CI 1.29-1.45); studies addressing reverse causation and confounding by indication OR 1.19 (1.11-1.28); macrolides OR 1.56; >=5 courses OR 1.79; short time lag OR 2.05 (1.91-2.20).
- Absolute risks
not reported
- Authors' conclusion
Infant antibiotic exposure is associated with increased asthma risk considering confounding; heterogeneity calls for caution.
6. Strengths
- Large number of studies
- Subgroup for reverse causation/confounding by indication
7. Weaknesses
- Observational; heterogeneity
- Short-lag subgroup shows strongest effect, typical of reverse causation
8. Risk of bias
- Orienting tool
- AMSTAR 2
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- some concerns
- Rationale
Overlapping cohorts with earlier meta-analyses.
9. Assessment of the statistical interpretation
Attenuation from 1.37 to 1.19 when bias is addressed (about 45% of the log-excess) and the strongest effect with short time lag both point to partial reverse causation.
10. Relevance to the specific claim
Best pooled estimate of the association.
11. Independent contrary findings
Sibling analyses (I-ABX-03) show further attenuation.
12. Transferability to Germany and Europe
Moderate.
13. Overall methodological judgement
A modest residual association persists, causality unresolved.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | some concerns |
| Precision of results | high |
| Directness | direct |
| Reproducibility | replicated |
| Consistency with the overall evidence | consistent |
| Regional transferability | moderate |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Causal contribution.
15. Linked fact checks
- Antibiotic exposure in early life causes asthma and allergic disease. – Studies supporting the claim