Cohort studycited by the Tayebat archivefull text checked A-ABX-02 in-depth review

Infant antibiotics and body mass (UK)

Infant antibiotic exposures and early-life body mass.

Overview

Trasande L et al.. Int J Obes (Lond) 2013 · PMID 22907693 · DOI 10.1038/ijo.2012.132

Antibiotics before 6 months were linked to slightly higher body mass later.

Does the study support the specific claim? Partly · Methodological quality: moderate

Original publication

Plain-language summary

Study explained simply

What did the researchers want to find out?: Link antibiotics to weight.
How was the study done?: Birth cohort.
How many people, animals or samples were studied?: 11,532.
What was actually found?: Antibiotics before 6 months: body mass slightly higher at 10-38 months (+0.07 to +0.1 SD), overweight odds 1.22 at 38 months; no clear effect at 7 years; later exposures not consistently linked.
How large was the observed effect?: +0.067 SD BMI at 38 months, about 90 g; overweight OR 1.22.
What do the results mean in everyday life?: Small.
What are the study's limitations?: Parent-reported antibiotics; infections themselves not accounted for; effect not seen at 7 years; many comparisons.
What does it say about Elawady's specific claim?: Supports association.
Do the results apply to Germany and Europe?: High.
What can explicitly not be concluded from this study?: Causation, or a lasting effect on obesity beyond early childhood.

Scientific in-depth review

1. Full reference

Authors: Trasande L, Blustein J, Liu M, Corwin E, Cox LM, Blaser MJ
Journal: Int J Obes (Lond)
Year: 2013
Identifier: PMID 22907693 DOI 10.1038/ijo.2012.132 · PMC3798029
Verification: verified – PubMed E-utilities efetch, 2026-10-25
Retracted: no
Corrections: none
Extent checked: full text
Conflicts of interest and funding: Authors declare no conflict of interest. ALSPAC core support: UK Medical Research Council, Wellcome Trust (092731), University of Bristol; analysis: NYU Global Public Health Research Challenge Fund pilot grant, NIH grants RO1GM090989 and 1UL1RR029893.

2. Research question

Antibiotic exposure in first 2 years and body mass to 7 years

3. Study design and population

Study design: Cohort study – Prospective population-based birth cohort (ALSPAC) analysed with multivariable mixed-effect (random-effects) linear and logistic models; STROBE-conform
Population: Children born >=2500 g in Avon, UK, 1991-1992 (92.6% white; slightly more affluent than UK population; 85% of eligible births captured)
Country: UK
Period: Births April 1991-December 1992; follow-up to age 7 years
Sample size: 11,532 analysed (from 14,541 pregnancies; 13,988 alive at 1 year); outcome n varies (e.g. 9,443 at 38 months, 8,210 at 7 years)
Inclusion and exclusion criteria: Included: birth weight >=2500 g, alive at 1 year, antibiotic information for at least one window; excluded Z-score outliers >=5 or <=-5

4. Methods and endpoints

Exposure / intervention: Parent-reported antibiotic exposure (yes/no) in three windows: <6 months (31.9%), 6-14 months (53.6%), 15-23 months (47.5%); type and dose not usable
Comparator: Children not exposed in the same window; negative-control exposures (antipyretics, eye ointment)
Endpoints: WHO weight-for-length Z-score (6 weeks, 10 and 20 months), UK-1990 BMI Z-score (38 months, 7 years), overweight (85th-94th percentile) and obesity (>=95th percentile) at 38 months and 7 years
Statistical methods: Mixed models with subject random effects, separate per window; adjusted for birth weight, parity, race, social class, education, parental BMI, first-trimester smoking, breastfeeding, complementary-food timing, TV/car time, dietary pattern at 38 months, sleep at 7 years; missing-indicator category for covariates; CIs shown only graphically

5. Actual results

Results: Exposure <6 months: weight-for-length Z +0.106 SD at 10 months (P<0.001) and +0.083 at 20 months (P<0.001 in results text; abstract P=0.001); BMI Z +0.067 at 38 months (P=0.009); overweight at 38 months OR 1.22 (P=0.029); obesity at 38 months OR 1.23 (P=0.097); no significant association at 7 years. Exposure 6-14 months: no association. Exposure 15-23 months: only BMI Z +0.049 at 7 years (P=0.050). Normal-weight mothers: <6-month exposure associated with 29.4% increase in overweight at 38 months (P=0.032); overweight/obese mothers OR 1.07 (P=0.752). Antipyretics and eye ointment: no association. 95% CIs reported only in figures, not numerically.
Absolute risks: Authors' translation: +0.067 SD BMI Z-score at 38 months = about +90 g body weight; assuming normal distribution, population overweight +1.62% and obesity +0.72% (modelled, not observed)
Authors' conclusion: Antibiotic exposure in the first 6 months is associated with consistent modest increases in body mass from 10 to 38 months; later exposures are not consistently associated; effects modest individually but potentially relevant for population health; further studies needed to isolate effects.

6. Strengths

Large population-based prospective cohort with repeated body-mass measures
Extensive confounder adjustment
Negative-control medications (antipyretics, eye ointment)
Examination of timing windows and temporal patterns

7. Weaknesses

Parental recall of antibiotic use over 3-9 months; no type, dose or route
Confounding by indication (infections) not addressed; residual confounding acknowledged by authors
Missing-indicator method for covariates can bias estimates
Many outcomes x windows x time points without multiplicity adjustment; P=0.050 and P=0.029 borderline
Association did not persist to 7 years
Body mass from health-visitor records for most children before 7 years
Early-1990s, largely white cohort

8. Risk of bias

Orienting tool: ROBINS-E
Type of assessment: structured assessment based on the full text by a single reviewer (no formal double review)
Full formal assessment: no
Overall risk of bias: some concerns
Rationale: Single-reviewer structured ROBINS-E-oriented judgement based on the full text; not formal (needs two independent reviewers and a protocol).

8. Risk of bias
Domain	Judgement	Rationale
Confounding	some concerns	Rich adjustment and negative-control exposures, but infections/illness (indication) and family susceptibility not controlled; no sibling design.
Measurement of exposure	some concerns	Parental questionnaire recall, binary, no dose/type; likely non-differential but imprecise.
Selection of participants	low	Population-based cohort; exclusion of <2500 g births is pre-specified and outcome-independent.
Post-exposure interventions	not applicable	Not relevant for this exposure-outcome question.
Missing data	some concerns	Outcome n falls to 8,210 at 7 years; missing-indicator approach for covariates.
Measurement of outcome	low	Objective anthropometry (health visitor records/clinic), unlikely to depend on exposure.
Selection of reported result	some concerns	Multiple windows, time points and outcomes; maternal-weight stratification shown as 'data not shown'; borderline P values.

Full-text review (25 October 2026): Added no association at 7 years, 15-23-month BMI effect at 7 years (P=0.050), obesity OR 1.23 (P=0.097), maternal-weight interaction, absolute translation (+90 g; +1.62% overweight), funding/COI, missing-indicator method and confounding by indication; noted abstract/results discrepancy (0.105 vs 0.106; P=0.001 vs <0.001); full ROBINS-E domains (overall unchanged).

9. Assessment of the statistical interpretation

Effects are small (0.07-0.1 SD; about 90 g at 38 months) and transient (not significant at 7 years); several P values are borderline (0.029, 0.050) amid many comparisons. Population-level overweight increase of 1.62% is a model-based extrapolation.

10. Relevance to the specific claim

C-ABX-05.

11. Independent contrary findings

12. Transferability to Germany and Europe

High (UK).

13. Overall methodological judgement

Modest, transient association between antibiotics before 6 months and body mass in a UK cohort, with negative controls but no control for the infections being treated. Consistent with, but does not prove, a causal effect; does not show that antibiotic courses cause obesity later in childhood.

Multidimensional assessment
Multidimensional assessment
Authenticity of the source	verified
Methodological quality	moderate
Risk of bias	some concerns
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

Sibling or indication-controlled designs; dose/type effects; persistence beyond early childhood.

15. Linked fact checks

Antibiotics make people (especially children) gain weight by altering gut bacteria, as they do in fattened poultry; early-childhood antibiotic courses raise obesity risk. – Studies with mixed or unclear results

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: Bibliography only.
A. What was actually studied?: Antibiotics and body mass.
B. What did the authors find?: Exposure <6 months associated with +0.07 to +0.1 SD body mass at 10-38 months and overweight OR 1.22 at 38 months; no association at 7 years; later windows not consistently associated.
C. What conclusions do the authors themselves draw?: Modest at individual level.
D. What does the archive derive from it?: Supports obesity link.
E. Is this derivation scientifically justified?: Partly: justified as a modest early-childhood association; not as proof that antibiotics cause lasting obesity (effect gone by 7 years, confounding by indication possible).
Adequacy of the interpretation (by the archive): not applicable