Cohort studyindependent cross-checkabstract checked★ key study I-INS-105 in-depth review
Blood sugar control in childhood type 1 diabetes and adult height
Glycemic Control and Adult Height: A Nationwide Swedish Cohort Study on Childhood Type 1 Diabetes.
Overview
Smew AI et al.. J Clin Endocrinol Metab 2025 · PMID 39556501 · DOI 10.1210/clinem/dgae809
Children with poorly controlled type 1 diabetes ended up about 2-3 cm shorter as adults than those with good control.
Does the study support the specific claim? No · Methodological quality: moderate
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Relate childhood glucose control to adult height.
- How was the study done?
Nationwide register study.
- How many people, animals or samples were studied?
Swedish children with T1D.
- What was actually found?
Poor control = lower adult height.
- How large was the observed effect?
-2.9 cm (males), -1.8 cm (females).
- What do the results mean in everyday life?
Keeping blood sugar well controlled with insulin protects growth.
- What are the study's limitations?
Observational.
- What does it say about Elawady's specific claim?
Contradicts the idea that insulin itself causes short stature.
- Do the results apply to Germany and Europe?
Swedish data; applicable to Europe.
- What can explicitly not be concluded from this study?
Cannot exclude other factors linked to poor control.
Scientific in-depth review
1. Full reference
- Authors
- Smew AI et al.
- Journal
- J Clin Endocrinol Metab
- Year
- 2025
- Identifier
- PMID 39556501 DOI 10.1210/clinem/dgae809
- 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; Karolinska Institutet (record).
2. Research question
Is glycaemic control in childhood T1D associated with final adult height and short stature?
3. Study design and population
- Study design
- Cohort study – Nationwide population-based cohort (Swedish National Diabetes Register)
- Population
All individuals with childhood-onset T1D in the register
- Country
Sweden
- Period
Register data (years as in paper)
- Sample size
Nationwide childhood-onset T1D cohort (n not stated in abstract)
- Inclusion and exclusion criteria
Childhood-onset T1D with height and HbA1c data
4. Methods and endpoints
- Exposure / intervention
Suboptimal (HbA1c 53-75 mmol/mol) or poor (>75 mmol/mol) control
- Comparator
Optimal control (<53 mmol/mol)
- Endpoints
Final adult height; short stature
- Statistical methods
Linear and logistic regression
5. Actual results
- Results
Poor control associated with lower adult height: -2.91 cm (95% CI -3.48 to -2.33) in males, -1.83 cm (-2.42 to -1.23) in females; short stature OR 1.90 (1.07-3.35) in males, 0.73 (0.36-1.51) in females. In females the effect was confined to prepubertal onset and prepubertal poor control.
- Absolute risks
not reported
- Authors' conclusion
Poor glycaemic control after onset of T1D is associated with lower adult height; the prepubertal period seems more critical for females.
6. Strengths
- Nationwide
- Final height outcome
7. Weaknesses
- Observational
- Sample size not given in abstract
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 adherence/social factors possible.
9. Assessment of the statistical interpretation
Effect is a few centimetres and linked to poor control (i.e. insufficient insulin effect), not to insulin use as such.
10. Relevance to the specific claim
Growth impairment in childhood T1D is linked to poor glycaemic control, which reflects insufficient insulin action; this contradicts 'insulin before puberty causes short stature'.
11. Independent contrary findings
12. Transferability to Germany and Europe
Directly applicable; same biology and clinical standards in Europe.
13. Overall methodological judgement
Good-quality evidence that the growth problem comes from poorly controlled diabetes.
| 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 | consistent |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |