Cohort studyindependent cross-checkabstract checked★ key study I-SRC-113 in-depth review
Smoking costs more than ten years of life
21st-century hazards of smoking and benefits of cessation in the United States.
Overview
Jha P et al.. N Engl J Med 2013 · PMID 23343063 · DOI 10.1056/NEJMsa1211128
In over 200,000 US adults, smokers died at about three times the rate of never-smokers; quitting before 40 removed about 90% of the excess risk.
Does the study support the specific claim? No · Methodological quality: high
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Measure smoking harms and quitting benefits
- How was the study done?
National cohort
- How many people, animals or samples were studied?
202,248 adults
- What was actually found?
Threefold mortality; >10 years life lost
- How large was the observed effect?
HR 3.0 women, 2.8 men
- What do the results mean in everyday life?
Smoking is deadly; quitting helps
- What are the study's limitations?
Self-report
- What does it say about Elawady's specific claim?
Contradicts the claim
- Do the results apply to Germany and Europe?
High
Scientific in-depth review
1. Full reference
- Authors
- Jha P et al.
- Journal
- N Engl J Med
- Year
- 2013
- Identifier
- PMID 23343063 DOI 10.1056/NEJMsa1211128
- Verification
- verified – PubMed efetch 2026-10-26; Crossref works record checked
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
NIH, CIHR and UK MRC funding.
2. Research question
What are the current mortality hazards of smoking and the benefits of quitting in the US?
3. Study design and population
- Study design
- Cohort study – Prospective cohort (US National Health Interview Survey linked to death records)
- Population
US adults aged 25+ interviewed 1997-2004
- Country
USA
- Period
Deaths to 31 December 2006
- Sample size
113,752 women and 88,496 men; 15,715 deaths
- Inclusion and exclusion criteria
Nationally representative survey participants
4. Methods and endpoints
- Exposure / intervention
Current smoking; quitting age
- Comparator
Never smokers
- Endpoints
All-cause and cause-specific mortality
- Statistical methods
Cox HR (99% CI), adjusted for age, education, adiposity, alcohol
5. Actual results
- Results
All-cause mortality HR current vs never smokers: women 3.0 (99% CI 2.7-3.3), men 2.8 (2.4-3.1). Probability of surviving from 25 to 79: 70% vs 38% (women), 61% vs 26% (men). Life expectancy shortened by more than 10 years. Quitting at 25-34, 35-44 or 45-54 gained about 10, 9 and 6 years.
- Absolute risks
Survival to 79: 70% vs 38% (women); 61% vs 26% (men).
- Authors' conclusion
Smokers lose at least a decade of life expectancy; cessation before age 40 reduces the excess risk of death by about 90%.
6. Strengths
- Nationally representative
- Large
7. Weaknesses
- Self-reported smoking
- Observational
8. Risk of bias
- Orienting tool
- ROBINS-E
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- low
- Rationale
Effect size far larger than plausible confounding.
9. Assessment of the statistical interpretation
Large effect (HR about 3) with tight CIs; absolute survival differences 32-35 points (stats/C-SRC-62_smoking.py).
10. Relevance to the specific claim
Directly contradicts 'cigarettes are beneficial or not harmful'.
11. Independent contrary findings
I-SRC-126 (inverse associations with a few diseases do not offset harms).
12. Transferability to Germany and Europe
Applicable.
13. Overall methodological judgement
High-quality evidence of large harm.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | high |
| Risk of bias | low |
| Precision of results | high |
| Directness | direct |
| Reproducibility | replicated |
| Consistency with the overall evidence | consistent |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |