What does this research mean for the field?

Early age at smoking initiation is associated with a 2.43 times higher risk of myocardial infarction and a 1.82 times higher risk of death compared to nonsmokers over nine years. Novelty: ClaimNovelty.NOVEL_FINDING. Consensus alignment: ConsensusAlignment.CHALLENGES_CONSENSUS.

What question did this study set out to answer?

To determine whether early age at smoking initiation independently increases the risks of incident myocardial infarction, stroke, and all-cause mortality.

January 25, 2026

Early age at smoking initiation is associated with elevated cardiovascular disease and mortality risk in a nationwide population-based cohort.

Q: What are the key findings of this study?

Smokers initiating before age 20 with ≥20 pack-years had the highest risks of myocardial infarction (HR 2.43), stroke (HR 1.78), and death (HR 1.82) compared to nonsmokers.

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Key result

Smoking before age 20 with ≥20 pack-years linked to ~143% higher MI risk than nonsmokers.

HR 2.43
HR 1.78
HR 1.82

Why the study?

Smoking causes cardiovascular diseases, but the role of age at smoking initiation in cardiovascular risk has not been fully established.

Does early age at smoking initiation increase the risk of incident MI, stroke, and all-cause mortality in adults without preexisting cardiovascular diseases?

Key Points

To determine whether early age at smoking initiation independently increases the risks of incident myocardial infarction, stroke, and all-cause mortality.
Nationwide population-based cohort study evaluating 9,295,979 Korean adults without preexisting cardiovascular disease screened in 2009, with a nine-year follow-up.
Identified 3,724,368 smokers categorized by initiation age (< 20 versus ≥ 20 years) and cumulative exposure in pack-years (PY).
Calculated hazard ratios for incident myocardial infarction, stroke, composite events, and all-cause mortality using multivariable Cox proportional hazard models.
Among ≥ 20 PY smokers, initiation before age 20 conferred higher risks than nonsmokers for myocardial infarction (adjusted HR 2.43, 95% CI 2.35–2.51) and stroke (adjusted HR 1.78, 95% CI 1.73–1.83) compared to initiation at age ≥ 20 (MI: adjusted HR 1.82, 95% CI 1.78–1.86; stroke: adjusted HR 1.38, 95% CI 1.36–1.41).
For composite MI or stroke and all-cause death, ≥ 20 PY smokers initiating before age 20 had adjusted HRs of 2.00 (95% CI 1.96–2.04) and 1.82 (95% CI 1.79–1.85), respectively, compared to nonsmokers.
Earlier initiation age was significantly associated with increasing pack-year-adjusted risks across all outcomes (p for trend < 0.001 each) and exhibited significant interaction with total pack-years (p < 0.001 each).

Structured PICO

Does early age at smoking initiation increase the risk of incident MI, stroke, and all-cause mortality in adults without preexisting cardiovascular diseases?

Population

9,295,979 Korean adults without preexisting cardiovascular diseases who underwent health screening in 2009

Intervention

Early age at smoking initiation (e.g., < 20 years)

Comparator

Nonsmokers and smokers with initiation age ≥ 20

Outcome

Incident MI, stroke, MI or stroke, and all-cause mortality over a nine-year follow-uphard clinical

Early age at smoking initiation is associated with accentuated, pack-year-dependent increases in the risk of MI, stroke, and mortality.

Implication

Early initiation before age 20 was associated with highest CV risks in heavy smokers; challenges pack-year models and leaves open targeted prevention trials.

Abstract

Smoking is a major cause of cardiovascular diseases, including myocardial infarction (MI) and stroke. However, the role of age at smoking initiation in cardiovascular risk has not been fully established. We selected 9,295,979 Korean adults without preexisting cardiovascular diseases who underwent health screening in 2009. The association of age at initiation with incident MI, stroke, MI or stroke, and all-cause mortality was analyzed using Cox proportional hazard models stratified or adjusted for total pack-years (PY). Among the 3,724,368 smokers, 876,740 smokers (23.5%) started before age 20, and 75,299 smokers (2.0%) had age at initiation < 15. Over a nine-year follow-up, ≥ 20 PY smokers with age at initiation < 20 had the highest risks of MI (adjusted hazard ratio (HR), 2.43; 95% confidence interval (95% CI), 2.35-2.51), stroke (HR 1.78, 95% CI 1.73-1.83), MI or stroke (HR 2.00, 95% CI 1.96-2.04), and death (HR 1.82, 95% CI 1.79-1.85) relative to nonsmokers, significantly higher than in ≥ 20 PY smokers with initiation age ≥ 20. Earlier age at initiation was associated with increasing PY-adjusted risks of each outcome (p for trend < 0.001 each). Age at initiation also had significant interactions with total PY for each outcome (p < 0.001 each), with PY-dependent risk increases accentuated by earlier initiation. Early age at smoking initiation is associated with increased risks of MI and stroke. Focused smoking prevention measures may be warranted for both adolescents and young adults.

Discussion

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Published by the journal · CC BY-NC-ND

Cite This Study

Koh et al. (2026) studied this question. Smokers initiating before age 20 with ≥20 pack-years had the highest risks of myocardial infarction (HR 2.43), stroke (HR 1.78), and death (HR 1.82) compared to nonsmokers.

synapsesocial.com/papers/6975b2eafeba4585c2d6e707 https://doi.org/10.1038/s41598-025-88253-4

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Implication

Early initiation before age 20 was associated with highest CV risks in heavy smokers; challenges pack-year models and leaves open targeted prevention trials.

Early age at smoking initiation is associated with elevated cardiovascular disease and mortality risk in a nationwide population-based cohort.

Key Points

Structured PICO

Implication

Abstract

Discussion

Figures from the paper

Cite This Study

Early age at smoking initiation is associated with elevated cardiovascular disease and mortality risk in a nationwide population-based cohort.

Key Points

Structured PICO

Implication

Abstract

Discussion

Figures from the paper

Cite This Study

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