Starting to Smoke: Why Age Matters More Than Quantity

A large national study shows that starting to smoke before the age of 20 leaves a lasting cardiovascular footprint, intensifying damage from smoking and increasing the risk of heart attack, stroke, and premature death into adulthood.

Study: Early age at smoking initiation is associated with elevated risk of cardiovascular disease and mortality in a population-based national cohort. Image Credit: Gudman/Shutterstock

In a recent study published in the journal Scientific Reports, researchers investigated whether the age at which people start smoking was independently associated with future risks of myocardial infarction (MI), combined cardiovascular events, all-cause mortality, and stroke.

Individuals who started smoking younger, particularly before age 20, had significantly higher risks of death, stroke, and MI compared to later-onset smokers, even at the same level of cumulative smoking exposure. This suggests an additional risk beyond the total smoking dose, measured in pack-years, while acknowledging that age of initiation and lifetime exposure remain closely related behaviors.

Smoking as a major cardiovascular risk factor

Smoking is a leading cause of preventable death worldwide and remains a major contributor to cardiovascular disease, including MI and stroke. Abundant evidence demonstrates that greater cumulative smoking exposure,measured in pack-years,increases cardiovascular risk.

However, this dose-response relationship is not entirely linear, as even light smoking can substantially increase risk, suggesting that the use of pack-years as an indicator may not fully account for smoking-related harm.

Importance of age at smoking initiation

Early Smoking Increases heart Disease, Death Risk

Starting to smoke at a younger age significantly increases the risk of heart attack and stroke, even when accounting for how much a person smokes over their lifetime, a new study finds. Researchers observed these heightened risks after following a large group of smokers for nearly nine years.

Smoking Habits in the Studied Population

According to the study, 40.1% of participants had a history of smoking, and nearly a quarter of those smokers had started before the age of 20. Over approximately nine years of follow-up, all groups of smokers showed a higher likelihood of cardiovascular events and mortality compared to non-smokers. The highest risks were seen in individuals who began smoking early and accumulated high exposure – 20 pack-years or more.

Cardiovascular Risk and Mortality by Age of Initiation

Compared to non-smokers, people who started smoking early and had high exposure faced more than double the risk of myocardial infarction (MI) – a heart attack (Hazard Ratio [HR] 2.43) – a significantly increased risk of stroke (HR 1.78), combined coronary heart disease or MI (HR 2.00), and elevated all-cause mortality (HR 1.82). These risks were significantly higher than those observed in smokers with a similar number of pack-years who started smoking later in life.

Interaction Between Early initiation and Smoking Intensity

The study demonstrated a clear dose-response relationship: earlier initiation was linked to a progressively higher risk of cardiovascular disease, even after adjusting for total pack-years. Notable interactions indicated that the harmful effects of greater tobacco exposure were amplified when smoking began at a younger age. These trends remained consistent across subgroups defined by sex, metabolic health, smoking status, and different exposure thresholds.

Associations with all-cause mortality were similar but generally weaker than those observed for cardiovascular outcomes,particularly among younger participants. The authors suggest this may reflect a limited follow-up duration for mortality parameters.

Study Interpretation, Strengths, and Limitations

This national study demonstrates that beginning to smoke at a younger age substantially increases the risk of MI and stroke after statistical adjustment for cumulative smoking exposure, and that early initiation intensifies the cardiovascular damage associated with heavier smoking. These findings suggest increased vulnerability during adolescence and early adulthood, while remaining consistent with an observational, non-causal interpretation.

Key strengths include the exceptionally large sample size, long follow-up, and detailed adjustment for clinical, behavioral, and socioeconomic confounding factors, allowing for a robust assessment of the interactions between age of smoking initiation and smoking intensity.

Though, limitations include reliance on self-reported smoking data, potential recall bias, a lack of information on changes in smoking habits over time or duration of cessation, and unmeasured confounding factors such as diet, family history, and genetic risk. The cohort was predominantly male and Asian, which may limit generalizability.

Public Health Implications

These results indicate that preventing young people from starting to smoke, particularly before the age of 20, could have substantial effects on reducing cardiovascular disease and premature deaths at the population level.