Smoking is one of the most preventable causes of disease and death globally, contributing substantially to cardiovascular conditions such as heart attacks and strokes. While public health campaigns have long emphasised how much a person smokes, a groundbreaking cohort study published in Scientific Reports suggests that when someone starts smoking matters just as much, if not more, for long-term health outcomes. The research, which drew on health data from more than 9 million adults in Korea, found that individuals who began smoking before the age of 20 had markedly higher risks of stroke, heart attack and all-cause mortality compared with those who started later in life, even when they had smoked the same number of cigarettes over time.
This important distinction challenges traditional measures of smoking harm, which rely heavily on cumulative exposure (like pack-years), and instead highlights age at initiation as a key factor influencing cardiovascular risk. With stroke already a leading cause of disability and death globally, especially among young adults, understanding how early smoking affects lifelong risk has profound implications for tobacco control efforts, public health policy and preventive medicine.
Why Age of Smoking Initiation Matters
Historically, smoking risk has been calculated using pack-years, the product of average cigarettes smoked per day and years smoked. While this remains important, the new study shows that starting younger confers additional risk for cardiovascular events including stroke and death, beyond what pack-years alone would predict.
Researchers found that among people with similar cumulative exposure, those who began smoking before age 20 had substantially higher risks of stroke (hazard ratio around 1.78) and myocardial infarction (heart attack) compared with later starters, reinforcing age of initiation as an independent risk factor.
Early tobacco use may intensify biological vulnerability during key developmental periods and foster stronger nicotine dependence, making quitting harder and leading to longer lifetime exposure, even if total pack-years appear similar.
Also Read: Why "Just Quit Smoking" Doesn't Work: Ex-Smokers Share The Real Struggles
Stroke and Smoking: Established Risks
Decades of research confirm that smoking itself dramatically raises the likelihood of stroke, irrespective of age at initiation. The long-running Framingham Heart Study showed that smokers had a significantly higher risk of stroke than non-smokers, and that risk increased with the number of cigarettes smoked.
Other large population studies echo these findings, revealing that smokers are substantially more likely than non-smokers to experience stroke across age groups, with particularly high risk among younger adults and women.
Biologically, tobacco smoke damages blood vessels, accelerates atherosclerosis, increases blood clot formation, and elevates blood pressure. All of these are pathways that directly contribute to stroke and other cardiovascular events.
Key Findings from the Nationwide Korean Cohort
The Scientific Reports study leveraged health records from a mandatory national screening programme, tracking individuals over approximately nine years. The analysis focused on stroke, heart attack, combined cardiovascular events and mortality.
- Higher Stroke Risk: Individuals who started smoking before age 20 and accumulated high exposure had significantly elevated stroke risk (around 78% higher) compared to non-smokers.
- Increased Heart Attack and Combined Risk: Early starters also faced much higher risks of myocardial infarction and combined stroke/MI outcomes.
- Greater All-Cause Death Risk: Early initiation correlated with a notable increase in overall mortality.
- Dose-Response Interaction: Younger initiation amplified the harmful effects of heavier smoking, reinforcing a dose-response relationship.
These patterns held true across demographic and health subgroups, including sex and metabolic health profiles.
Why Early Smoking Causes Greater Harm
Several biological and behavioural mechanisms may explain why younger smoking initiation increases stroke risk beyond cumulative exposure:
- Developing Bodies Are More Vulnerable: Adolescence and early adulthood involve ongoing growth of cardiovascular and brain tissue, potentially making them more susceptible to tobacco's damaging effects.
- Stronger Nicotine Dependence: Starting young is associated with more entrenched smoking habits and difficulty quitting, often leading to longer lifetime duration of tobacco use.
- Metabolic and Inflammatory Effects: Early tobacco exposure may trigger long-lasting inflammatory and vascular changes that predispose individuals to stroke later in life, even beyond measured exposure.
Public Health Implications
The study's findings have significant implications for tobacco control and stroke prevention:
- Prevention Efforts Must Target Youth: Delaying or preventing the initiation of smoking during adolescence could dramatically reduce long-term cardiovascular risk on a population level.
- Educational Campaigns: Highlighting the unique risks associated with early smoking may strengthen public health messaging, especially in schools and communities.
- Policy Actions: Taxes, advertising bans and age restrictions have proven effective in reducing youth smoking rates. Sustained policy efforts could amplify these benefits.
The age at which a person begins smoking plays a critical role in determining their long-term risk of stroke and other cardiovascular diseases. Starting before age 20 significantly amplifies these risks, even among individuals with similar lifetime smoking exposure, highlighting the importance of early preventive interventions. With cardiovascular diseases already major causes of global mortality, these findings reinforce the urgent need to protect young people from tobacco initiation and to support cessation at any age.
Disclaimer: This content including advice provides generic information only. It is in no way a substitute for a qualified medical opinion. Always consult a specialist or your own doctor for more information. NDTV does not claim responsibility for this information.
