Starting to smoke in childhood is much more dangerous than starting later

21 May 2020

  • Starting to smoke in childhood doubles the risk of premature death
  • The greatest risk is for those who start smoking before age 15, or even before age 10
  • Quitting smoking before 40 (preferably well before 40) avoids more than 90% of the risk

Smoking causes about 100,000 deaths a week worldwide, which is even more than COVID is now causing. Most smokers start before age 20, and in countries such as Cuba or the US where tobacco is grown many start in childhood (before age 15) and some even start before 10. Prospective studies in Cuban and US adults now show that starting smoking in childhood is particularly dangerous.

Starting to smoke in childhood doubles the risk of premature death, according to a new study published today in The Lancet Global Health. The greatest risk is for those who start smoking before the age of 10. However, stopping before age 40 substantially reduces the excess risk of death. 

UK and US researchers from the Nuffield Department of Population Health (NDPH) at Oxford University, together with Cuban researchers from the National Institute of Cardiology in Havana, led a prospective study of smoking and mortality that included 120,000 men and women age 30-70 in five Cuban provinces. Participants were asked whether they smoked and how old they had been when they started smoking. They were then followed for an average of 17 years to compare their risks of premature death (before age 70).

This Cuban study found that those who had started to smoke before age 15 had twice the risk of premature death of those who had never smoked, with even greater risks among those who had started to smoke before age 10. Although it was expected that smoking from such young ages would carry considerable health risks, the magnitude of these risks were not known.

One-third of the current smokers had begun smoking regularly before age 15, and 4% had begun smoking regularly before age 10. Among those who began smoking before age 15, approximately half would eventually be killed by their habit. However, quitting smoking before about age 40 (preferably well before 40) avoids more than 90% of the excess risk of death, as in the UK and other populations.

To validate these findings, the researchers also examined the association between childhood smoking uptake and adult mortality in a prospective study of 300,000 adults in the United States, yielding similar results. They conclude that the 5 million daily smokers in the United States who began smoking before age 15, of whom 0.5 million began before age 10, are at particularly high risk of premature death if they do not quit.

Senior author Sarah Lewington, Professor of Epidemiology at the Nuffield Department of Population Health, University of Oxford, said, ‘Starting to smoke before 15 is common in many populations. Millions who began smoking in childhood will die prematurely from tobacco, unless they stop.’

Dr Blake Thomson, a US academic visitor who conducted the analyses, added, ‘Even among smokers who started in childhood, the sooner they quit the lower their risk of premature death. Smokers who quit before age 40 (preferably well before 40) avoid more than 90% of the risk.’

Co-author Sir Richard Peto said, ‘Worldwide, about 100 million smokers started before the age of 15 and more than half will be killed by tobacco unless they stop. Alfredo Duenas (1940-2020), Director of the National Cardiology Institute in Havana, got this large prospective study going more than 20 years ago despite the limited resources in Cuba and helped lead it for the rest of his life, hoping its findings would help people everywhere to avoid premature death and disability from continuing to smoke.’

For a copy of the paper or interviews, please contact:

Notes to editors:

The paper will be available at the following link post-embargo:

Funding: UK Medical Research Council, Cancer Research UK, British Heart Foundation, and US CDC Foundation.

About the University of Oxford
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About the Nuffield Department of Population Health (NDPH)
The Nuffield Department of Population Health (NDPH) is a world-leading research institute, based at the University of Oxford that investigates the causes and prevention of disease. NDPH has over 750 staff, students and academic visitors working in a number of world-renowned population health research groups, including the Clinical Trial Service Unit and Epidemiological Studies Unit (CTSU), and the MRC Population Health Research Unit (MRC PHRU), and other groups working on cancer epidemiology, perinatal epidemiology, public health, health economics, ethics and health record linkage. It is also a key partner in the Oxford University Big Data Institute. For further information, please visit

About the Cuban National Institute of Cardiology and Cardiovascular Surgery
Founded in 1966, this Institute is a referral centre dedicated to research, assistance of doctors throughout Cuba, and postgraduate training of specialists. Generations of cardiologists and cardiovascular surgeons have been trained and graduated at the Institute. It promotes scientific research and technological innovation in the field of cardiology and cardiovascular surgery to address the health problems of the population, and trains the scientific and professional personnel who will provide tertiary care and advise the wider national health system.