More than one in 10 deaths worldwide (equivalent to 6.4 million deaths per year) are caused by smoking, new figures suggest.
Half of these deaths occur in just four countries: China, India, USA, and Russia.
The new estimates are based on smoking habits in 195 countries and territories between 1990 and 2015, and illustrate that smoking remains a leading risk factor for death and disability.
With growing and ageing populations already heightening the burden of tobacco, it will be crucial to support more smokers to quit and stop people from starting smoking, the researchers said.
Despite many countries (including the UK) enforcing restrictions around smoking such as the ban on lighting up inside, the authors of the study warn that the “war against tobacco” is far from won, and argue that policy makers need renewed and sustained efforts to tackle the epidemic.
Worldwide, between 1990 and 2015, smoking prevalence decreased by almost a third (29.4%) to 15.3% in 2015, and today, one in four men (25%) worldwide smoke, as do one in 20 women (5.4%).
Despite these improvements, population growth has led to an increase in the overall number of smokers, increasing from 870.4 million in 1990 to 933.1 million in 2015.
Deaths attributable to smoking increased by 4.7% in 2015 compared with 2005 and smoking was rated as a bigger burden on health - moving from third to second highest cause of disability.
“Despite more than half a century of unequivocal evidence of the harmful effects of tobacco on health, today, one in every four men in the world is a daily smoker,” said senior author Dr Emmanuela Gakidou.
“Smoking remains the second largest risk factor for early death and disability, and so to further reduce its impact we must intensify tobacco control to further reduce smoking prevalence and attributable burden.”
The 10 countries with the largest number of smokers in 2015 were China, India, Indonesia, USA, Russia, Bangladesh, Japan, Brazil, Germany and the Philippines - who together accounted for almost two-thirds of the worlds smokers (63.6%).
The researchers said high smoking prevalence levels and worrying trends persist. For instance, Indonesia, Bangladesh and the Philippines saw no significant reductions in male smoking prevalence between 1990 and 2015 (2015 smoking rates were 46.7%, 38.0% and 34.5%, respectively), and in Russia, female smoking prevalence has increased (from 7.9% in 1990 to 12.3% in 2015) and comprehensive tobacco control policies were only implemented in 2014.
The authors noted that Indonesia has very high smoking levels.
In contrast, Brazil, which has been a leader in tobacco control, showing one of the largest reductions in smoking prevalence for men and women between 1990 and 2015 - halving from 28.9% to 12.6% in men and 18.6% to 8.2% in women.
“There have been some success stories, but smoking remains the leading cause of death and disability in 100 countries in 2015,” said Dr Gakidou.
“Its toll will remain substantial without more concerted policy initiatives, policy compliance and enforcement, and sustained political will to offset commercial interests.
“Despite progress in some settings, the war against tobacco is far from won, especially in countries with the highest numbers of smokers. The staggering toll of smoking on health echoes well beyond the individual, especially as tobacco threatens to exact long-term financial and operational burdens on already resource-constrained health systems.
“To markedly bend the global tobacco epidemic’s trajectory, a renewed and sustained focus is needed on comprehensive tobacco control policies around the world. Success is possible, but requires effective and aggressively enforced policies and laws.”
The study estimates were based on the number of people who smoked every day, rather than occasional or former smokers, and did not take into account how many cigarettes a person smoked in a day nor people who used smokeless tobacco products or e-cigarettes.
Writing in a linked comment, Professor John Britton, University of Nottingham, UK, said: “Today, the smoking epidemic is being exported from the rich world to low-income and middle-income countries, slipping under the radar while apparently more immediate priorities occupy and absorb scarce available human and financial resources.
“The epidemic of tobacco deaths will progress inexorably throughout the world until and unless tobacco control is recognised as an immediate priority for development, investment, and research.”
The report is published in the Lancet journal.