Smoking causes one in 10 deaths worldwide, new study shows, half of them in just four countries – China, India, the US and Russia.
Despite decades of tobacco control policies, population growth has seen an increased number of smokers, it warned.
Researchers said mortality could rise further as tobacco companies aggressively targeted new markets, especially in the developing world.
The report was published in the medical journal The Lancet.
“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 Global Burden of Diseases report was based on smoking habits in 195 countries and territories between 1990 and 2015.
It found that nearly one billion people smoked daily in 2015 – one in four men and one in 20 women.
That was a reduction from one in three men and one in 12 women who lit up in 1990.
However, population growth meant there was an increase in the overall number of smokers, up from 870 million in 1990.
And the number of tobacco-related deaths – more than 6.4 million in 2015 – increased by 4.7% over the same period.
The study found some countries had succeeded in efforts to help people quit, mostly through a combination of higher taxes, warnings on packages and education programmes.
Over the 25-year period, Brazil had seen the percentage of daily smokers drop from 29% to 12% among men and from 19% to 8% among women.
But, the report said, Bangladesh, Indonesia and the Philippines saw no change from 1990 to 2015.
Russia saw smoking among women rise by 4% over the same period and similar trends were emerging in parts of Africa, the authors warned.