Tobacco use fell by 2.5 percent worldwide a decade after the first global health treaty went into effect, World Health Organization researchers said Wednesday.
Smoking rates declined most sharply when countries implemented several of the measures called for in the 2005 pact, and rose in some nations that failed to do so, suggesting anti-tobacco policies make a real difference, they reported in The Lancet, a medical journal.
The WHO Framework Convention on Tobacco Control's 180 signatories agreed to introduce or boost tobacco taxes, smoke-free zones, warning labels, advertising bans, and programmes to help people kick the nicotine habit.
The study, based on data from 126 nations, showed that the treaty "has been a success in reducing tobacco use in countries that engaged in strong implementation," said co-author Geoffrey Fong, a professor at the University of Waterloo.
Tobacco consumption is the single greatest preventable cause of death in the world, claiming nearly six million lives annually.
Smoking also racks up more than a trillion dollars annually in health care and lost productivity costs.
On average, smoking rates across the 126 nations dropped from 24.7 to 22.2 percent over the decade examined.
But trends varied widely across regions: smoking decreased in 90 countries, stayed the same in 12, and increased in 24.
In northern Europe and South America -- where governments put in place many of the anti-tobacco measures -- smoking rates fell by 7.1 and 6.8 percent, respectively, between 2005 to 2015.
Africa, meanwhile, saw increases over the same period: 3.4 percent in western Africa, 12.6 percent in central Africa, and 4.6 percent in the northern part of the continent.
Application of the treaty measures was lax to non-existent in most of these regions.
The findings "give tobacco activists an empirical argument with which to prod their governments into living up to their treaty obligations," said Kenneth Warner, a professor at the University of Michigan's School of Public Health.
Early research leaves little doubt that higher taxation is most effective in discouraging smokers, especially in low- and middle-income countries.
Graphic warnings on packages is thought to be among the least persuasive policies.
The most frequently implemented measure was smoke-free public places, adopted by 28 percent of the 126 nations.
The least frequently adopted policy -- present in only 13 percent of countries -- was a ban on advertising, which is thought to reduce the number of people who start smoking in the first place.
Nations adopting aggressive campaigns against tobacco included Panama and Nepal, both of which opted for a complete smoke-free policy coupled and broad bans on advertising and sponsorship.
More recently, Nepal also introduced the world's largest warnings, which take up 90 percent of the front and back of each pack of cigarettes.