(CNN) -- About half the men in numerous developing nations use tobacco, and women in those regions are taking up smoking at an earlier age than they used to, according to what is being called the largest-ever international study on tobacco use.
The study, which covered enough representative samples to estimate tobacco use among 3 billion people, "demonstrates an urgent need for policy change in low- and middle-income countries," said lead researcher Gary Giovino, whose report was published in the British medical journal The Lancet.
The figures bolster statements by the World Health Organization that while much of the industrialized world, including the United States, has seen a substantial reduction in smoking in recent years, the opposite trend is under way in parts of the developing world.
The WHO warns that "if current trends continue, it will cause up to one billion deaths in the 21st century."
The new study, the Global Adult Tobacco Survey (GATS), focused on countries in which smoking is known to be a growing problem.
"The burden of tobacco use is moving," says Giovino, who formerly oversaw the Office on Smoking and Health at the Centers for Disease Control and Prevention.
"The tobacco epidemic takes different forms in different countries," he said in an interview with CNN, pointing out that chewing tobacco and other smokeless forms are part of the problem. "But manufactured cigarettes are dominating."
Giovino now runs the University at Buffalo's Department of Community Health and Health Behavior in Buffalo, New York.
The study, conducted between 2008 and 2010, found that across 14 developing nations, 49% of men and 11% of women used tobacco. Most of them smoked -- 41% of men and 5% of women.
Numbers were highest in Russia, where 60% of men and 22% of women used tobacco; China, where 53% of men and 2% of women were tobacco users; Ukraine, where 50% of men and 11% of women used tobacco, and Turkey, where 48% of men and 15% of women used tobacco.
In some countries, smoking rates may now be even higher than they were in 2010, WHO officials say.
"One place where we know it's gone up, unfortunately, is Egypt -- as a result of the revolution," said Edouard Tursan D'Espaignet of WHO''s tobacco control program.
The GATS study found 38% of men and less than 1% of women smoked in Egypt as of 2010.
However, government regulations limiting smoking in certain places fell apart after Hosni Mubarak's regime was ousted last year, and "the tobacco industry walked in very, very aggressively" to market its product amid the chaos, said Tursan D'Espaignet.
"We are hearing things like 'Smoking is a way to show you're free from the previous regime,'" he said.
The other nations in the new study are India, Bangladesh, Vietnam, the Philippines, Thailand, Poland, Brazil, Mexico, and Uruguay.
In general, marketing is a central reason smoking is on the rise in poorer nations, says Tursan D'Espaignet.
"In many countries, particularly eastern Europe and China, the market is probably saturated" among men, he said. "We can see the tobacco industry is targeting young people, and they're targeting women."
While previous studies done in several countries found that women who smoke generally start later than men, the GATS study found the opposite. "Alarmingly, this study shows that -- in most countries we surveyed -- age of smoking initiation for women might now be approaching the young ages at which men begin," the report says.
Still, the overwhelming majority of tobacco use worldwide is by men.
"Industry marketing campaigns traditionally have targeted men," says Giovino. Also, "social norms tend to make smoking socially less acceptable -- and even unacceptable in many countries -- among women."
But tobacco companies have succeeded in breaking those norms in some Western nations, and are trying to do so in low- and middle-income countries, he said.
Big tobacco is also extending its reach into new markets, such as Africa, Tursan D'Espaignet said.
Countries with weaker or poorer governments have a tougher time implementing the steps it takes to stop the spread of smoking.
Tobacco companies are "targeting countries that have less capacity to withstand the onslaught," said Tursan D'Espaignet.
Phillip Morris International, one of the world' s biggest tobacco companies, gave CNN a statement saying tobacco products "are generally subject to extensive regulation," including in Egypt, where its products have been sold since 1975.
The company also emphasized that it "is firmly opposed to smoking by minors."
Imperial Tobacco, another giant in the industry, said in a statement, "We seek opportunities to develop our business in existing markets worldwide where there's a legitimate demand for our products. We sell our products in accordance with local market regulations and our own international marketing standards. We employ the same responsible standards in our operations in Africa and Asia, for instance, as we do in any Western market.
"The risks associated with smoking are well known worldwide and enable people to choose whether or not to smoke."
The company added that its presence in Egypt is "negligible."
British American Tobacco and Japan Tobacco, the other two of the so-called "big four," did not immediately respond to requests for comment. Neither did the Tobacco Information Service, which functions as a trade association.
The WHO's Framework Convention on Tobacco Control, which opened for signature in 2003 and has been adapted by more than 170 countries, has led to "some very, very strong measures for tobacco control around the world," Tursan D'Espaignet said.
The framework calls for taxes to reduce tobacco sales, regulations limiting where smoking can take place, tough rules on labeling and packaging, and numerous other steps.
The GATS study included the latest figures from national studies done in the United States and Britain, in order to show a contrast between the industrialized world and developing nations.
In the United States, 19% of adults are smokers, a number that has been steadily decreasing, according to the CDC.
A new report published this week by U.S. Health and Human Services Secretary Kathleen Sebelius and Assistant Secretary for Health Dr. Howard Koh notes that smoking has dropped from 43% of the U.S. adult population in 1964. But tobacco dependence still causes more than 440,000 deaths in the United States each year.
"Furthermore, the marked slowing of declines in adult smoking prevalence over the past decade creates a renewed sense of urgency. It is time to reaffirm the commitment to ending the tobacco epidemic," says the Sebelius-Koh report, published in the Journal of the American Medical Association.
When it comes to youth smoking in the United States, the rate of decline has basically stopped over the last couple of years, according to a new study from the CDC.
It's a reflection of "a disturbing decline in state investments in comprehensive tobacco controlling programs," a CDC official told Time.
Still, the WHO's Tursan D'Espaignet says the United States is "taking strong measures" to cut smoking rates -- despite the fact that the U.S. government has not ratified the international framework convention.
In their report, Sebelius and Koh note than in 2009, the government directed $200 million in stimulus funds to support local anti-tobacco initiatives, and in 2011 the CDC awarded more than $100 million for tobacco control and other wellness programs.
In several nations, efforts to get smokers to quit are showing a great deal of success.
One showing "enormous reductions" is Australia, says Tursan D'Espaignet.
This week, Australia's high court upheld a rule that tobacco products must be in plain packaging without logos and bear graphic health warnings.
Other success stories include New Zealand, Ireland, and Britain, said Tusan D'Espaignet. Two of the countries in the new GATS study -- Turkey and Uruguay -- are also showing improvement due to such measures, he said.
The study got some of its funding from New York Mayor Michael Bloomberg's philanthropy, as well as the Bill and Melinda Gates foundation.
Bloomberg Philanthropies says that in 2007, it supported the WHO's efforts "to package and promote six proven policies to reduce tobacco use worldwide. These strategies -- including protecting people from tobacco smoke, offering help to quit, raising awareness about the dangers of tobacco through warning labels and public education campaigns, enforcing tobacco advertising bans, and raising the price of tobacco products -- are proven to reduce smoking rates. "
Since that initiative began in 2007, "21 countries have passed 100% smoke-free laws, the percentage of people protected from second-hand smoke has increased 400%, and almost four billion people worldwide are now protected by at least one of the six proven tobacco control policies," the group said.