Despite significant worldwide declines in smoking, close to a billion people still smoke tobacco products every day, according to an analysis from the Global Burden of Disease Study 2015.

One in four men and one in 20 women smoke daily, even though overall smoking rates declined by 28% among men and 34% among women from 1990 to 2015, researchers reported April 5 in The Lancet.

Moreover, deaths attributable to tobacco use increased by 4.7% globally despite the declining smoking rates, such that more than 10% of all deaths worldwide were associated with smoking, the report found.

Senior author Emmanuela Gakidou, PhD, of the University of Washington Institute for Health Metrics and Evaluation in Seattle told MedPage Today that while tobacco control programs have greatly contributed to global smoking declines, population growth has led to an increase in the number of smokers worldwide.

Gakidou and colleagues culled data from nearly 3,000 different sources to come up with the global estimates.

Worldwide, smoking prevalence decreased by almost a third (29.4%) from 1990 to 2015, when the smoking rate fell to 15.3%. But population growth drove the overall number of smokers up, from 870.4 million to 933.1 million during the period.

Gakidou said she believes complacency among policymakers and health officials may be preventing even greater progress in efforts to reduce or prevent smoking worldwide.

She said because smoking rates have been declining for years in many developed and developing countries, there is a sense that smoking is an issue that has been dealt with, even though it remains the second leading cause of death globally, after hypertension.

"What we are hoping to do with this study is the equivalent of screaming as loud as we can that smoking is still a huge global problem," she said. "We need to do much more."

The newly published smoking prevalence and harms estimates are derived from data from 195 countries and territories.

Gakidou said the World Health Organization's global anti-tobacco initiative Framework Convention on Tobacco Control (FCTC) has been a key driver of recent progress in reducing smoking prevalence in many regions of the world. Strategies identified and recommended under the global treaty for preventing and reducing smoking include taxing tobacco products, restricting advertising, and marketing and offering smoking cessation services.

She said several countries have gone above and beyond the recommendations of the FCTC.

"Brazil has been a huge success story," she said. "They have adopted the WHO FCTC and they have done much more than that. And smoking rates have declined from around 30% to around 10% today."

Despite the declines, Brazil remained among the top 10 countries with the largest number of smokers in 2015, along with China, India, Indonesia, the United States, Russia, Bangladesh, Japan, Germany and the Philippines.

Indonesia, Bangladesh and the Philippines saw no significant reductions in male smoking prevalence between 1990 and 2015, and female smoking prevalence actually increased in Russia during the same period, from 7.9% to 12.3%.

The global analysis also revealed that:

In 2015, the worldwide prevalence of daily smoking was 25.0% (95% uncertainty interval [UI] 24.2%-25.7%) for men and 5.4% (5.1%-5.7%) for women, representing 28.4% (25.8%-31.1%) and 34.4% (29.4%-38.6%) reductions, respectively, since 1990

More countries and territories achieved significant annualized rates of decline in smoking prevalence from 1990 to 2005 than in between 2005 and 2015; however, only four countries had significant annualized increases in smoking prevalence between 2005 and 2015 (Congo and Azerbaijan for men and Kuwait and Timor-Leste for women)

In 2015, 11.5% of global deaths (6.4 million, 95% UI 5.7-7.0 million) were attributable to smoking worldwide, of which 52.2% of deaths occurred in four countries (China, India, the United States, and Russia)

Smoking ranked among the five leading risk factors by disability-adjusted life years (DALY) in 109 countries and territories in 2015, rising from 88 in 1990

"Amid gains in tobacco control worldwide, smoking remains a leading risk factor for early death and disability," the report noted. "Although there have been some success stories, for many countries and territories, faster annualized rates of decline in smoking prevalence occurred between 1990 and 2005 than between 2005 and 2015.

Although smoking prevalence and risk-deleted DALY rates fell worldwide, population growth and aging ultimately offset these gains and contributed to overall increases in smoking-attributable disease burden.

"Intensified tobacco control and strengthened monitoring are required to further reduce smoking prevalence and attributable burden, especially in view of the fact that demographic factors like population aging are not easily amenable to intervention," the report concludes.