Overall prevalence of smoking has decreased globally, although number of smokers has increased

"Given the importance of tobacco as a risk to health, monitoring the distribution and intensity of tobacco use is critical for identifying priority areas for action and evaluating progress. Early efforts to estimate smoking prevalence were based on limited data for many developing countries," according to background information in the article. "Despite improvements in data availability, information on trends has not been synthesized in a systematic and consistent way."

Marie Ng, Ph.D., of the Institute for Health Metrics and Evaluation, University of Washington, Seattle, and colleagues conducted a study to estimate levels and trends in the prevalence of smoking by age and sex and consumption of cigarettes for 187 countries from 1980 to 2012. Nationally representative sources that measured tobacco use were systematically identified. Survey data that did not report daily tobacco smoking were adjusted using the average relationship between different definitions.

The researchers found that between 1980 and 2012, the estimated prevalence of daily tobacco smoking for men declined from 41 percent to 31 percent; for women, there was a decline from 10.6 percent to 6.2 percent. Global progress in reducing the prevalence of smokers appeared to fall into 3 phases for both men and women: modest progress from 1980 to 1996, followed by a decade of more rapid global progress, then a slowdown in reductions from 2006 to 2012, with an apparent increase since 2010 for men. This deceleration in the global trend was in part due to increases in the number of smokers since 2006 in several large countries including Bangladesh, China, Indonesia and Russia.

While prevalence declined, because of the growth in population older than 15 years of age, there has been a continuous increase in the number of men and women who smoke daily, increasing from 721 million in 1980 to 967 million in 2012, with a 41 percent increase in the number of male daily smokers and a 7 percent increase for female smokers. Between 1980 and 2012, the number of cigarettes consumed worldwide increased by 26 percent.

Prevalence rates exhibited substantial variation across age, sex, and countries, with rates below 5 percent for women in some African countries to more than 50 percent for men in countries such as Indonesia, Armenia, Laos, Papua New Guinea and Russia. The number of cigarettes per smoker per day also varied widely across countries.

"Although in several countries substantial uncertainty remains in monitoring tobacco exposure and estimating the disease burden associated with it, there can be no doubt that both are large. Policies and strategies to improve global health must include comprehensive efforts to control tobacco use, as envisaged under the Framework Convention on Tobacco Control. But implementation of policies is not enough; countries, and the global health community, need to collect timely, reliable, and detailed information on the effect of those policies, particularly among vulnerable populations and those being directly targeted by the tobacco industry. If global tobacco control is to benefit from concerted policy action, population-level surveillance of tobacco use and its health effects needs to be strengthened and routinely used to evaluate the impact of tobacco control strategies," the authors write.

"Although many countries have implemented control policies, intensified tobacco control efforts are particularly needed in countries where the number of smokers is increasing."