Worldwide cancer incidence and mortality reflects smoking prevalence, among other factors.
Worldwide 1 billion adults (800 million men and 200 million women) currently smoke cigarettes. This is an underestimate of total tobacco exposure worldwide, as it does not include childhood smoking, smokeless tobacco or second-hand smoke. Cigarette smoking prevalence varies widely around the world, and over 80% of the world's adult male smokers, and half of the world's adult female smokers, live in low- or middle-income countries.
Tobacco use kills almost 6 million people worldwide each year, with nearly 80% of these deaths in low- and middle-income countries. Each year 600,000 non-smokers worldwide die from exposure to environmental tobacco smoke. By 2030 tobacco will kill a predicted 8 million people worldwide each year. Tobacco use caused 100 million deaths worldwide during the 20th century, and if current trends continue it will kill 1 billion people in the 21st century.
Worldwide smoking prevalence is overall increasing. However, different countries are at different stages of their tobacco epidemic, a model in which smoking prevalence increases, stabilises and eventually decreases, and some decades later the proportion of tobacco-attributable deaths follows a related curve of increase, stability and decrease. Low- and middle-income countries are generally in the earlier stages, with smoking prevalence increasing, therefore the proportion of tobacco-attributable deaths in those countries is expected to increase; in contrast most high-income countries are in the later stages, with falling smoking prevalence and stabilising or falling proportion of tobacco-attributable deaths.