It is estimated that one third of the world’s adult population, and around 1.1 billion individuals, smokes tobacco, which makes every sixth human being a smoker. Smoking-related illness is estimated to cause ∼ 5 million deaths per annum around the globe, but is considered a leading preventable cause of death. In developed countries, the rates of smoking have either leveled off or declined, but smoking-related deaths are on the rise in developing countries and are most common among the least-educated people. Initially, cigarette smoking prevalence was higher in males, but since the 1980s the gender gap has narrowed and plateaued.
In 2003, in a school-based cross-sectional survey on water pipe-based tobacco smoking (sheesha) in Oman, 1,962 students were interviewed (26.6% were ever-smokers and 9.6% were current smokers). Among the current smokers, 15.5% were males and only 2.6% were females.4 In the USA in 2009, approximately 20.6% of adults and nearly 20% of high school students were cigarette smokers. An estimated 9% of them were smokeless tobacco consumers. Smokeless tobacco products include products such as moist snuff, chewing tobacco, snus (moist powdered tobacco) and dissolvable nicotine products such as strips and sticks. Current evidence, however, does not support the opinion that the use of these products is safer than smoking. Additionally, there is substantial evidence that these products can be implicated in oral and pancreatic cancers, precancerous oral lesions, gingival recession, gingival bone loss around the teeth, tooth-staining, and nicotine addiction.
In the USA, tobacco use is responsible for nearly 1 in 5 deaths. In 2012, the estimated percentage of new lung cancers in males (116,470 cases) and females (109,690 cases) was 14% each. Among these lung cancers, 29% of male and 26% of female cases were estimated to be fatal.3 Smoking accounts for at least 30% of all cancer deaths and 87% of lung cancer deaths.
Cases of small-cell lung carcinoma (SCLC) cancer in never-smokers are exceptionally rare. Active smoking also increases the risk of numerous other cancers, including those of the nasal passages, sinuses, oral cavity, and upper aero digestive tract, pancreas, gynecological system, kidney, and bladder, and stomach, colorectal and acute myeloid leukemia. The World Health Organization (WHO) has published guidelines to measure smoking, and classifies individuals as smokers, non-smokers, or ever-smokers, and then establishes further sub-categories.