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Prevalence - Smoking
Tobacco may be consumed by either smoking or other smokeless methods such as chewing, the World Health Organization (WHO) only collect data on smoked tobacco. Smoking has therefore been studied more extensively than any other form of consumption.
In 2000, smoking was practiced by 1.22 billion people, predicted to rise to 1.45 billion people in 2010 and 1.5 to 1.9 billion by 2025. If prevalence had decreased by 2% a year since 2000 this figure would have been 1.3 billion in 2010 and 2025. Despite dropping by 0.4 percent from 2009 to 2010, the United States still reports an average of 17.9 percent usage.
Smoking is generally five times more prevalent among males than females, however the gender gap declines with younger age. In developed countries smoking rates for men have peaked and have begun to decline, however for women they continue to climb.
As of 2002, about twenty percent of young teens (13–15) smoke worldwide, with 80,000 to 100,000 children taking up the habit every day—roughly half of whom live in Asia. Half of those who begin smoking in adolescent years are projected to go on to smoke for 15 to 20 years.
The WHO states that "Much of the disease burden and premature mortality attributable to tobacco use disproportionately affect the poor". Of the 1.22 billion smokers, 1 billion of them live in developing or transitional nations. Rates of smoking have leveled off or declined in the developed world. In the developing world, however, tobacco consumption is rising by 3.4% per year as of 2002.
The WHO in 2004 projected 58.8 million deaths to occur globally, from which 5.4 million are tobacco-attributed, and 4.9 million as of 2007. As of 2002, 70% of the deaths are in developing countries.
The shift in prevalence of tobacco smoking to a younger demographic, mainly in the developing world, can be attributed to several factors. The tobacco industry spends up to $12.5 billion dollars annually on advertising, which is increasingly geared towards adolescents in the developing world because they are a very vulnerable audience for the marketing campaigns. Adolescents have more difficulty understanding the long term health risks that are associated with smoking and are also more easily influenced by “images of romance, success, sophistication, popularity, and adventure which advertising suggests they could achieve through the consumption of cigarettes”. This shift in marketing towards adolescents and even children in the tobacco industry is debilitating to organizations’ and countries’ efforts to improve child health and mortality in the developing world. It reverses or halts the effects of the work that has been done to improve health care in these countries, and although smoking is deemed as a “voluntary” health risk, the marketing of tobacco towards very impressionable adolescents in the developing world makes it less of a voluntary action and more of an inevitable shift.
In the 1930s German scientists showed that cigarette smoking caused lung cancer. In 1938 a study by a Johns Hopkins University scientist suggested a strongly negative correlation between smoking and lifespan. In 1950 five studies were published in which "smoking was powerfully implicated in the causation of lung cancer". These included the now classic paper "Smoking and Carcinoma of the Lung" which appeared in the British Medical Journal. This paper reported that "heavy smokers were fifty times as likely as non-smokers to contract lung cancer".
In 1953 scientists at the Sloan-Kettering Institute in New York City demonstrated that cigarette tar painted on the skin of mice caused fatal cancers. This work attracted much media attention; the New York Times and Life both covered the issue. The Reader's Digest published an article entitled "Cancer by the Carton".
A team of British scientists headed by Richard Doll carried out a longitudinal study of 34,439 medical specialists from 1951 to 2001, generally called the "British Doctors Study." The study demonstrated that about half of the persistent cigarette smokers born in 1900–1909 were eventually killed by their habit (calculated from the logarithms of the probabilities of surviving from 35–70, 70–80, and 80–90) and about two thirds of the persistent cigarette smokers born in the 1920s would eventually be killed by their habit. After a ban on smoking in all enclosed public places was introduced in Scotland in March 2006, there was a 17 percent reduction in hospital admissions for acute coronary syndrome. 67% of the decrease occurred in non-smokers.
The health effects of tobacco have been significant for the development of the science of epidemiology. As the mechanism of carcinogenicity is radiomimetic or radiological, the effects are stochastic. Definite statements can be made only on the relative increased or decreased probabilities of contracting a given disease; Philosophically and theoretically speaking, it is impossible to definitively prove a direct causative link between exposure to a radiomimetic poison such as tobacco smoke and the cancer that follows. Tobacco companies have capitalized on this philosophical objection and exploited the doubts of clinicians, who consider only individual cases, on the causal link in the stochastic expression of the toxicity as actual disease.
There have been multiple court cases on the issue that tobacco companies have researched the health effects of tobacco, but suppressed the findings or formatted them to imply lessened or no hazard.
A study published in the journal Pediatrics refers to the danger posed by what the authors call "third-hand smoke" — toxic substances that remain in areas where smoking has recently occurred. The study was reviewed in an story broadcast by the Voice of America.
The term "smoker" is used to mean a person who habitually smokes tobacco on a daily basis. This category has been the focus of the vast majority of tobacco studies. However, the health effects of less-than-daily smoking are far less well understood. Studies have often taken the data of "occasional smokers" (those who have never smoked daily) and grouped them with those who have never smoked.
A recent European study on occasional smoking published findings that the risk of the major smoking-related cancers for occasional smokers was 1.24 times that of those who have never smoked at all but the result was not statistically significant. (For a confidence interval of 95%, this data showed an incidence rate ratio of 0.80 to 1.94.) This compares to studies showing that habitual heavy smokers have greater than 50 times the incidence of smoking-related cancers.