The health effects of Smoking are the circumstances, mechanisms, and factors of tobacco consumption on human health. Epidemiological research has been focused primarily on cigarette tobacco smoking, which has been studied more extensively than any other form of consumption. Tobacco is the single greatest cause of preventable death globally.
Tobacco use leads most commonly to diseases affecting the heart, liver and lungs, with smoking being a major risk factor for heart attacks, strokes, chronic obstructive pulmonary disease (COPD) (including emphysema and chronic bronchitis), andcancer (particularly lung cancer, cancers of the larynx and mouth, and pancreatic cancer). It also causes peripheral vascular disease and hypertension.
The effects depend on the number of years that a person smokes and on how much the person smokes. Starting smoking earlier in life and smoking cigarettes higher in tar increases the risk of these diseases. Also, environmental tobacco smoke, or secondhand smoke, has been shown to cause adverse health effects in people of all ages. Cigarettes sold in underdeveloped countries tend to have higher tar content, and are less likely to be filtered, potentially increasing vulnerability to tobacco-related disease in these regions.
The World Health Organization (WHO) estimates that tobacco caused 5.4 million deaths in 2004 and 100 million deaths over the course of the 20th century. Similarly, the United States Centers for Disease Control and Prevention describes tobacco use as “the single most important preventable risk to human health in developed countries and an important cause of premature death worldwide.” Several countries have taken measures to control the consumption of tobacco with usage and sales restrictions as well aswarning messages printed on packaging. Smoke contains several carcinogenic pyrolytic products that bind to DNA and cause many genetic mutations. There are 45 known or suspected chemicalcarcinogens in cigarette smoke. Tobacco also contains nicotine, which is a highly addictive psychoactive drug.
When tobacco is smoked, nicotine causes physical and psychological dependency. Tobacco use is a significant factor in miscarriages among pregnant smokers, and it contributes to a number of other threats to the health of the fetus such as premature births and low birth weight and increases by 1.4 to 3 times the chance for Sudden Infant Death Syndrome (SIDS).
The result of scientific studies done in neonatal rats seems to indicate that exposure to cigarette smoke in the womb may reduce the fetal brain’s ability to recognize hypoxic conditions, thus increasing the chance of accidental asphyxiation. Incidence of impotence is approximately 85 percent higher in male smokers compared to non-smokers, and is a key factor causing erectile dysfunction (ED). Contents
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. In the 1930s German scientists showed that cigarette smoking caused lung cancer.:15 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.
TheReader’s Digest published an article entitled “Cancer by the Carton”.:14 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 addiction (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 addiction.
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; For a particular individual, it is impossible to definitively prove a direct causal link between exposure to a radiomimetic poison such as tobacco smoke and the cancer that follows; such statements can only be made at the aggregate population level. 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 2006 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.)
(Data reduction used Cox proportional hazard model, stratified by gender and country.) This compares to studies showing that habitual heavy smokers have greater than 50 times the incidence of smoking-related cancers. 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. 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.