The leaves of the tobacco plant were originally harvested and smoked by Native Americans and were introduced to Europe by Christopher Columbus in the 15th century. The botanical name for tobacco, Nicotiana tabacum, is derived from the Jean Nicot, who sent the tobacco leaf to the Queen of France in the 16th century. During the late 18th century, packaged cigarettes and cigars rapidly gained popularity. Although it was suspected in the early 20th century that tobacco was linked to throat and mouth cancers, it was not until 1964 when the US government released the document titled Smoking and Health: Report of the Advisory Committee to the Surgeon General of the Public Health Service. It has since been the prominent topic of most annual Surgeon Generals Reports.
The original report was an objective review of literature that pointed to tobacco use as being causal to a number of deleterious health conditions. There has since been much research conducted, and many new findings regarding the disease-causing aspects of tobacco smoking have been elucidated. Despite the widely published results of this research tobacco smoking-related illnesses remain the leading cause of preventable death in the United States.
About 23% of the worldwide population smokes cigarettes. This includes 32% of all males and 7% of all women. Eastern and Southeast Asia have the highest prevalence of smokers in the world with about 45%, while the Caribbean and North American has the lowest prevalence at 20%.
In 2017, the CDC estimates that 19.3% of the United States population over 18 years old uses some tobacco product. About 14% of the total population use cigarettes while the remaining 5% use cigars, electronic cigarettes, smokeless tobacco, or pipes. Furthermore, 24.8% of men smoke cigarettes, while 14.2% of women smoke cigarettes. By age group, smokers represent 18.3% of adults aged 18 to 24 years old, 22.5% of adults aged 25 to 44 years old, 21.3% of adults aged 45 to 64 years old and 11% of adults 65% and older.
Although some of the exact mechanisms for tobacco smoking (TS)-related illnesses have yet to be elucidated, several studies have linked TS to a plethora of devastating illnesses including coronary artery disease (CAD), cancers in every human organ system, chronic obstructive pulmonary disease (COPD), and decreased reproductive health. 
Several potential mechanisms have been described linking TS with CAD. TS increases the amount of exogenous and endogenous free radicals in the body, leading to an increased amount of oxidative stress. This increased oxidative stress leads to vasomotor dysfunction, increased pro-thrombotic and decreased fibrinolytic factors, leukocyte, and platelet activation, increased lipid peroxidation, increased adhesion and inflammatory molecules, and smooth muscle proliferation. Researchers postulate that a combination of these factors leads to the development of CAD in tobacco smokers.
TS has been associated with an increased risk of developing at least 17 classes of human cancers. There are roughly 60 known cancer-causing molecules, called carcinogens, in tobacco smoke. It has been proposed that these carcinogens directly damage the DNA by forming covalent bonds with DNA, forming molecules called DNA adducts. These DNA adducts are damaged pieces of DNA that, if not repaired properly, cause mutations during cellular division when their reproduction results in a mutated copy of the DNA. Over time, these mutations collectively lead to disruption of the normal cell reproductive cycle leading to neoplastic tumor formation.
Chronic obstructive pulmonary disease (COPD) has also been shown to be heavily associated with TS. The reactive oxidants found with cigarette smoke create a chronic inflammatory state in the lungs, which may persist even after smoking cessation. This inflammatory state causes the lungs to remodel and can eventually lead to gross structural changes. It has also been proposed that there is an auto-immune component to lung disease, caused by the reaction of auto-antibodies to antigens created either directly or indirectly from TS.
TS has several deleterious effects on human reproductive health. In men, smoking has been linked to decreased semen volume, decreased sperm density, and decreased total sperm count. In women, TS has been shown to disrupt the normal menstruation cycle and decrease ovarian reserve. TS while pregnant is also associated with low birth weight and cryptorchidism.
Tobacco smoke is comprised of a mixture of more than 4000 different compounds. Mainstream smoke, which is the smoke directly inhaled from the end of the cigarette into the smoker’s lungs, is hotter, denser, and contains more compounds than the sidestream smoke that emanates from the lit end of the cigarette. Mainstream smoke is the most type dangerous type of cigarette smoke although sidestream smoke has also been linked to significant illnesses. Many of the molecular compounds found in TS form via the process of combustion as the cigarette burns between 600 F and 900 F. After smoke is drawn from the cigarette, the particles rapidly increase in size due to humidification from the moist air in the upper respiratory tract. The mainstream smoke subsequently condenses as it heads into the lungs, leaving an estimated 50% to 95% of these molecules deposited into the bronchi, bronchioles, and alveoli.
TS history should be routinely obtained from the patient while taking the social history. Pack-year history provides an estimate the amount cigarettes a patient has consumed over a lifetime and is calculated as packs smoked per day multiplied by the total number of years smoked. Obtaining a pack-year history has shown to be of some value when determining the presence and severity of smoking-related illnesses such as CAD and COPD, as smoking-related cancers have all been linked to increased pack-year history.
Many physical exam findings can be directly or indirectly related to tobacco smoking. On exam of the oropharynx, periodontal disease, tooth loss, and cancers of the tongue and oropharynx may be visualized. The scent of tobacco smoke often lingers on the patient's breath and clothing. Auscultation of the lungs may reveal decreased or asynchronous breath sounds. Cardiac exam often reveals an increased resting heart rate when compared to that of non-smokers. Tobacco stains may be present on the skin of the face and fingers. There may be decreased peripheral pulses due to smoking-related peripheral vascular disease.
Tobacco smoking is directly associated with multiple serious health problems that endanger and shorten the life of smokers and those subjected to cigarette smoke. For an active smoker, quitting smoking has proven to reduce the chances of developing a smoking-related illness.
Daily cigarette smokers keep smoking because they are physically addicted to nicotine - a substance that is naturally found in tobacco leaves. Because nicotine is one of the most addictive substances known to man, TS is often very difficult to quit, often requiring repeated attempts at quitting involving various cessation methods. Five nicotine-based medications (gum, lozenges, inhaler, nasal spray, patch) and 2 non-nicotine-based medications (varenicline and bupropion SR) have been shown to aid in long-term smoking cessation. Recent evidence includes a potential role for cytisine and naltrexone. For patients willing to quit, a combination of counseling and one or more the medications has proven more effective than just counseling or medication alone.
Tobacco smoking is extremely hazardous to human health. For smokers, the rate of death from any cause is about 3-times those who have never smoked. The excess mortality of smokers is mostly attributed to vascular illness such as CAD, respiratory illnesses such as COPD, at least 17 different classes of tobacco-smoking related cancers. It has been demonstrated that smokers lose at least 10 years of life expectancy on average. Quitting smoking before the age of 40 has been shown to reduce smoking-related death by about 90% 
TS is a life-threatening addiction that, if untreated, can cause damage to every organ system in the human body. The best way to avoid a TS related illness is never to start smoking, and the second best way is to stop smoking cigarettes as soon as possible. Helping a patient to stop smoking is one of the most beneficial preventive medicine interventions currently in existence. Nearly every member of the healthcare team may play an important role in the assistance of smoking cessation.
Nurses play a large role in tobacco cessation programs. In some hospitals, nurses are being trained to deliver behavioral and pharmaceutical interventions to inpatient smokers. These interventions have shown great promise in significantly reducing smoking in certain populations.
Physicians are also at the front lines in the fight against TS. Unfortunately, several studies have shown that brief episodes of physician advice do very little to aid in smoking cessation. It has been demonstrated that individually focused counseling, when delivered by a physician, can aid in the patient's cessation of smoking. There is also evidence that physician prescribed or physician recommended over-the-counter medications can play an effective role in treating these patients.
Clinical scientists also play a very important role in the fight to end tobacco addiction and tobacco-related disease. They continue to investigate and discover the physiology of tobacco-related illnesses, the effectiveness of tobacco cessation medications and interventions, and study TS related conditions across a broad spectrum of populations. From the toils of scientific research, much about TS has been elucidated and yet we as a society have much to learn.
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