Carl E. Bartecchi, Thomas D. MacKenzie, Robert W. Schrier
It has been 30 years since the surgeon general of the United States released the first report of the Advisory Committee on Smoking and Health. In each of the subsequent reports, cigarette smoking has been identified as the most important source of preventable morbidity and premature mortality in the United States. A total of 418,690 deaths in the United States were attributed to smoking in 1990 . That figure included approximately twice as many male as female smokers. Of the 2,148,000 U.S. residents who died in 1990, approximately half died of particular preventable causes. The prominence of tobacco as a contributor to mortality prompted former Surgeon General C. Everett Koop to state that cigarette smoking is the leading cause of preventable premature death in our society and the most important public health issue of our time.
The importance of focusing on cigarette smoking in 1994 has recently been underscored by data showing that the prevalence of smoking among adults in the United States, which had been declining annually since 1973, was unchanged at 25.7 percent from 1990 to 1991 . This occurred despite increasing evidence associating smoking with disease and death.
Currently 46.3 million adults (25.7 percent of the population) are smokers . This includes 24 million men (28.1 percent of the total) and more than 22 million women (23.5 percent). The prevalence is highest among persons 25 to 44 years of age. The percentage of smokers who report that they are heavy smokers (20 or more cigarettes per day) has changed little, from 26.0 percent in 1974 to 27.1 percent in 1985 .
In 1990 in the United States, smoking-related illnesses accounted for nearly one in five deaths and more than one quarter of all deaths among those 35 to 64 years of age . . Peto et al. have estimated that during the 1990s in developed countries, tobacco will cause approximately 30 percent of all deaths among those 35 to 69 years of age, making it the largest single cause of premature death in the developed world.
Though the emphasis of this review will be on cigarettes, the hazards of other tobacco products should not be overlooked. Despite declining consumption of these products , they continue to play an important part in morbidity and mortality in this country .
In viewing the problems and complications related to tobacco use, recognition of the contributions of passive smoking is increasing, as described in a 1992 report by the Environmental Protection Agency (EPA) . Reports indicate that environmental tobacco smoke is composed of mainstream smoke exhaled by the smoker and sidestream smoke emitted from the burning tobacco between puffs . Sidestream smoke is the main component of environmental tobacco smoke. The great majority of smoke emitted from a lit cigarette is sidestream smoke rather than smoke that is actively inhaled. Sidestream and mainstream smoke contain many of the same air contaminants. Sidestream smoke has more particles with smaller diameters, and these particles are therefore more likely to be deposited in the most distant regions of the lungs . Environmental tobacco smoke is a major source of indoor-air contaminants, and thus some unintentional inhalation by nonsmokers is virtually unavoidable. Since there appears to be no evidence of a safe threshold level, nonsmokers exposed to environmental tobacco smoke appear to be at increased risk for the same problems and complications recognized in smokers. Environmental tobacco smoke has been classified as a known human lung carcinogen, or a "group A" carcinogen, under the EPA's system of carcinogen classification.
A relation between cigarette smoking and coronary heart disease was reported by researchers at the Mayo Clinic in 1940 . Since that time, it has been well documented that cigarette smoking substantially increases the risk of cardiovascular disease, including stroke, sudden death, heart attack, peripheral vascular disease, and aortic aneurysm . In the United States in 1990, smoking caused 179,820 deaths from cardiovascular disease, accounting for 98,921 deaths from ischemic heart disease and 23,281 deaths from cerebrovascular diseases . Actually, a 10.4 percent decline in deaths from cardiovascular disease was noted in 1990 as compared with 1988.
The Office of Technology Assessment estimates that nearly one fifth of deaths due to cardiovascular disease in 1990 were attributable to smoking . In a study of British doctors, a strong dose-response relation was observed between the duration and extent of smoking and the death rate from ischemic heart disease among men younger than 65 years . Similar trends have been found in studies of women who smoke. The Nurses' Health Study showed that women who smoked one to four cigarettes per day had a 2.5-fold increased risk of fatal coronary heart disease and nonfatal myocardial infarction.
Components of cigarette smoke have been shown to damage vascular endothelium, and endothelial injury is considered a primary antecedent to atherosclerosis . The adverse effects of smoking are also related to its effects on coronary vaso-occlusive factors, such as platelet aggregation, vasomotor reactivity, and a prothrombotic state, and factors such as carbon monoxide production, increased plasma viscosity, and fibrinogen levels . Smoking is a major risk factor for coronary vasospasm . Smoking a single cigarette can cause profound silent disturbances in regional coronary blood flow in patients with angina and coronary artery disease . A study using ambulatory electrocardiographic monitoring detected 33 percent more episodes of ischemia per day and a significantly longer duration of ischemia in smoking as compared with nonsmoking patients with coronary heart disease. Cigarette smoking can also affect the vulnerability of the myocardium to ventricular fibrillation and cardiac arrest in patients with established coronary heart disease .
Numerous studies have reported elevated total plasma cholesterol concentrations and reduced high-density lipoprotein cholesterol concentrations in smokers, with the degree of alteration being associated with the number of cigarettes smoked per day. There is also strong evidence that cigarette smoking increases the risk of stroke and that there is a dose-response relation . Smokers have a risk of cerebrovascular disease that is 1.5 to 3 times that observed in nonsmokers . A study of identical twins discordant for cigarette smoking found that the total area of carotid plaques was 2.3 times larger in the smoking twins than in their nonsmoking siblings. Studies have shown that quitting smoking can greatly reduce the incidence of cardiac disease and death from coronary heart disease.
Recent reviews outline the relation of passive smoking to heart disease. Of the estimated 53,000 deaths caused by passive smoking each year in the United States, 37,000 have been attributed to heart disease. Glantz and Parmley's analysis of 10 epidemiologic studies indicates a significant dose-response effect related to passive exposure and suggests that nonsmokers living with smokers have a 30 percent increase in the risk of death from ischemic heart disease or myocardial infarction. Patients with angina pectoris have a reduction of 20 to 40 percent in exercise capacity after exposure to environmental tobacco smoke . Vasoconstriction from passively inhaled sidestream smoke is even more pronounced than that from mainstream smoke . In addition, more carbon monoxide, with its potential to reduce the oxygen-carrying capacity of the blood, is generated while a cigarette is smoldering than while it is being actively smoked .
In addition to being responsible for over 85 percent of lung cancers, smoking is also associated with cancers of the mouth, pharynx, larynx, esophagus, stomach, pancreas, uterine cervix, kidney, ureter, and bladder and accounts for about 30 percent of all deaths from cancer . The overall rates of death from cancer are twice as high among smokers as among nonsmokers; heavier smokers have rates that are four times greater. Cigarette smoking is undoubtedly the most important preventable cause of cancer in the United States today.
Rosenow estimated that 175,000 new cases of lung cancer would occur in 1993. The rates of lung cancer have increased dramatically over the past 60 years in association with increases in the number of cigarettes smoked; there is no evidence of a threshold level of exposure. The EPA study points out that active smoking increases the risk of all four major histologic types of human lung cancer and estimates that environmental tobacco smoke is responsible for about 3000 deaths from lung cancer annually. The report also notes that condensates of mainstream smoke or sidestream smoke that are suspended in acetone and applied to the skin of mice for long periods cause papillomas or carcinomas at the site of application. The study concludes from these studies and from the fact that the risk of lung cancer increases with younger ages at the initiation of smoking and decreases with longer times since cessation of smoking that tobacco smoke has both tumor-initiating and tumor-promoting capabilities. It also concludes, from several different analyses, including that of Fontham et al., that exposure to environmental tobacco smoke from spousal smoking is associated with increased mortality from lung cancer. A recent autopsy study of patients who died of causes other than respiratory diseases found an increase in "epithelial, possible precancerous lesions" in the lungs of nonsmoking women married to smokers. An important case-control study suggested that 17 percent of the cases of lung cancer among nonsmokers can be attributed to exposure to high levels of tobacco smoke during childhood and adolescence.
It is estimated that 82 percent of laryngeal cancers are due to cigarette smoking . The incidence of oral cancer among smokers ranges from 2 to 18 times that among people who have never smoked . Oral cancers include cancers of the tongue, salivary gland, mouth, lip, and pharynx. About 93 percent of oral-cavity tumors in men and 61 percent of such cancers in women are related to tobacco use, the greatest risk being in tobacco users who regularly use alcohol . The combination of smoking and alcohol use accounts for about three fourths of all oral and pharyngeal cancers . Studies have also conclusively established the use of smokeless tobacco as a cause of oral cancer . A recent monograph notes that 28 tumorigenic agents have been isolated and identified in smokeless-tobacco products and emphasizes that the nicotine in smokeless tobacco may also have a role as a potentiator in the carcinogenic process.
Of the estimated 10,200 deaths from cancer of the esophagus in 1993, about 80 percent can be attributed to cigarette smoking . The use of alcohol again increases the risk of the development of this cancer. Newcomb and Carbone suggested that contact carcinogenesis is the most likely pathogenetic mechanism for this cancer. Smoke constituents condense on the mucous membranes of the mouth and pharynx and are then swallowed.
Cancers of the hematopoietic system have been linked to cigarette smoking ; for example, 14 percent of all leukemias may be due to smoking . Cigarette smoke contains benzene, which has been linked with leukemia in the past. It has been suggested that a typical smoker inhales about 10 times as much benzene as a nonsmoker.
Cigarette smoking is thought to account for about 30 percent of the 13,500 new cases of cervical cancer estimated to have occurred in the United States in 1993 . Studies have linked cancer of the cervix to exposure to both mainstream and sidestream smoke. Various materials found in tobacco smoke, some with mutagenic activity, can be found in the cervical mucus of smokers.
Cigarette smoking is the leading cause of pulmonary illness and death in the United States . In 1990, smoking caused 84,475 deaths from pulmonary disease, mainly due to such problems as pneumonia, influenza, bronchitis, emphysema, and chronic airway obstruction . Chronic bronchitis and emphysema are the most important factors, according to a study of mortality rates among male British physicians. McCusker describes cigarette smoking as a chronic inflammatory disorder of the lower airways. Studies have shown a decline in pulmonary function in nonsmoking subjects with asthma after a controlled challenge of environmental tobacco smoke.
An estimated 6 million teenagers and another 100,000 youngsters under 13 years old smoke. Tobacco smoke creates major problems in early life and even in the fetus . The damage induced by the toxins in cigarette smoke during those most vulnerable periods when the lung is undergoing growth and remodeling has important implications for later life . A recent report noted that miscarriages of viable fetuses are increased in smokers and that babies born to mothers who smoke weigh an average of 200 g less than infants born to nonsmokers. Paternal smoking can also decrease birth weights in infants. The same report states that stillbirths and early neonatal deaths are increased by about 33 percent in the babies of smokers as compared with those of nonsmokers and that the effects of smoking in pregnancy extend well beyond infancy, with a reduction in growth and educational achievement.
Cotinine, a metabolite of nicotine, can be easily and accurately measured in saliva, blood, hair, and urine and serves as an indicator of exposure to tobacco smoke and smokeless tobacco . A finding of cotinine in the fetus supports the presence of the constituents of cigarette smoke in the fetus and indicates the degree of exposure to these elements.
The EPA report also reviews studies claiming that exposure to environmental tobacco smoke is causally associated with an increased risk of lower respiratory tract infections such as bronchitis and pneumonia in children, causing 150,000 to 300,000 cases annually in infants and young children up to 18 months of age. It notes that exposure to environmental tobacco smoke is associated with an increased prevalence of fluid in the middle ear, symptoms of upper respiratory tract irritation, and a small but significant reduction in lung function. The report also points out that exposure to environmental tobacco smoke is associated with additional episodes of asthma and increased severity of symptoms in children with asthma. The EPA report estimates that the condition of 200,000 to 1 million children with asthma in this country is worsened by exposure to environmental tobacco smoke and that such exposure is a risk factor for new cases of asthma in children. Mothers who smoke 10 or more cigarettes a day can cause as many as 26,000 new cases of asthma among their children each year. The EPA report reviews studies showing that infants of mothers who smoke are at increased risk of sudden infant death syndrome during the first year of life.
Our society is becoming increasingly concerned about the numbers of young people who smoke or use smokeless tobacco. Very few people begin smoking after reaching adulthood. In the United States, approximately 80 to 90 percent of smokers begin smoking before the age of 21, and an estimated 3000 teenagers start smoking each day . Teenage smokers smoke about 0.6 pack per day, or about 1.1 billion packs of cigarettes a year .
Academic performance and the level of educational achievement have predictive value in determining whether a person will become a smoker. The Centers for Disease Control and Prevention reported that in 1991 the prevalence of smoking ranged from 32 percent among the least educated to 13.6 percent among the most educated.
The health problems of children who smoke are summarized in the report of the Royal College of Physicians. In addition to the previously reviewed and the more obvious problems that would be expected from the early initiation and continuation of the smoking habit, the report noted that subarachnoid hemorrhage is six times more common in young smokers than in nonsmokers. Young people can be exposed to sidestream smoke and its serious consequences in multiple settings, such as in the home, in automobiles, at day care, at work, and unfortunately, even at school.
The use of smokeless tobacco, which includes both chewing tobacco and snuff, is increasing throughout the United States, especially among our most vulnerable population -- our children . Along with other forms of tobacco, it is a strong contributor to the 29,800 new cases of oral cancer that were projected to occur in 1993 . Surveys reveal that in 1988, 25.8 percent of boys between the ages of 12 and 17 had tried some form of smokeless tobacco. Although previously little use of smokeless tobacco was seen among adolescents, the prevalence of its use among older teens increased by 250 to 300 percent between 1970 and 1985 . The problems associated with the use of smokeless tobacco reinforce the conclusion of the 1986 Report of the Surgeon General that "there is no safe form of tobacco use" .
As of 1991, 23.5 percent of women were reported to be smokers . Fielding points out that today's female smokers are beginning at a younger age and are heavier smokers than in the past. The percentage of female smokers who smoke more than 25 cigarettes per day has almost doubled, from 13 percent in 1965 to 23 percent in 1985 . More young women than young men smoke today, and this is especially notable among high-school seniors . Also, in this time of declining prevalence of smoking, the rate of decline has been four times greater for men than for women and the rate of decline of smoking initiation among men was more than three times that observed for women .
Lung cancer, which caused an estimated 56,000 deaths in 1993, has surpassed breast cancer, which caused an estimated 46,000 deaths, as the most important cause of death from cancer among women . A study of more than 119,000 nurses, who were 30 to 55 years of age, over a six-year period confirmed the increased risk of fatal and nonfatal coronary events in female smokers. The heaviest smokers (more than 45 cigarettes per day) had 11 times the risk of women who had never smoked.
Women who take oral contraceptives and smoke are at considerably greater risk of dying of cardiovascular disease than are women who never use the pill or smoke . Female smokers are at greater risk for postmenopausal osteoporosis; an antiestrogen effect of smoking has been postulated to explain this complication . Fielding notes that smoking reduces fertility, increases the rate of spontaneous abortion, and increases the incidence of abruptio placentae, placenta previa, bleeding during pregnancy, and premature rupture of the placental membranes. These effects of smoking are thought to result in many thousands of preventable fetal and neonatal deaths .
A study by Colditz et al. found evidence of a strong causal relation between cigarette smoking and stroke among young and middle-aged women. In that study, as compared with women who had never smoked, women who smoked 1 to 14 cigarettes per day had an age-adjusted relative risk of stroke of 2.2, whereas those who smoked 25 or more cigarettes per day had a relative risk of 3.7.
In 1991, 31.4 percent of Native Americans and Alaska Natives, 29.2 percent of blacks (35.1 percent of black men), and 20.2 percent of Hispanics smoked . The lowest rate -- 15.5 percent -- was among Hispanic women. One study showed that only 2.8 percent of Hispanics and 2.5 percent of blacks, as compared with 8.9 percent of whites, were likely to be heavy smokers (to smoke more than 25 cigarettes daily). The prevalence of smoking and the rates at which people began to smoke or quit smoking changed in a similar manner among blacks and whites from 1974 to 1985 . More black and Hispanic men than black and Hispanic women begin to smoke during childhood and adolescence .
Problems related to the high prevalence of smoking among black men are reflected in a 1993 report of age-adjusted death rates per 100,000 population for selected smoking-related cancers (those of the lung, oral cavity, and pharynx, esophagus, and larynx); in each case, black men had the highest death rate. An increased incidence of tobacco-related disease has been noted among Native Americans . This increase was recognized in the mid-1970s to be due to the increase in daily cigarette smoking in this group.
In the U.S. population over the age of 65, it has been reported that the percentage of smokers is lowest among Hispanic women (10 percent) and highest among black men (31.1 percent). The same report pointed out that in the group over 65 years of age, 6.9 percent of the men used smokeless tobacco (snuff, chewing tobacco, or both). Oral cancers from smokeless tobacco typically occur in these men (median age at diagnosis, 62.4 years) . A prospective study suggests that the hazards of smoking extend well into later life. Among men and women over 65 years of age, the rates of total mortality among current smokers were twice what they were among participants who had never smoked.
Strokes are an especially important problem for the elderly. Among those over the age of 65, 24 percent of cerebrovascular disease in men (6 percent in women) was attributable to smoking . Another study suggests a causal relation between smoking and hypertension and subarachnoid hemorrhage, an especially disabling and lethal form of cerebrovascular disease.
Of concern to all smokers, young and old, are recent data that suggest a potential role of cigarette smoking in the development of cataracts. Studies suggest that about 20 percent of cataracts are attributable to smoking in the United States .
Statistically, women in this country have lived longer than men in the 20th century . Fielding notes that "the difference in longevity that leads so many women to survive their male contemporaries is being abridged by an increase in the number of women who fall victim to their most deleterious habit -- smoking."
© 1999 Last updated on December, the 11th, 1999.
En son 11 Aralık 1999'da yenilendi
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