Tobacco Documents Online

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CHAPTER 2 EFFECTS OF SMOKING ON SMOKERS Donald Shopland Public Health Advisor Smoking, Tobacco, and Cancer Program National Cancer Institute, Bethesda, MD. Use of tobacco in the United States predates the arrival of Columbus and the early settlers. In the early part of the 16th century, soon after the introduction of tobacco into Spain and England by explorers returning from the New World, controversy developed from differing opinions as to the effects of human use of the leaf and products derived from it by combustion of other means. Pipe smoking, chewing, and snuffing (also dipping) of tobacco were praised for pleasurable and even reputed medicinal actions. Attempts aimed at controlling its use throughout the centuries proved useless--particularly when its control was based on moral and religious grounds. Even though tobacco use has been a part of the American culture for the better part of four centuries, the use of cigarettes has a much shorter history than that of other forms of tobacco consumed per adult, over 6 pounds, was in the form of chewing tobacco (4.1 lb), pipe tobacco (1.63 lb.), and snuff (0.32 lb.). Cigars and cigarettes accounted for the remaining pound of tobacco consumes, with cigars accounting for the larger proportion. As a nation,_the_U.S..._consumed.approximately 2.5 billion cigarettes annually or only about 54 cigarettes annually per person 18 years of age and older in 1900 (Figure 1). This pattern of tobacco use changed radically soon after 1910 with the introduction of the blended cigarette--demand accelerated as cigarette advertising and promotion became more aggressive. Male tobacco users changed from other forms of tobacco to cigarettes in a relatively short time period. By the end of the First World War, a majority of males had become cigarette smokers. In contrast, women did not take up cigarette smoking in large numbers until nearly 25 years later. Women, however, had never used other tobacco products (except for snuff) and few of the older age cohorts of women had ever been smokers. Thus compared to men who switched from other forms of tobacco, women 22

Generally, the number of years one has smoked and the inhalation patterns (Figure 7) ar also strongly correlated with increased lung cancer death rates in smokers compared to nonsmokers. In summary, the greater the life-term exposure to tobacco smoke, the greater the risk. When the agent is removed, for example if an individual quits smoking, their lung cancer risk begins to decline (Figure 8). This risk continues to decline relative to the continuing smoker an after about 15 years off cigarettes the former smoker's lung cancer risk begins to approximate that of the lift-long nonsmoker. However, it appears that some excess risk may be carried throughout life, although this risk is strongly influenced by the individual:s total life- time exposure to the agent and the total number of years of smoking cessation: Coronary Heart Disease Coronary heart disease (CHD) continued to be this nation's leading cause of death, and for nearly 20 years, medical research has shown that smoking is one of the major independent risk factors or causes of CHD (along with high blood pressure and high cholesterol levels). In the final report of the Pooling Project, an interaction between smoking and other risk factors was observed (Figure 9). Each independent risk factor contributed about the same increased level of risk, however, when two or more factors wee present, the risk of a major CHD event was increased beyond the sum of the independent risk--thus, a synergistic effect was created when two or more risk factors were present. The independent risk of CHD for smoking is greater at the younger age groups although the greatest number of excess CHD deaths due to smoking actually occurs in the older age groups (Figure 10). Smoking has also been shown to increase the risk for other cardiovascular diseases, including peripheral vascular disease, cerebrovascular-disease (at younger age groups), and aortic aneurysms. For women, smoking can interact with oral contraceptives to greatly increase the risk for fatal and nonfatal myocardial infarction and subarachnoid hemorrhage. Many public health estimates place the total number of excess cardiovascular disease deaths due to smoking to be greater than those due to cancer. Up to 30 percent of all CHD deaths may be due to cigarette smoking and its interaction with other risk factors. Chronic Obstructive Lung Disease While the number of deaths classified as chronic obstructive lung disease (COLD) are much smaller than those for cancer or 26

cardiovascular disease, COLD represents a group of diseases which affect millions of individuals. These diseases, which include emphysema, can be severely debilitating and represent a substantial number of people who become disabled due to their condition, unable to work or even seek employment. For many years cigarette smoking has been known to increase the risk of developing and dying from COLD. Even the first Surgeon Generals Report issued in 1964 identified a causative role between smoking and chronic bronchitis. As with lung cancer, the risk of contracting and dying from COLD is substantially elevated among smokers (Figure 11) and this risk increases with an increasing dose of cigarette smoke received. Mortality rations for COLD in smokers versus nonsmokers are very high, exceeding 30 to 1 for heavy smokers (Figure 12). Smoking also has a dramatic effect on lung function. The normal rate of lung function decline observed with increasing age is accelerated in cigarette smokers (Figure 13). While quitting smoking can reverse this decline so that the continuing decline resembles that of the nonsmoker, there is little evidence to suggest that former smokers regain any of the previously lost lung function. Lb 27 ~ GD O m N O ca

once they adopted tobacco use, were almost exclusively cigarette smokers. It is somewhat ironic that one of the reasons for the rapid switch from smokeless tobacco to cigarettes was out of concern for health . At the turn of the century, tuberculosis was still an uncontrolled disease, representing a major cause of early death nd disability. Some of the prevailing medical opinion of the day was that "spitting" spread the TB germ--thus public expectoration increasingly become socially unacceptable; and many localities passed ordinances prohibiting public spitting. this helped encourage the uptake of cigarettes by men who represented the major demographic group of tobacco users. When individual cohorts of men and women are examined, it is quite evident that each adopted smoking as a life-style at different rates. Peak life-time prevalence for males occurred among those cohorts born from 1900 through the 1930's (Figure 2) whereas among women peak prevalence did not occur until the appearance of cohorts born 1930 and thereafter (Figure 3). Some older age cohorts of inen had smoking prevalence which exceeded 80 percent--that is 80 percent or more had been regular smokers at some time during their life. No cohort of women ever achieved this high prevalence rate. The highest smoking rate observed for any cohort of women was around 50 percent ever smokers. Differences in uptake and use of cigarettes between men and women account for many of the differences observed for some smoking related cancers and other diseases related to cigarette and tobacco use. Substantial differences also exist with respect to their quitting behavior. In 1964, when the first Surgeon Generals Report on Smoking and Health was published, over half of all males (53 percent) were regular cigarette smokers; compared to only on-third of women (34 percent). (In 1955 over 50 percent of males were regular smokers, but smoking by women was only half that of males, with 25 percent regular smokers.] In 1985, 33 percent of males were smokers, compared to 28 percent of women (Figure 4). Thus, substantial numbers of men compared to women have quit smoking. These differences in cigarette use rates between current and past cohorts of men and women will have a profound effect on mortality and morbidity patterns in the United States for years to come. Lung cancer deaths have already reported to have surpassed those for breast cancer in women. While the lung cancer death rate continues to rise for both men and women, among women, an increasing rate of increase is observed compared to a decreasing rate of increase in men. This changing pattern of lung cancer mortality reflects the declining percentage of smokers among men as well as their relatively higher quit rates, and lower rates of smoking initiation among contemporary age cohorts of men compared to women. 23

illustrates smoking's role in the causation of neoplastic diseases. A number of epidemiological studies published during the last two decades provides an abundance of data to analyze. In particular are the major prospective studies on smoking and health. These studies, conducted in the Untied States, Canada, England, Japan and Sweden represent some of the largest population based studies ever undertaken by medical science (Table 1). They involved enrolling healthy men and women into a study design and then following these individuals over time. Numerous factor about them were recorded including where they lived, their occupations, dietary habits, whether they used tobacco, access to health care, and many other factors. As a group, these eight studies in the United States, the U.S. Veterans Study and the American Cancer Society (ACS) 25-State Study contained cohorts of 290,000 and 1 million persons respectively. The Veterans Study continues to this day and this cohort has been followed prospectively for 26 years. These studies can provide significant insight into the association between smoking and lung cancer. Lung Cancer Lung cancer mortality rates are strongly influenced by the total dose or cigarette smoke received. If one smokes more cigarettes per day, inhales deeply, if they started smoking at an early age had has smoked for many years, the risk for lung cancer is increased dramatically. The most often used measure to gauge lung cancer mortality is the number of cigarettes consumed daily. In the ACS 25 State study, for example, among males smoking less than 1/2.pack per day their lung cancer rate was nearly 5 times greater than that of a nonsmoker. with each increase in the number of cigarettes consumed daily, a corresponding increase in lung cancer mortality is observed (Figure 5). For those smokers consuming two or more packs daily, their lung cancer mortality is between 15 and 25 times greater than that of the nonsmoker. Translated, this means between a 1,500 and 2,500 percent greater likelihood of developing and dying of lung cancer in heavy smokers compared to individuals who have never smoked. An inverse dose-response relationship exists between an early age of regular smoking initiation and lung cancer mortality. In the U.S. Veterans Study, those smokers who started smoking in their early teens had substantially higher lung cancer death rates that those who started in their late teens or twenties (Figure 6). 'Those who began smoking before age 15 experienced an 18-fold greater lung cancer mortality, compared to a slightly greater than 5-fold excess risk for those who initiated their behavior after age 25. 25 pn ~ O m M 3

The Health Consequences of Active Cigarette Smoking Cigarette smoking is now recognized as the Nations single largest cause of premature death and disability. Estimates of the number of premature deaths annually caused by cigarette smoking range from between 270,000 to 475,000. It can reasonably be concluded that between 300,000 and 350,000 preventable deaths can be attributed to smoking in this country. The number of persons suffering from chronic disabling diseases and conditions runs in the tens of millions. Every medical authority and organization who has objectively examined the evidence linking smoking to early death disability has reached a similar conclusion. The data base upon which a judgement can be made concerning smoking as a substantial health threat is staggering--over 50,000 citations from dozens of cultures are not in the published scientific literature. Cigarette smoking has probably been the most studied agent in the environment, but it has only been within the pst 25 years that medical and scientific opinion have become galvanized into doing something about its control. The need for control measures has become more evident with the accumulation or medical evidence linking not only ill effects to the smoker, but also possible chronic health effects on nonsmokers who live or work around smokers has emerged. Smoking and Cancer In the 1982 Surgeon Generals Report, the U.S. Public health Service identified a causal role between cigarette smoking and a variety of cancer sites. Cancers causally related to smoking include lung cancer, and cancers of the larynx, esophagus and oral cavity; smoking was also judged a contributing factor for the development of cancers of the bladder, kidney, and pancreas. More recently evidence has accumulated which suggest a causative role between cigarette smoking and cancer of the uterine cervix in women. Most•estimates published in the scientific literature indicate that nearly on-third of all cancer deaths that occur annually in the U.S. result from cigarette smoking. Thus, approximately 140,000 cancer deaths occurred last year because of smoking--the majority of these cancers are of the respiratory system. Lung cancer alone is responsible for fully one-quarter of all cancer mortality; were it not for lung cancer we would be experiencing a substantial decline in the cancer death rate in the United States. Approximately 85 to 90 percent of all lung cancer deaths are smoking related. The evidence linking smoking and excess cancer mortality is so strong that only the tobacco lobby continues to claim that no causative role has been established. An examination of the association between cigarette smoking and lung cancer graphically 24 }