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C" INTRQDiJ'CDION : Overview--The Health Consequences of Shiokin;g,

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CVER'VI'EW- HF.ALTH' CONSEOUENCES OF' SMOKING Tihe statement, "Warning: The Surgeon General Has Determined That C'igarette Smoking, Is Dangerous to Your Healthi,"" has been required by law on cigarette packaging since 1970 as a part of the Public Health Cig- arette Smoking Act of 1969. This Act was a response by the U'.S. Congress to the scientific information on the health consequences of cigarette smoking,suammar3!zed in reports then available (the Surgeon General's Report of 1964 and' thie subsequent' 1967, 1968, and 1969' PFS' Health Consequences of Smoking). This Act was plassedibecause a series of important questions,concernd'.ngcigarette smoking, andihealthhad beeni answered. The following discussion summarizes the basic questions, the methodology used to determine the answers, and the answers themselves. The initial question tobeanswe~red' concernin&the health consequences~ of smoking was "Are there any harmful health effects of smoking cigarettes?"' The answer to this question was provided in two ways. First,, it was demonstrated that some diseases occurred more frequently in smokers than in nonsmokers. Second, a causal relationship was established between smoking and' these diseases. A reasonable place to begj:n to look at the health consequences of' cigarette smoking was in thie area of overall death rates. If cigarette smoking,contributed substantially to the development of any major disease, th~is, would be reflected in a higher overall death,ratefor smokers:. Several large prospective studies have clearly shown that cigarette smokers have higher overall deathiratesth:aninonsmokers ofthe~ same ageandisex., Demonstrating,this association, however, was not enough to establish, the causal nature of'the relationship between smoking ancT excess deathh rates. The decision whether or not an association is causal is not merely a statement of statistical probability. Determining that the association between smoking and excess death rates is causal was ajudigement made by DHEW after a number of' criteria had' been met, no one of which by itself was sufficient to make this judgement. These criteria include: a. The consistency of the association.. b. The strength of the association. c. The specifici'ty of the association. d'. The temporal relationship of the association. e. The coherence of the association. 3

The association between cigarette smoking,and excess death rates has consistently been demonstrated in &large number of studies performed during the last 3©'years. The few studies not showing this relationship: had serious defect&in their design or analysis which limite&the interpre- tation of' their results. The strength of the association has~been firmly established by repeatedly showing that cigarette smoker&have one and a half to two and a half times the overall death,rates of nonsmokers. The specificity of the association was d!emonstrated by establishing that substantial excess overall death rate&occurred in:populations of smokers grouped by age, sex, race, socioeconomic class,; occupation, place of residence, and' many other variables. The temporal reLationshdipof the association between,cigarette smoking and overall death rates wasclearliy shown by the marked decrease in excess death rates that occurs after stopping; smoking. The coherence ofthe:ass,ociation wasestabl'ished'byshowing that aa dose-response relationship persisted' when dosage was.measured'by number of cigarettes smoked per day, duration of smoking, age at initiationlof smoking,,, depthof' inhalati'oni, or pack years ofsmoking., This relationship was alsed'emonstrated in prospective as: well as retrospective studie&. Thus, the extensive evidence concerning the health consequences of' smoking gathered by many researchers and analyzed'for consistency, - strength,, specifici't.,,temporal relationship,andcoherencehasclearl'yestablished cfigarette smoking, as the cause of'the excess mortality among, cigarette smokers. The establishment of, smoking as the cause of excess mortality broughtt up the additional question: "'How are the health consequences of smoking,, expressed'as individual disease processes?" The most important specific health consequence of cigarette smoking in; terms of the number of people:affected'is the development of premature coronaryh~eart d!isease(CHIa). Retrospecti've!studiiesestablished that cigarette~smokers, have agreaterrisk, of death due to:. CFIDand havs,ahigher prevalence of CHD~ thaninpnsmokers. Prospective studie&confirmedd that cigarette smokers have higher death rates from CEIDd and established that they have ah3gher incidence of'CEID than nonsmokers. Long-term folliowup of healthy populations~has confirmed that a cigarette:smoker is more likely to have a myocardial infarction and to die from CEID than a nonsmoker. Cigarette smoking has been shown to be one of the:maj',or independent CHDirisk factors and to act synergistically with the other majlor alterabl'e CHD risk factors (high blood pressure and'elevated!serum cholesteLol). Autopsy studies have shown that persons whiolsmoked.cigarettes have more severe coronary: atherosclerosd!sthan persnnw who, did'not smoke. 4

C A second major health cons quence.of smoking is the development of cancer in smokers. Cigarette smoking was firmly established' as the major cause of lung cancer by several large retrospective and prospective studies. The risk of developing lung cancer was found' to be 10 times greater for cigarette smokers than for nonsmokers. The risk of developing,lung,cancer increases with the number of cigarettes smoked per day: and is greater in cigarette:smokers who report inhaling, who started smoking,at an early age,, or who have smoked for a~greater number of years. Smokers of filter cigarettes have been shown to have a]:ower risk of developing lung cancer than smokers of nonfilter cigarettes,, but the risk remaines well above that for nonsmokers. The risk of developing cancer of the larynx, pharynx, oral cavity, esophagus, and urinary bladder was also~found!to be significantly higher in cigarette smokers than in nonsmokers. Pipe and cigar smokers were found to have elevated risks for the development of cancer of the oral cavity, pharynx, larynx, and esophagus when compared to nonsmokers. Pipe and cigar smokers report that they inhale muchiless frequently than cigarette smokers. As a result their lungs receive much less smoke exposure than cigarette smokers''. This is felt to be the reason for the lower incidence of cancer of' the lung for pipe and cigar smokers compared to cigarer,te smokers. FTomen have had'far lower rates of lung cancer than men. This has been attributed to women's tendency to smoke fewer cigarette per day, the fact that fewer women than menismoke, and the fact that women smokers generally select filter and low tar and nicotine cigarettes. However, the percentage of women smokers in the Hnited States has increased dramatically in the last 30 years, and since 1'9'S5 the death rates from lung cancer in women have.increased proportionately more rapidlyttian the rates~for men, reflecting this increased proportion of women smokers. The tar from cigarette smoke has been found'to ind'uce malignant changes in the skin and respiratory tract of'experimental animals,; and a number of specific chemical compound's contained in cigarette smoke were established as potent carcinogens or co-carcinogens. Malignant changes including carcinoma in situ were found in the larynx and in the sputum exfo!liative cytology of experimental animals exposed to ci'garette smoke. Nonmalignant respiratory: disease is a third area of smoking-fnd'uced morbidity and mortality. Cigarette smokers have.been shown to have more frequent minor respiratory infections, miss more dayrs from work due to respiratory illness,, and report symptoms of cough and sputum production more frequently than nonsmokers. Retrospective an&prospective studies with long-term fo]:lowup have found that cigarette!smoking is the primary cause of chronic bronchitis and emphysema in the United States. Cigarette smokers have also been found to be more likely to~ have abnormalities of their pulmonary function tests and1have higtier death rates• from respiratory 5

diseases than nonsmokers. Data from autopsy studies have shown that cigarette smokers were more likely to have the macroscopic ctianges of'. emphysema, and that these changes are closely related to the number of. cigarettes smoked'per day. Mucous cell hyperplasia has been found more often in cigarette smokers. Cigarette smoke also inhibits the ciliary motion responsible for cleansing, the respiratory tract. An add'itional area of hea];th concern has been the effect of cigarette smoking during pregnancy. Mothers who smoke cigarettes during, the last two trimesters of their pregnancy have been found to have bablies& with a lower average birth weight thaninonsmoking mothers. In addition cigarette smoking mothersh~ad alhigh~errisk of having astililborn child, and their infants had higher late fetal and neonatal death rates. There are some deta to show that these risks due to cigarette smoking,are evenn greater in women who have a high risk pregnancy for other reasons. These effects may occur because carbon monoxide passes freely across the placenta and'is readily bound by fetal hemoglobin, thereby decreasing thee oxygenicarrying capacity of fetal blood'. Having established' the health consequences of smoking, two additionall questions became important. They are, "'Canithe health consequences to the individual be averted by stopping smoking or by changing the cigarette?"and'"What are the overall public health consequences of cessation?"' The first question is the simpler of the two to answer. In the individ'ua1„ cessation of cigarette smoking resullts~iiv a:rapi&declineof the carb on monoxide level in the blood over the f i'rs t 12' hours. gymptoms of cough, sputum prod'uction, and shortness of breathiusually improve over the next few weeks. A woman who stops smoking by the fourth month of her pregnancy has no increased risk of stil~:lbirth or perinatal death in her infant rel~;ated!to smoking. The d'eterioration in pulmonary function tests that occurs inisome smokers becomes less rapid than that of'continuing,smokers. The death rates from ischemic heart d'isease, chronic bronchitis, and'emphysema also quickly become less thanithose of the continuing smoker. The risk of d'eveloping, cancer of' the lung, larynx, and oral cavity declines substantially in ttiefirst fewyears, after cessati'on and 10 to 15 years after stopping smoking approximates that of nonsmokers. A smoker who switches to filter cigarettes and' has smoked'ithem for 10 years or longer has a lower risk of developing,lung cancer than aismoker who continues to smoke nonfilter cigarettes. The risk to a filtered cigarette smoker, however, still remains well above that of a nonsmoker. The public heal'th benefits of'cessation are more difficult too determine than the effects of' cessation on the individual. Just as

C cause-specific death rates have reflected the effect of cigarette smo&ingg on certain diseases, they shouldialisoreflect any substantial beneEitsto be gained by cessation or reduction in cigarette smoking. Several factors combined to produce a reduction in per capita dosage of tobacco, exposure in the Unitedi States for the years 19661-19'70. FYrst, per capitaa consumption of cigarettes declined'from 4„287 cigarettes per person in 1966 to 3,985 in 19'70. Second, during this period there was a slow but significant decrease in the average tar and'ni'cotine content of' cigarettes as well as a decrease in the amount of tobacco contained in, the average cigarette. The decline in p r capita consumption d'uring those years occurred'in the'face of a substantial increase in the proportion of'women smokers and so reflected predominately a decrease iin cigarette consumption by men. Since 19,701, althoughithe per capita consumption of cigarettes has increased„ the average levels of tar and' nicotine have continued' to decline, making it more difficult to predict what has happened to per capita dosage.. Examination of cause-specifilc death rates for the period of this dieclining, per capita consumption (Tab1e 1)i reveals that there was a downturn in the male deathirate from: ischemic heart disease beginning,in 1966 which reversed the upward trend that had occurred over the previous two decades. This decline in the death rate from ischem2c heart disease has not occurred in women. The male deathirate from chronic bronchitis has also been declining since 1967, and'the male death rate for emphysema has declined since 1968 when it was first recorded as a separate category. Female death rates for these two diseases have not shown these trends. Despite the impressive coincidences of the decline in deathi rates among,maTes occurring, at the same time that there was a decline in per capitalcigarette consumpti'on,, it is impossible to be certain of the exact cause of the decline in th~e'deathrates- These d'iseases,areinfluenced by a variety of factors, in addition toicigarettesmok.ing, such as blood pressure and air pollution. Some of these factors have also been.subject to major control efforts which may have contributed to the decline in the death rates. In addition, there have been therapeutic advances in the treatment of these problems which may also tiave helped lower the death rates. A decline in male d'eath rates from lung cancer should also follow the decline in p~ercapi'taconsumption. This rate would not be,influenced asmuchs by chanlaes in other etiologic factors or changes in therapy because cigarette smoking causes from 85 to 90 percent of all lung cancer and there have been no major improvements in survival due to changes in, therapy. GJith lung cancer, 7

, ~ZlrY,.!" :,:,.. . •:~'.-.h t:, ..t~ ., ,... r .... Ischernic Heart Utsease ,: puronirBronchit9s P (410-413)2e«3 T r s (490,491)2 ; ~.'i,V ..P.-1 ~' i r1.ir ({,r.nAd TABLE 1 beatkrQtas for selected cauges, b}+ scx 146 3-1'9731'' Year 1963 1964 1965. 1966 1967 1968 1969 1970 1971 1972 1973' Y W;<=~ .« 4 S r, : Emphysema (492)2,4: 361.6 2209 i;.~.S.f4.3 1.6 Y' 354'.2 ~ 218.5 L§ } y' ltC ~;4•2 , 1 5 ;; E i xis cr 6 2221 . . -.1., 43 16 361.6 226.5 4.7 1.6 3'57.0 225 4 4.8 1 6 `. ` G ". t t 40017 , : 277.5 p) -0 4.7 - 16 ~392:0~j,273.6 0 .-f .~ ,34:4 1.4 zi.~ 272'0 , 387:2 , ; ~..• # fs` 4.3 14 . :; Y '`381.0 273.8 tl t'~. ~~._:..4'.0 1.4 .. 382.4 277.6 ' ` 4:2' 1.5 '378.5 276.01 . • 3:8' 1i.5' .{; 18.2 3:9 60.3 14.8 17:6' 61.3 _ 15 4 '.' . . r 43.0 -7~:5, 44.4 7:7ii 46.0 8.3 48.0 8.9 r: 20:9 3.7' 53.5 111, 1~ F119'•5' 16,' c` 54.7 , 111.8 r..\ U9L11 "3,7 S7A ., 126 s . . 18.3 3.8 ,. .. 57.8' 133 ~`"`'. 4 t Campil'edl frem Vitat Statistics of the United States, volumes Service, U.S, Department of Hlealth. Educatipn, for L963 iiA73 National Center for Health Staais6ics Public Health and Welfare IVUmbens after causes of death are category numbers from the Eighth, Revision of the internationall Classification of Diseases, used' in :J , Vital Statistics of the United States beginning iri 1968; prior to 1968 S h e t eventll udL Revision wasse 3The rates for 1963-11967 are for the category Arteriosclerotic Heart Disease inclluding,Coronary Disease (4'z0) and for 1968•1973, thee category Isahemic Heart Disease (410-413) to reflect a c1Ymificati h on c ange from the Seeth Eihh Ft ,vn togtevision. - 4Emphysema was recorded as: a separate category beginning,in 1968 with the Eighth Revision. ~ tt , r~rt^:,'.`( ~ ~....,~ . . :~.{. .. .- . . .4 Ij1 o)S.?~~•~1:..".i et4ibv, ~t1, Y.Ki. „ ? . .. "'+'.. ,. f j:...~/:..T F.. ('160:rll63) Z _ p E Yt' IuialSgnan t Neopllasms of ' iRt;spiratory System '' i ?r « . 33 8 s

C however, two, additional considerations must bekeot in mind. A d'eclinein death rates.Irom lung cancer would be expected to lag several years behind adecl!ine,.in peT capitaconsumption.In~ addition, thed'eclinein consumption and swi'tc'tu to;low tar and nicotine cigarettes occurred predominately in the Younger age %roups where death rates from lung cancer are low partly b'eca''.se of~ the long latent period, (about 2'0 years)' between onset of ex, posure to cigarette smoke and the development of lung cancer. For thesee reasons, it is necessary to look at lung cancer death rates by age group rather than total lung cancer death rates. The lung cancer rates by age groups for 1971 show that there may be aidecline inithe lung cancer rates for the younger males (under 4S), but the confidence limits on these trends at present remain wide enough to make it impossible toisay whether it is a real decline or merely a leveling, off. The national health statisticss broken down by age group are currently available only through 1971. The data by age group from a few more years will be necessary to determine accurately whether the lung cancer death rates are going down or leveling,off. The total death rates for all respiratory tract cancer are available through 1973; they showacontinuedlincrease, in boththemale and femaIedeatli rates reflecting,the fact that older age groups have both a higher incidence of respiratoryy tract cancers and have not had as large a change in smoking-behavior. A demonstration of a decline in male, age-specific death ratess for lung,cancer would add one more important piece of data to the already substantial evidence on the health consequences of smoking. 9

CHAPTER 1 CARDIOVASCULAR'DISEASES