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1 ! | I i i i 1 I I I APMIS SuppL 76: Fol. 10~," 9-47, 1997 Printed in Denmark. All rights reserved Copyright @ APMIS 1997 ISSN 0903-46.~X ISBN 87-16-15626-9 Tobacco smoking L. DREYER,~ J. E WINTHER,~ E. PUKKALA2 and A. ANDERSEN~ ~Institut~ of Cancer Epidemiology, Danish Cancer Society, 2Finnish Cancer R~gistry, ~Cancer R~gistry of Norway Dreyer, L., Winther, J. E, Pukkala, E. & Andersen, A. Tobacco smoking. APMIS Suppl. 76: Vol. 105: 9-47, 1997. Active smoking is causally associated with cancers of the lung, larynx, oral cavity, pharynx, oesoph- agus, pancreas, renal parenchyma, renal p~lvis and urinary bladder, and passive smoking appears to be causally associated with cancer of the lung. Information on smoking habits for the years 1965, 1975 and 1985 shows that more men than women in the Nordic countries were current smokers. The rates of women v~re stable over time and those of men were decreasing, approaching those of women. Lung cancer, in particular, is strongly associated with active smoking: by increasing the number of cigarettes smoked l~r da~ (lifelong) to 5, 10, 20 and 40 or more, the risk increases by five-, eight-, 16- and 30-fold, respectively, over that of people who have never smoked. Thus, with approximately 35% current smokers and 25% former smokers among Nordic men in 1985 and approximately 30% currant smokers and 15% former smokers among Nordic women in that year, by the year 2000 10,000 cases of lung cancer (6,500 in men and 3,500 in women) will be caused by active smoking; this is equivalent to 82% of all cases of lung cancer in thes~ populations. Another 6,000 cancers of other types (4,000 in men and 2,000 in women) are caused annually by active smoking, yielding a total of 16,000 n~w cases each yeax around the turn of the century. This implies that 14% (19°,4 in men and 9% in women) of all incident cancers in the Nordic countries around the year 2000 will b~ caused by active tobacco smoking. In comparison, passive smoking is a minor cause of lung cancer, responsible for approxi- mately 0.6% of all new cases (approximately 70 cases annually) in this area around the turn of the century. K~ words: Tobacco smoking; cancer incidence; prevention. L. Dreyer, Institute of Cancer Epidemiology, Danish Cancer Society. ACTIVE SMOKING Tobacco smoking is the major single cause of human cancer. It has b~en estimated that smok- ing of cigarettes was responsible for 30% of all cancer deaths in the United States in 1978 (1). In the Nordic countries, cigarette smoking has played a key role in the steady increase in cancer incidence observed in people of each sex over the past 30-40 years. In addition, regular to- bacco use is an important cause of non-malig- nant damage to the lung and cardiovascular sys- tem (2). Epidemiological studies initiated during the 1940s and 1950s in response to the dramatic in- crease in mortality from lung cancer observed in Europe and the United States established cigarette smoking as the major causal factor (3-- 10). Subsequently, thousands of scientific in- vestigations have confirmed this conclusion and have provided additional evidence that smoking is a cause of cancers at many other sites as well. In 1986, tobacco smoke was added to the list of agents found by the International Agency for Reseamh on Cancer (IARC) to be carcinogenic to humans (Group 1) (11). Tobacco smoke exerts its predominant card- nogenie effect on those tissues directly exposed, such as the bronchial lining of the lung; how- ever, organs distant from the smoke are also

DREYER et aL affected, since caminogens and pro-carcinogens are absorbed from the lungs into the blood- stream and circulated to all parts of the body. C~rtain carcinogens am found in particularly high concentrations in the urine of smokers (l 1,12). Although the oesophagus and stomach arc not directly exposed to inhaled cigarette smoke, its constituents condense on the mucous membrane of the mouth and pharynx and am swallowed; furthermore, mucus cleared from the lung reaches the oesophagus and stomach. The sites of cancer listed in Table 2.1 are causally linked to tobacco smoking. These are the types included in the overall assessment of the number of cancers avoidable if smoking were eliminated in the Nordic countries. More- over, cancers at the following sites are strongly suspected to be related to tobacco smoking: lip, liver, stomach, uterine cervix and bone marrow (leukaemia), and similar assessment have been made for these cancer types. Throughout the text and tables, however, the numbers of cancers thought to be avoidable have been kept separate from the numbers known to be avoidable. For all cancers causally linked to tobacco smoking, a dose-response relationship is seen, with decreasing risks observed after cessation of smoking. Overall, cancer rates arc modified by the following factors: type of tobacco used (amount of tar in cigarettes, presence or absence of a filter on cigarettes, cigars, cigarillos, pipe), the amount of tobacco smoked per day, the num- ber of years of smoking, the degree of inhalation, and, perhaps, individual susceptibility for cancer development (11, 13). Cohort and case-control studies conducted in the United States and the United Kingdom in the 1950s and 1960s generally showed two-to fourfold lower risk ratios for lung cancer among women than men for comparable levels of to- bacco consumption (13, 14). The difference was, however, partly a consequence of the fact that TABLE 2.1. Cancer types convincingly related to tobacco smoking P~spiratory Digestive Urinary s~ystvrn organs tract Larynx Oral cavity and l~nal paren- tongue chyma Lung Pharynx R~nal pelvis Oesophagus Urinary bladder Pancreas 10 women generally started smoking at a later age than men and more often smoked low-tar, filter- tipped cigarettes. As female smoking habits are approaching those of males, case-control and cohort studies conducted during the two last decades have generally shown little or no differ- ence in the risk for lung cancer by sex, for com- parable levels of tobacco consumption (13-20). Finally, it is important to be aware that to- bacco smoke may interact with other carcino- gens in the environment, e.g. ionizing radiation and asbestos, to produce particularly high rates of lung cancer or, with alcohol, high rates of cancers of the upper respiratory and digestive tract (21). When such synergism exists, it is dif- ficult to separate the effects of each carcinogenic exposure; in this wport, wc attempted to adjust for only the most important, best-described in- teractions. MATERIAL AND METHODS The proportions of cancers in the population that arc attributable to tobacco smoking - the population attributable ri~k percent (PAR°~) - w~re calculated on the basis of information on the sex-specific smok- ing habits in each Nordic country and estimates of the relative risk for each cancer site of relvvance to smoking (s¢~ also "Aims and Background"). Information on smoking Information on the smoking habits of men and women in the five Nordic countries was revi~w¢~l for the years 1965, 1975 and 1985 (Tables 2.2 and 2.3; 22-31). As the latency for the development of most solid tumours is about 15 y~ars, we assume that these cohorts are those most likely to contribute to the can- cot rates in 1980, 1990 and 2000. More detailed infor- mation on smoking habits can be obtained from the authors. Smokers of bbth cigarettes and other typ~s of to- bacco have bwn classified according to cigarette con- sumption, as use of cigarettes usually predominates and is associated with the highest relatiw risks for cancer. The term "pipe and cigar smokers only" re- fers to users of pip~s, cigars or cigarillos or combi- nations thereof. As reliable data on duration of smoking, degree of inhalation and age-specific smok- ing habits were not available for all countries, these variables w~re not included in the calculation of at- tributable risks. Detailed information on u,~ of smokeless tobacco (especially in fashion in Sweden today) was not available. The proportion of nonsmokers in each of the study I I I I I I I I I I I I I ,I I I I I

'.r1 l I ] TOBACCO SMOKING TABLE 2.2. Distribution of the adult male population of each of the five Nordic countries according to smoking habits in 1965, 1975 and 1985 Country Year Never Male smokers (%) smokers Ever Former Current Denmark 1965 13 87 1975 22 78 1985 39 61 Finland 1965 32 68 1975 37 63 1985 42 58 Iceland 1965 17 83 1975 20 80 1985 31 69 Norway 1965 22 78 1975 28 72 1985 34 66 Sweden 1965 26 74 1975 32 68 1985 43 57 Moderate" Heavyb 17 70 60 10 16 62 48 14 10 51 30~ 21d 18 50 18 32 32 31 11 20 24 34 15c 19d 19 64 42 22 25 55 37 18 27 42 31c lld 22 56 50~ 6d 27 45 38c 7a 28 38 30e 8d 23 51 42 9 28 40 22c 18r 30 27 11c 16r Data for 1965, 1975 and 1985 9r a close year • Current smokers of fewer than 15 cigarettes per day and smokers of pipe or cigars only b Current smokers of 15 eiga.rettes per day or more ¢ Current smokers of fewer than 20 cigarettes per day and smokers of pipe or cigars only a Current smokers of 20 cigarettes per day or more c Current smokers of 12 or fewer cigarettes per day and smokers of pipe or cigars only f Current smokers of more than 12 cigarettes per day populations was subdivided into "never smokers" and "former smokers". The,subgroup of former smokers is a heterogeneous group consisting of per- sons previously exposed to very different amounts of tobacco smoke, who quit smoking frbm a few months to several years before the survey. A comparison of Tables 2.2 and Table 2.3 shows that more men than women were "ever smokers" throughout the period. The proportion among men decreased consistently over time, however, due in par- tieular to decreases in the numbers of heavy smokers in Finland and of moderate smokers in Denmark, Norway and Sweden. The proportions of "ever smokers" among men in 1985 ranged from about 57% in Sweden to almost 70% in Iceland. In that year, Sweden and Finland had the lowest proportions of current male smokers (about 30%) and Denmark, Iceland and Norway the highest (about 40--50%). In all countries except Denmark, the proportions of for- mer smokers were relatively large (about 30%). The consistent increase over time in the proportion of "never smokers" indicates that fewer and fewer young men are taking up the smoking habit. Among women (Table 2.3), the proportion of"ever smokers" remained largely unchanged over the period 1965-85, the proportions in 1985 ranging from approximately 35% in Finland to 60% in Ice- land. The highest proportion of current smokers (43%) in 1985 was found for Danish women, ap- proaching that among men (51%). Relative risks for cancer Risk estimates for cancers known or suspected to be causally related to tobacco smoking were reviewed on the basis of the IARC monograph on tobacco smoking (11) and subsequent papers on this issue. Particular emphasis was paid to large cohort and case-control studies from the United Kingdom and the United States, and, when available, the Nordic countries, and the most representative relative risks for each cancer site were assigned to each of a num- ber of predefmed smoking categories. Study-specific relative risks associated with cigarette consumption (dose-response curves) are presented site by site be- low; summary estimates are shown in Table 2.4. The relative risks for "pipe and cigar smokers only" are rough estimates of the average risks associated with the speetlie smoking habit. Rough estimates of the relative risks of current smokers for cancer types only suspected to be related to tobacco smoking are shown in Table 2.5. All of the caleuiations are based on the assumption that the relative risks are equal for male and female smokers of equal amounts of tobacco. 11

DREYER et a~ TABLE 2.3. Distribution of the adult female population of each of the five Nordic countries according to smoking habits in 1965, 1975 and 1985 Country Year Never Female smokers (%) smokers Ever Former Current Moderatea Heavyb Denmark 1965 50 50 8 42 37 5 1975 41 59 12 47 37 10 1985 51 49 6 43 28¢ 15a Finland 1965 67 33 10 23 17 6 1975 71 29 13 16 9 7 1985 67 33 15 18 14c 4d Iceland 1965 42 58 13 45 26 19 1975 40 60 20 40 22 18 1985 41 59 22 37 32c 5a Norway 1965 63 37 14 23 22c 1a 1975 59 41 9 32 29c 3d 1985 50 50 18 32 27c 5d Sweden 1965 57 43 20 23 21 2 1975 49 51 17 34 18c 16f 1985 54 46 20 26 14~ 12r Data for 1965, 1975 and 1985 or a close year I| l ! II 1 Current smokers of fewer than 15 cigarettes per day and smokers of pipe or cigars only Current smokers of 15 cigarettes per day or more Current smokers of fewer than 20 cigarettes per day and smokers of pipe or cigars only Current smokers of 20 cigarettes per day or more Current smokers of 12 or fewer cigarettes per day and smokers of pipe or cigars only Current smokers of more than 12 cigarettes per day TABLE 2.4. Summary estimates of the relative risks for cancers known to be causally related to tobacco smoking, by smoking status and number of cigarettes smoked per day Site of cancer Never Former Current smokers smokers smokers No. of cigarettes smoked per day Pipe and cigar 1-9 10-19 20-39 >40 sm°kersa Lung 1.0 5.0 4.6 11.5 22.4 30.0 7.0 ! i 1 ! Larynx 1.0 2.5 2.5 5.4 9.9 13.0 3.5 Oesophagus 1.0 2.0 1.8 3.4 5.9 7.7 3.0 Pharynx 1.0 2.0 1.6 2.9 4.9 6.3 3.5 Mouth and tongue 1.0 2.0 1.6 2.9 4.9 6.3 3.5 Pancreas 1.0 1.0 1.2 1.6 2.1 2.5 1.0 Lower urinary tractb 1.0 1.5 1.5 2.5 4.0 5.0 1.5 Renal parenehyma 1.0 1.0 1.2 1.5 1.9 2.2 1.0 Comprises smokers of pipes, cigars and cigarillos only Includes cancers of the urinary bladder and renal pelvis RESULTS Lung cancer (ICD-7: 162) Lung cancer is a major global health problem and is de facto the commonest malignancy, having surpassed stomach cancer in the early 1980s (32). Lung cancer is particularly prevalent in industrialized countries; in Europe, it ae- 12 counts for 29% of all cancer deaths among men and 8% among women (33). Large variations are seen across country borders, between the two sexes and with age. In the Nordic countries combined, lung cancer is the second most fre- quent cancer in men, after cancer of the pros- tare, and the third most frequent cancer in women, only exceeded by breast cancer and co- I ! I

| ] ] ! i I i i i I I 1 TOBACCO SMOKING TABLE 2.5. Estimated relative risks for cancers at sites suspected to be related to tobacco smoking Cancer site Non-smokersI Current smokers Lip 1.0 2.0 Liver 1.0 1.5 Stomach 1.0 1.5 Leukaemia 1.0 1.3 Uterine cervix 1.0 2.0 a Never and former smokers lorectal cancer (34). In these countries nearly 10,000 new eases occur annually, approximately 7000 in men and 3000 in women (34--44). Relationship with tobacco consumption The predominant risk factor for lung cancer is cigarette smoking, but industrial exposures and radiation also play important roles (13). The combined results of the most important co- hort studies (Fig. 2.1; 2,8,17,45-52) give a risk for lung cancer that rises linearly, with an ap- proximate excess relative risk of 0.73 per ciga- rette smoked per day. Accordingly, by increasing the number of cigarettes smoked per day to 5, 10, 20 and 40 or more, the risk increases 5.0-, 8.0-, I6- and 30-fold, respectively, over that of "never-smokers". The risk for lung cancer is highest among cigarette smokers, but is also sig- nificantly increased among.smokers of pipes and cigars (Table 2.4; l l,13J. Former smokers have been allocated an average relative risk for lung cancer of 5 frab.le 2.4; 11). Tables 2.6 (men) and 2.7 (women) show the numbers of cases of lung cancer notified to each of the five Nordic cancer registries during 1980 and 1990 and the numbers estimated to occur in year 2000. The tables also give the corresponding crude incidence rates and the calculated pro- portions of cases caused by tobacco smoking (PAR%). While Finnish men had the highest numbers in 1980, with a crude incidence rate of 86 per 100 000 male inhabitants, Danish men took over this position in the next few decades, and the rate expected in 2000 is dose to 100 new eases per year per 100 000 inhabitants. The rate among Swedish men is about half of that seen in Danish men. The etude incidence rates of lung cancer among women (Table 2.7) are usually less than half those seen in the respective male popu- lations, but are dearly increasing over time. Large variations are seen between countries, however, women in Iceland and Denmark having the highest rates throughout the period. The pro- portion of lung cancers due to tobacco smoking among men in the Nordic countries in 1980 was 86%, and this percentage was unchanged in the estimate for 2000. Thus, 5,500-6,000 of the cases of lung cancer diagnosed annually among Nord- ic men in late 1970s and 1980s were due to smok- ing. In the year 2000, the number will be about 6,800 annually (Table 2.6). The corresponding PAR% were and will be somewhat lower in women (Table 2.7). The pro- portion of lung cancers caused by tobacco smoking was 72% around 1980 and 78% in 1990; around 2000, the proportion of lung can- cer among women due to tobacco smoking is expected to be 79%. These estimates are equiva- lent to about 1,300, 2,200 and 3,500 cases of lung cancer annually, respectively. Laryngeal cancer (ICD-7: 161) Laryngeal cancer predominates among men, with an estimated worldwide male:female inci- dence ratio of 7:1 (32). High incidences are re- ported from southern Brazil, Italy, France and Spain (32), while the rates in the Nordic coun- tries are much lower (34-44): in the combined Nordic populations of about 22.5 million in- habitants, about 600 eases were seen among men in 1990, and fewer than 100 among women. Relationship with tobacco smoking Tobacco smoking and alcohol drinking are important risk factors for laryngeal cancer, par- tieularly when combined (53-55); occupational hazards, including exposure to asbestos, may also be of some importance (32). Fig. 2.2 shows the dose-response relationships between ciga- rette smoking and laryngeal cancer, observed in a number of studies of relevance to the Nordic countries (53-64). As alcohol is also a strong risk factor, only studies in which adjustment was made for the effect of alcohol are included. Most of the studies reported an increase in the relative risk for laryngeal cancer that is approxi- mately proportional to the number of cigarettes smoked per day. In general, by increasing the number of cigarettes smoked per day to 5, 10, 20 and 40 or more, the risk for laryngeal cancer increases 2.5-fold, 4.0-, 7.0- and 13-fold, respec- tively, over that of "never-smokers", which corresponds to an excess relative risk of 0.30 per cigarette smoked per day. 13

DREYER ~t ~/, Relative risk 40 30 10 O; 5 10 15 20 25 30:35 No. of cigarettes/day 40 The overall relative risk for laryngeal cancer among smokers of pipes and cigars only is about 3.5 (53, 59, 62, 65), and the correspond- ing risk of the combined group of former smokers is about 2.5 (Table 2.4; 58, 59, 61, 62). Tables 2.8 (men) and 2.9 (women) give the key figures for laryngeal cancer in the Nordic popu- lations. A slightly increasing trend in the crude incidence rates for both men and women is seen over time, Danish men having the highest esti- mated rate of dose to 10 per 100 000 in year 2000. About 70% of the cases of laryngeal can- car in men and 60% in women that occur today and are foreseen to be diagnosed around the turn of the century in the Nordic counties, are caused by tobacco smoking, implying tobacco- 14 Fig. 2.1. Cohort studies: cigarette smoking and lung "°- Carstensen et al (45) " -I- Doll at al (2) ~."" Engholm et al (46) "~" Garlinkel et al (17) "~" Hammond et al (8) "~" Hammond et al (47) "~ Hakulinen at al (48) -e- Hakullnen et al (48) "~" Losslng et al (49) "~" Lund et al (50) "*" McLsughlin at al (51) • 4- Weir et sl (52) "~" Our estimate related PAR% that are almost as high as those for lung cancer. The findings indicate that around the year 2000, about 500 cases of laryngeal cancer will occur annually among Nordic men and 70 among Nordic wgmen, due to tobacco smoking. Oesophageal cancer (ICD-7: 150) Oesophageal cancer is characterized by an ex- treme diversity of rates throughout the world; there are usually more eases among men than women (32). Oesophageal cancer is rare in the Nordic countries in comparison with other parts of the world, such as Asia (34-44). In 1990, about 700 new cases among men and 300 I I

TOBACCO SMOKING a 1 ! ! n i TABLE 2.6. Proportions and numbers 1980, 1990 of cases of lung cancer avoidable among men in the Nordic and 2000 if tobacco smokin~ were eliminated countries in Country and year Annual no. Incidence PAR%• Avoidable of new cases per 100,000 number Nordic countries, 1980 6906 62.2 86 5925 Denmark 2130 84.2 86 1830 Finland 1983 85.8 89 1765 Iceland .42 36.5 87 35 Norway 962 47.5 85 815 Sweden 1789 43.4 83 1480 Nordic countries, 1990 6679 58.6 84 5635 Denmark 2018 79.7 84 1705 Finland 1629 67.5 86 1395 Iceland 61 47.7 86 50 Norway 1159 55.3 84 980 Sweden 1812 42.9 83 1505 Nordic countries, 2000 8102 68.6 84 6815 Denmark 2520 97.4 85 2150 Finland 1879 76.0 86 1620 Iceland 91 64.7 86 80 Norway 1313 59.9 84 1105 Sweden - 2299 52.1 81 1860 I I I I i I Population attributable risk percent TABLE 2.7. Proportions and numbers of eases of lung cancer avoidable among women in the Nordic countries in 1980, 1990 and 2000 if tobacco smokinf~ were eliminated Country and year Annual no. Incidence PAR.%" Avoidable of new eases per 100,000 number Nordic countries, 1980 1857 16.2 72 1330 Denmark 708 27.3 77 545 Finland • 299 12.1 71 210 Iceland 32 28.3 83 25 Norway 235 11.4 67 155 Sweden 583 13.9 68 395 Nordic countries, 1990 2826 24.0 78 2200 Denmark 1101 42.2 80 880 Finland 380 14.9 71 270 Iceland 38 29.9 83 30 Norway 458 21.4 75 345 Sweden 849 19.6 79 675 Nordic countries, 2000 4437 36.4 79 3490 Denmark 1800 67.6 82 1475 Finland 532 20.3 71 380 Iceland 75 53.8 83 65 Norway 624 27.9 79 495 Sweden 1406 31.1 76 1075 ! I • Population attributable risk percent among women were registered in the Nordic countries. Relationship with tobacco smoking Tobacco smoking and alcohol consumption are the major risk factors for cancer at this site in both men and women, especially when prac- tised in combination (21). In a number of studies in which alcohol consumption was ad- justed for, the magnitude of the increased risk for oesophageal cancer, appeared to be directly proportional to the number of cigarettes 15

DREYER ~ .L 4O 35 30 25 20 15 Relative risk Fig. 2.2. Case-control studies: cigarette smoking and la- ryngeal cancer, ad- justed for alcohol consumption. 5 0L 5 10 15 20 25 30 35 No. of cigarettes/day 4O smoked per day (54, 59, 66-73). Fig. 2.3 shows the dose-response relationships observed in rel- evant studies, with an excess relative risk of about 0.17 per cigarette smoked per day. Ac- cordingly, by increasing the number of cigarettes smoked daily to 5, 10, 20 and 40 or more, the risk increases by 1.8-, 2.%, 4.4- and 7.7- fold, respectively, over that of "never-smokers". Smoking of pipes and cigars only appears to increase the relative risk for oesophageal cancer to approximately 3 (Table 2.4; l l, 66, 67, 73, 74). Former smokers have an excess risk be- tween that of current smokers and "never smokers" (59, 66, 69, 70), estimated to be in the order of 2 (Table 2.4). 16 Tables 2.10 (men) and 2.11 (women) show that the crude rates of oesophageal cancer in the Nordic countries are almost unchanged between 1980 and 2000, with annual incidence rates of about 6 cases per 100,000 for men and 3 per 100,000 for women, respectively. Danish men and Finnish and Icelandic women have the highest rates. About 60% of the cases in men and 40% in women are attributable to smoking habits, corresponding to nearly 500 cases in the Nordic countries per year. Pharyngeal cancer (ICD-7: 14.5-148) Pharyngeal cancer is a relatively rare cancer in the Nordic countries (32), approximately 350 C) I I I ! I I I I I I I I I I I I I I

TOBACCO SMOKINO I I I I I TABLE 2.8. Proportions and numbers of eases of laryngeal cancer avoidable among men in the Nordic countries in 1980, 1990 and 2000 ~ tobacco smoking were eliminated Country and year Annual no. InCidence PAR%• Avoidable of new cases per' I00,000 number Nordic countries, 1980 590 5.3 71 420 Denmark 207 8.2 72 150 Finland 130 5.6 77 100 Iceland 6 5.2 74 4 Norway 85 4.2 70 60 Sweden 162 3.9 66 105 Nordic countries, 1990 591 5.2 69 405 Denmark 211 8.3 69 145 Finland 106 4.4 71 75 Iceland 6 4.7 71 4 Norway 108 5.1 69 75 Sweden 160 3.8 67 105 Nordic countries, 2000 720 6.1 68 490 Denmark 254 9.8 71 180 Finland 106 4.3 72 75 Iceland 6 4.3 72 4 Norway 142 6.5 69 95 Sweden ° 212 4.8 63 135 I I I I I I ! • Population attributable risk percent TABLE 2.9. Proportions and numbers of cases of laryngeal cancer avoidable among women in the tries in 1980, 1990 and 2000 ~ tobacco smoking were eliminated Country and year Annual no. Incidence PAR%• of new cases per I00,000 Nordic court- Avoidable number Nordic countries, 1980 74 0.6 52 35 Denmark 28 1.1 58 15 Finland • 8 0.3 50 4 Iceland 2 1.8 67 1 Norway 14 0.7 45 5 Sweden 22 0.5 46 10 Nordic countries, 1990 88 0.7 60 55 Denmark 48 1.8 62 30 Finland 8 0.3 50 4 Iceland 0 0.0 - - Norway 9 0.4 56 5 Sweden 23 0.5 61 15 Nordic countries, 2000 104 0.9 62 65 Denmark 68 2.6 65 45 Finland 8 0.3 50 4 Iceland 0 0.0 - - Norway 4 0.2 61 2 Sweden 24 0.5 56 15 .i ! 1 • Population attributable risk percent eases having been registered in 1990 in men and 125 in women (34-44). Relationship with tobacco smoking Like other cancers of the upper aerodigestive tract, pharyngeal cancer is associated with both tobacco smoking and alcohol drinking, and the combination of the two habits increases the risk further (I 1, 75). Few studies have addressed the risk for pharyngeal cancer associated with reg- ular cigarette smoking. The main results from the available studies are summarized in Fig. 2.4 17

DREYER et al. Relative risk 40 ,.r----~ ~ 0L 0 10 20 :30 40 No. of cigarettes/day (55-57, 59, 75, 76), which shows marked vari- ation in the magnitude of the reported risks, after adjustment for alcohol drinking. The risk for pharyngeal cancer rises with the number of cigarettes smoked per day with an excess rela- tive risk of approximately 0.13 per cigarette smoked. Thus, by increasing the number of cigarettes smoked daily to 5, 10, 20 and 40 or more, the risk increases by 1.7-, 2.3-, 3.7- and 6.3-fold, respectively, over that of "never- smokers". Smokers of pipes and cigars only seemed to have approximately the same risk as smokers of cigarettes (11), with an estimated av- erage of 3.5 (Table 2.4). A relative risk of 2.0 was allocated to the group of former smokers. Tables 2.12 (men) and 2.13 (women) give the 18 I Fig. 2.3. Case-control i studies: cigarette smok- ing and oesophagcal cancer, adjusted for al- I cohol consumption. ! ~ ~m ,t=l (S41 I I "{" Brown it al (66) "~" Fr~lI~hl it a! ($9) I "J" Need it al (69) ~" Tuyn= ~t a1171 ) "~ Tuy~ it =1 (7=) • ~" oiff il||mltel ! I key figures for pharyngeal cancer. Over the study I period, the crude rate increases in men but not in women. The rates are particularly high for [] Danish and Swedish men and Danish women. The calculated PAR% for laryngeal cancer re- lated to tobacco smoking is about 50% in men [] and 40% in women, corresponding to annual | expected numbers of 250 eases among men and 50 among women in the Nordic countries around the year 2000. • Cancers of the oral cavity and tongue (ICD-7; I 141 and 143-144) Cancers of the oral cavity and tongue are also rare in the Nordic countries, with approximate- I II I