TABLE 3.-Outline of prospective studies of smoking and overall mortality Doll Hill Dom Best Weir Cede&f Authors Pet0 Hammond Kahn Hirayama J&e Hammond Dunn Friberg Pike Roget Walker Horn Linden Hmbec (4-10) Brwlow (14,1&19) (If ,26,92,98) Lorkh (fZ,.zS-25) (l,N Gw U.&J93 (9 Males and Total population females California Probability British U.S. of Subjects Canadian White males in 29 health males in sample of doctors veterans in 2.5 the districts in pensionem various St&3 nine States Japan occupations Swedish population Population size wo@J l,CW@J 2woo =.%~ Females %W 6,~ 187,ooO 562,671 @w@J m 1.93 1.69 l.ss(>W 1.96 221 1W>16) 40+ 2.20 1.89 2.B 1.83 All smokerj 1.63 1.83 1.55 1.25 1.54 1.74 1.78 1.58 TABLE 5.-Mortality ratios for male cigarette-only smokers, by number of cigarettes smoked per day and age. U.S. veterans 1954 cohort, 16-year followup Number of Age cigarette3 per day 3b.34 3&u 45.54 5544 &74 Nonsmokers 1.00 1.00 1.00 1.00 1.00 less than 10 1.94 1.44 1.44 1.20 1.15 l&20 1.27 1.79 1.64 1.49 1.30 2139 1.76 2.23 2.10 1.67 1.42 40+ 2.33 2.72 2.13 1.&i 1.65 All smokers 1.52 1.95 1.33 1.53 1.32 SOURCE: Roget, E. (81.~8) significant mortality ratio that varies from 1.25 to 1.45. Smokers of more than two packs of cigarettes a day have an overall mortality ratio that varies from 1.33 to 2.23. Mortality at Different Ages Overall mortality ratios by amount smoked at different ages for several studies are presented in Tables 5 through 8. There is a decrease in the mortality ratio with each increase in age for each smoking category. Mortality ratios are consistently more than 2.00 for heavy smokers between the ages of 30 to 50. These ratios decrease gradually with age, but are still about 1.35 for men over 75 years of age. This decline does not imply a decrease in the effect of cigarette smoking on health. Overall mortality rates increase dramatically with age in both smokers and nonsmokers. If one uses another measure of mortality and looks at the difference. in death rates between smokers and nonsmokers as illustrated in Table 1, it can be seen that the difference in overall mortality rates increases with age even though the mortality ratio decreases. The decreasing mortality ratio with age is probably due to another factor that should be considered. The population of older males who smoke two packs of cigarettes per day is probably quite different than a younger group of two-pack-a-day smokers. Mortality by Duration of Smoking Overall mortality ratios increase with the duration of the smoking habit, Mortality ratios by number of years smoked from two studies are presented in Tables 9 and 10. The mortality ratios remain quite low, only slightly above the rates for nonsmokers for the first 5 to 15 Years of the smoking habit, and then increase more rapidly as the years 2-17 TABLE S.-Mortality ratios for male cigarette-only smokers, by number of cigarettes smoked per day and age. Males in 25 States Number of cigarettes per day Age 3544 4.554 5564 65-74 75-84 Nonsmoker 1.00 1.00 1.00 1.00 1.00 l-9 .I 1.34 1.53 1.50 1.36 l&19 1.36 2.26 1.92 1.65 1.55 20-39 1.91 2.41 205 1.71 1.26 40+ 259 276 226 1.81 o ? All smokers 1.32 2.20 1.36 1.53 1.35 SOURCE: Hammond. EC. (In. TABLE `I.-Mortality ratios for male cigarette-onl~ smokers, by number of cigarettes smoked per day and age. Canadian pensioners Number of Age cigarettes p"r day 30-34 3544 4554 55-64 674 75+ Nonsmokers 1.00 1.00 1.00 1.00 1.00 1.00 l-9 0.72 1.25 1.07 1.50 1.32 1.31 10-20 1.22 1.36 1.20 1.94 1.40 1.33 20+ 1.01 1.35 1.27 2.15 1.45 1.42 All smokers 0.90 1.63 1.21 1.39 1.45 1.31 SOURCE: Doll, R. (9) TABLE &-Mortality ratios for male cigarette-only smokers, by number of cigarettes smoked per day and age. Males in nine States Number of cigarettes per day Age 5&54 5549 w64 65-a Nonsmokers 1.00 1.00 1.00 1.00 l-9 1.43 1.15 1.46 1.37 1CKB 1.72 1.65 1.33 1.59 21-39 2.11 1.33 2.20 1.65 40+ 2.30 2.84 1.56 1.34 All smokers 1.35 1.69 1.34 1.55 SOURCE: Hammond, E.C. (PO). of smoking increase. Mortality ratios are as high as 1.66 for male cigarette smokers who have smoked for 35 or 40 years. 2-18 TABLE 9.-Age-adjusted mortality ratios for male cigarette-only smokers, by duration of smoking. Canadian veterans Duration of smoking in years Mortality ratio Under 5 1.05 5-14 1.30 lN?l 1.33 3039 1.53 40+ 1.66 All smokers 1.52 SOURCE: Best. E.W.R (I) TABLE lO.-Age-adjusted mortality ratios for male cigarette smokers who began smoking after the age of 20, by duration of smoking. U.S. veterans Duration of smoking Mortality in years ratio Under 15 1624 2534 35+ SOURCE: Kahn, H.A. (PS). 1.10 1.34 1.44 1.66 Mortality by Age Began Smoking Overall mortality ratios exhibit an inverse relationship with age of initiation of the smoking habit. Table 11 displays data from the U.S. Veterans Study. Cigarette-only smokers who began smoking after the age of 25 have a mortality ratio of i.32. For individuals who began smoking under the age of 15, the mortality ratio is 1.86. Data from the Japanese study are shown in Table 12. Again, a dose-response relationship is demonstrated but at a lower level than in the United States. When the Japanese data are broken down further "by age at start of study" and "age began smoking," as seen in Table 13, it is demonstrated that smokers who began smoking under the age of 15 have mortality ratios that are very similar to those in the United States data. Tables 14 and 15 show- overall mortality ratios by "age began smoking" and "age at beginning of study" for the U.S. veterans and U.S. males in 25 States. Overall mortality ratios by "age began smoking" and "number of cigarettes smoked per day" for the ACS Study of 25 States and the U.S. Veterans Study are presented in Tables 16 and 17. As expected, 2-19 TABLE Il.-Age-adjusted mortality ratios for male cigarette-only smokers, by age began smoking. U.S. veterans 1954 cohort Age began smoking in yea-3 Mortality ratio Nonsmokem 1.00 25+ 1.32 2iL24 1.51 15-19 1.64 Under 15 1.86 SOURCE: Roget. E. (91, SS). TABLE 12.-Age-adjusted mortality ratios for male cigarette-only smokers, by age began smoking. Japan Age began smoking Mortality in years ratio Nonsmokers 1.00 W+ 1.19 20-24 1.19 Under 20 1.27 SOURCE: Hirayama, T. (Z'.?). TABLE 13.-Age-adjusted mortality ratios for Japanese male cigarette smokers, by age began smoking and age at start of study Age began Age at start of study smoking in "ears 40 49 5&59 W-69 Nonsmokers 1.00 1.00 1.00 35+ 1.53 1.08 1.02 3&34 0.89 1.11 1.23 2529 0.91 1.17 1.19 m-24 0.82 1.16 1.19 15-19 0.92 1.31 1.29 Under 15 2.26 3.94 1.36 SOURCE: Hirayama. T. (Pe). overall mortality ratios increase the younger a person begins smoking and the greater the number of cigarettes smoked per day. Mortality by Inhalation of Cigarette Smoke Inhalation of tobacco smoke is an important dosage variable. Most of the excess mortality associated with cigarette smoking results from diseases that require inhalation of smoke well into the lungs in order to Z-20 TABLE 14.-Age-adjusted mortality ratios for male cigarette-only smokers, by age began smoking and age at start of studv. U.S. veterans 1954 cohort Age began Age at start of study smoking in years 30434 3544 45-M 5.544 &74 NonsmokeR 1.00 1.00 1.00 1.00 1.00 25+ o ? 1.48 1.67 1.36 1.20 20-24 1.41 1.87 1.72 1.56 1.39 15-19 1.44 2.00 2.11 1.70 1.45 Under 15 2.00 2.18 2.25 2.02 1.42 SOURCE: Ro& E. (SI. SS). TABLE 15.-Age-adjusted mortality ratios for male cigarette-only smokers, by age began smoking and age at start of study. Males in 25 States Age bw Age at start of study smoking in years 4554 5564 674 75-84 Nonsmokers 1.00 1.00 1.00 1.00 30+ 1.40 1.33 1.23 1.10 25-29 1.81 1.75 1.25 o ? ???? 2.13 1.73 1.52 1.27 15-19 2.49 211 1.34 1.53 Under 15 3.01 2.26 200 1.59 SOUFtCE: Hammond, E.G. (17) TABLE 16.-Age-adjusted mortality ratios for male cigarette-only smokers aged 55-64, by age began smoking and current number of cigarettes smoked per day. Males in 25 States Age began smoking in years Nonsmokers Current number of cigarettes per day 19 lo-19 as39 40+ 25+ 1.00 1.34 1.63 1.48 1.77 15-24 1.00 1.45 1.89 2.05 2.23 Under15 1.00 .I 2.15 2.19 2.53 ~URCE:Hammond, E.C.(I?). expose target organs directly or through absorption of toxic substances into the circulatory system. Ischemic heart disease, lung cancer, and chronic obstructive disease are not as likely to develop in individuals who do not inhale smoke. Techniques for quantitating inhalation have been developed using carboxyhemoglobin as an index of smoke inhalation, but these methods have not been applied to studies of overall mortality. Most studies asked the smoker to report subjectively 2-21 TABLE 17.-Age-adjusted mortality ratios for males smoking cigarettes only, by amount smoked and age began smoking. U.S. veterans 1954 cohort Age began Current number of cigarette3 smoking per day in years Nonsmokers l-20 21+ `B+ 1.00 1.36 1.59 Under 20 1.00 1.56 1.82 SOURCE: Roget, E. (31. J.?). on his own inhalation practices. Certainly, self-reporting of inhalation is subject to considerable variation, but it may not be as inaccurate as might be presumed. Available data show the expected dose-response relationship between inhalation of cigarette smoke and overall mortality. Table 18 demonstrates that with advancing age the percentage of moderate and deep inhalers drops and the percentage of none-to-slight inhalers increases. This is consistent with increased mortality for those who inhale. It also makes the interesting point that a smoker who survives to old age is different from the younger smoker. It is likely that the lower mortality ratios experienced by older smokers are partly a reflection of the fact that they smoke in a less hazardous fashion than do younger smokers. Older smokers are less likely to inhale than younger smokers. It is also likely that they take fewer puffs per cigarette and smoke fewer cigarettes per day. If they have been faithful to their brand of cigarettes, they are likely to be smoking an "older" brand. The brand is likely to be unfiltered and more typical of the cigarettes sold 30 to 40 years ago which contained twice the tar and nicotine of the average cigarettes sold today. Tables 19,20, and 21 show age-adjusted mortality ratios by degree of inhalation and number of cigarettes smoked per day and age at start of study for three of the large prospective studies. The overall mortality ratio is `2.80 for the moderate-to-deep inhaler who smokes 40 or more cigarettes per day. The overall mortality ratio is 2.53 for 45- to 54-year-old men who inhale deeply, but is 1.02 for noninhalers who are `75 to 84 years old. In the Canadian study, the highest mortality ratio was 2.11 for those 60 to 69 years old who reported inhaling cigarette smoke. Hammond reported a mortality ratio of 1.41 for noninhalers who are 45 to 54 years old (15). This suggests that cigarette smokers may underestimate the extent to which they inhale cigarette smoke. Mortality by Tar and Nicotine Content of Cigarettes Overall mortality increases with the tar and nicotine content of cigarette smoke. This relationship was recently examined by Ham mond, et al. (19). In this study, tar and nicotine levels (T/N) were defined as follows: "High" T/N, 25.8357 mg tar and 2.c2.7 mg 2-22 TABLE l&-Percent distribution of male cigarette smokers by * degree of inhalation of cigarette smoke and age. Males in 25 States Degree of inhalation 4&49 XL59 Age 6&69 70-79 i None 3.62 6.11 11.46 19.74 Slight 10.97 13.6-I 20.18 25.56 Moderate 57.94 56.31 51.10 40.82 D*P 27.65 23.91 17.25 13.83 Total 100.00 100.00 160.00 lOO.CQ SOURCE: Hammond. E.C. (19). TABLE lg.-Age-adjusted mortality ratios for male cigarette-only smokers, by degree of inhalation of cigarette smoke and current number of cigarettes per day. Subjects aged 45-54 at start of study. Males in 25 States NJ= Number of cigarettes pet day of inhalation l-9 lo-19 m-39 40+ None-slight 1.70 1.99 234 233 Moderatedeep 1.95 2.35 242 2.30 %XJRCE: Hammond. E.C. (17) TABLE 20.-Age-adjusted mortality ratios for male cigarette-only smokers, by degree of inhalation of cigarette smoke and age at start of study. Males in 25 States ~~ of inhalation Age at start of study 4544 5544 6.574 7584 None 1.41 1.43 1.32 1.02 Slight 1.67 1.71 1.31 1.19 werate 206 1.68 15.3 1.10 D=P 2.58 1.88 1.68 o ? SOURCE: Hammond, EC. (17) nicotine; "Medium" T/N, 17.6-25.7 mg tar and 1.21.9 mg nicotine; `%oW" T/N, less than 17.6 mg tar and less than 1.2 mg nicotine. Table 22 shows the overall mortality ratios of male and female smokers by thes tar and nicotine levels. In this instance, the mortality ratio of the "high" T/N smokers is represented as 1.00 so as to illustrate the reduction in overall mortality that occurs with lower T/N cigarettes. There is a small but statistically significant (P. less than 0.0005) reduction in the risk of dying with the use of lower T/N cigarettes. The rnortaIity ratio was reduced to 0.91 for the "medium" T/N smokers and 2-23 TABLE 21.-Age-adjusted mortality ratios for male cigarette-only smokers, by degree of inhalation of cigarette smoke and age at start of study. Canadian veterans Degree of inhalation 3cL-39 Age at start of study 4&49 5049 60-69 (D Nonsmokers 1.00 1.00 1.00 1.00 Do not inhale 0.61 0.61 1.10 1.78 Inhale smoke 1.29 12 1.58 211 SOURCE: Best, E.W.R. (I). TABLE 22.-Adjusted mortality ratios for males and females, by tar and nicotine content of cigarettes usually smoked Mortality ratios sex "High" "Medium" "Low" T/N T/N T/N Males 1.00 0.94 085 Females 1.00 0.88 0.33 Total l.M) 0.91 O.&p SOURCE: Hammond, EC. (19). TABLE 23.-Adjusted mortality ratios for males and females smoking low T/N cigarettes and subjects who never smoked regularly sex 3lortality ratios "h,$' T/N Nonsmokers Males 1.00 0.61 Females 1.00 0.14 Total l.GO 0.66 SOURCE: Hammond. E.C. (19). was further reduced to 0.84 for the "low" T/N smokers. The mortality ratios are lower for females than for males. In a separate analysis, a comparison was also made between the mortality ratios of "low" T/N smokers and nonsmokers. These data are presented in Table 23. The mortality ratio of the "low" T/N group was designated as 1.00. Nonsmokers have overall mortality ratios that are about half those of "low" T/N smokers. The combined data from these two tables are shown in Table ?A. Here, mortality ratios are calculated using nonsmokers as the 2-24 TABLE 24.-Overall mortality ratios of cigarette smokers compared to nonsmokers, by sex and by tar and nicotine content of cigarettes usually smoked Males Females Sex Non- "Low" "Medium" "High" smokers T/N T/N T/N 1.00 1.66 1.35 1.96 1.00 1.37 1.45 1.65 Total SOURCE: Hammond, E.C. (19). 1.00 1.52 1.64 1.80 reference. Combining these data from two separate analyses that are not exactly comparable results in figures that are only approximate. Hammond (19) also compared death rates of smokers of relatively few (1-19) "high" T/N cigarettes with those of smokers who smoked relatively large numbers (B-39) of "low" T/N cigarettes. The death rates of these two groups were very similar and the difference between them was not statistically significant. MothMy and Female Cigarette Smokers It is important that attention be called specifically to the mortality that females experience as a result of cigarette smoking. There has been an increase in smoking among teenage girls over the past 10 years. At present, the percentages of teenage boys smoking and teenage girls smoking are nearly identical. For some ages, there are more teenage girl smokers than boy smokers. Over the past 10 years, there has been a gradual reduction in the percentage of the adult population that is smoking. Men have quit in greater numbers than women. There has been only a modest drop in the percentage of women who are smoking. In Canada and several European countries, smoking is decreasing among men but increasing among women. In the United States, physicians, dentists, and pharmacists have been the most successful professional groups in giving up smoking, but in the past several years there has been an increase in smoking among nurses. Several suggestions have been made as to why women do not quit smoking. It may be that women do not generally perceive smoking as a threat to their health. Lung cancer, heart attacks, and emphysema are diseases that affect men more commonly than women. Women may feel that they are in a low-risk group. Women took up smoking later than men, generally smoked filter cigarettes, and smoked fewer cigarettes per day than men. Lower overall death rates for women smokers are due to lower exposure to cigarette smoke. Cigarette smoking for some women may be symbolic of equality with men. It is known that the smoking habits of women employed 2-25 TABLE 25.-Age-adjusted mortality ratios of female cigarette smokers, by number of cigarettes smoked per day and age. 25-State Study Number of Age cigarettes per day 544 4.554 5M4 6L74 75-84 NonsmokeR l-9 lo-19 20-a SOURCE: Hammond. EC. (17). 1.00 1.00 1.00 1.00 1.00 0.90 0.95 0.99 1.03 1.07 0.97 1.22 1.31 1.18 1.21 1.35 1.54 1.46 151 o ? outside the home match the smoking habits of men in various occupations where men and women hold equal positions. Women with the lowest rate of smoking are housewives who at present have few male counterparts with whom to identify. Recent surveys have shown that women are also concerned about weight gain that may accompany quitting smoking. Any significant weight gain on quitting represents an increased intake of food, but if one watches the diet on smoking cessation, weight gain can be avoided; in fact, weight loss can be achieved. In recent years, a few investigators have studied the relationships between cigarette smoking and the development of lung cancer and coronary heart disease in women. Death rates for these diseases are similar in women and men who have similar levels of exposure to cigarette smoke; the associations are outlined in later chapters dealing with specific diseases. Overall mortality rates for women available at present are from studies initiated 10 to 20 years ago, and thus reflect the differences in accumulated exposure that were operative at that time. Overall mortality in women varies in the same direction and in a similar degree as men for the dosage variables commonly measured. Overall mortality for women increases with the number of cigarettes smoked per day (Tables 25,26, and 2'7). Table 26 shows that the overall mortality ratio is 2.19 for females smoking more than two packs a day and inhaling moderately to deeply. Table 27 demonstrates that the mortality ratio is 1.85 for females smoking more than two packs per day who began smoking between the ages of 15 and 24. Mortality ratios by "inhalation" and "age at start of study" are shown in Table 28. Noninhaling smokers have mortality ratios that are similar to nonsmokers. Females with an average age of 50 who inhale smoke deeply have a mortality ratio of 1.78. Mortality and Ex-Smokers There is a general recognition among smokers and nonsmokers alike that cigarette smoking is a major cause of disease and death in the 2-26 TABLE 26.-Age-adjusted mortality ratios of female cigarette smokers, by number of cigarettes smoked per day and degree of inhalation. Subjects aged 4554 at start of study. 25-State Study Number of cigarettes per day Degree of inhalation of smoke None-Slight Moderate-Deep l-9 0.85 1.04 l&19 1.27 1.17 a-39 1.41 1.58 40+ .* 219 SOURCE: Hammond, EC. (I?`) TABLE 27.-Age-adjusted mortality ratios of female cigarette smokers, by number of cigarettes smoked per day and age began smoking. Subjects aged 45-54 at start of studs. 25-Stat.e Studs Number of cigarettes wr dav Age began smoking 25+ 524 Nonsmokers 1.00 1.00 l-9 0.95 0.88 l&19 1.17 1.23 2x39 1.33 1.61 40+ o ? 1.65 SOURCE: Hammond, E.C. (I?). TABLE 28.-Age-adjusted mortality ratios of female cigarette smokers, by number of cigarettes smoked per day and degree of inhalation and age. 25-State Study Dw= Age of inhalation 3544 4554 5544 f&74 7544 Nonsmokers 1.00 1.M) 1.00 1.00 1.00 None t* 1.01 1.11 1.12 0.96 Slight 1.22 1.21 1.28 1.26 1.21 Moderate 1.05 1.36 1.32 1.41 .* DeeP 1.40 1.78 1.64 ** o ? SOURCE: Hammond, E.C. (I 7). United States. Smokers are now asking the question: "Will it help me if I quit smoking ?" Some of the first evidence concerning death rates in ex-smokers required explanation. The data from the Hammond and Horn study of men in nine States are presented in Table 29. It can be seen that the mortality ratios of ex-smokers were higher in the first Year after quitting than for continuing smokers. After the first year, 2-27 TABLE 29.-Age-adjusted mortality ratios for males who are ex- smokers of cigarettes, by former amount smoked per day and years since stopped smoking. Males in nine St&?S Years since stopped smoking Cigarettes formerly smoked per day 1-19 20+ 0 (Smokers) 1.61 202 Under 1 204 269 l-10 years 1.30 1.82 10+ years 1.08 1.60 SOURCE: Hammond, E.C. (m). however, death rates for ex-smokers fell progressively so that after 10 years the former smokers of 1 to 19 cigarettes had a mortality ratio of only 1.08. The explanation for the higher death rates in the 1st year after quitting is found in the fact that both healthy and sick individuals quit smoking. The higher mortality ratio is experienced by those who quit because of illness and not by those who quit for better health. In the study of U.S. veterans, a differentiation was made between ex- smokers who stopped smoking on the recommendation of a doctor and those who quit for other reasons. About 10 percent of the smokers quit on doctors' orders; this group had much higher mortality ratios than those who stopped for other reasons. These data are presented in Table 30, where the mortality ratios for ex-smokers by "years since stopping smoking," "maximum amount smoked," "age began smoking," and "reason for quitting" are examined. There is a direct relationship between mortality rates and the maximum amount smoked, an inverse relationship between mortality and "years since stopped smoking," and also an inverse relationship between mortality and "age began smoking." A detailed analysis of the mortality experience of ex-smokers who stopped for reasons other than doctors' orders is given in Figures 1 through 4. This information is on ex-smokers, aged 55 to 64, from the 1954 cohort of the U.S. Veterans Study, who formerly smoked from 21 to 39 cigarettes per day. "Years since stopping smoking" is considered as a variable and the mortality rates are compared with those of current cigarette smokers and nonsmokers. Annual probabilities of dying are plotted on a logarithmic scale. This results in a fairly smooth and linear pattern for both smokers and nonsmokers. These lines also appear to be parallel, or perhaps to diverge slightly. This indicates an approximately constant or slightly increasing excess risk of dying 2-28 TABLE 30.-Mortality ratios of ex-smokers of cigarettes only who quit smoking on doctors orders and for other reasons, by certain dosage variables. U.S. veterans 1954 cohort, N-year followup Years since stopped smoking Mortality ratice Years Quit for since WriOUS stopped reasons <5 1.23 59 1.23 w14 1.14 lSl9 1.04 >19 1.96 Total 1.18 Quit on doctors orders 1.55 1.43 1.n 1.35 1.16 1.52 Number of cigarettes per day Mortality ratios No. of cigarettes per day a Total Quit for Quit on WlriOUS doctors rea9Ons orders 1.00 1.42 111 1.48 1.30 1.53 1.32 1.60 1.18 1.52 Age started smoking Mortality ratios Quit for various R?aSOIlS Quit on doctors orders (15 1.36 1.59 lC19 1.20 1.55 m-24 1.12 1.49 >a 1.15 1.34 Total 1.18 1.52 SOURCE: Roget, E. (33). among smokers, compared to nonsmokers over the 16-year period. It would be expected that the mortality experience of ex-smokers initially would be similar to that of smokers, but with the passing of time the mortality risk should move progressively closer to that of nonsmokers. Figure 1 illustrates this. For ex-smokers who quit less than 5 years prior to the beginning of the study, the mortality risk is at 2-29 first nearly identical to that of smokers. Over the years, the risk gradually falls to a position approximately halfway between that of smokers and nonsmokers. Figures 2 and 3 show that with longer periods of cessation the mortality risk continues to approach that of nonsmokers. In Figure 4, it can be seen that for ex-smokers who had been off cigarettes for 15 or more years before the start of this study, their mortality risk fluctuates about the mortality risk of nonsmokers for the entire E-year period. The mortality experience of British doctors who were ex-smokers is examined in Table 31. These data indicate that there are definite benefits from quitting smoking no matter how long one has smoked. After 10 to 15 years, ex-smokers have a risk of dying that is similar to that of those who have never smoked. The risk of dying from ischemic heart disease decreases rapidly immediately after stopping smoking, whereas the risk of dying from lung cancer decreases more slowly. Overall mortality measures the net benefit of quitting and, therefore, drops more slowly than do death rates for certain disease categories. Mortality and Pipe and Cigar Smoking Pipe and cigar smokers have mortality rates that are similar to those of cigarette smokers for cancers of the oral cavity, pharynx, larynx, and esophagus. Pipe and cigar smokers have much lower death rates than cigarette smokers for cancer of the lung, ischemic heart disease, and chronic obstructive lung disease. Since these last three disease categories account for the bulk of the excess mortality associated with cigarette smoking, pipe and cigar smokers experience overall mortality rates that are much lower than cigarette smokers. Inhalation of smoke is necessary to expose the heart and lungs to the harmful constituents found in tobacco smoke, and pipe and cigar smokers report much less inhalation of smoke than cigarette smokers. Pipe smoke and cigar smoke contain nearly all the same chemical compounds found in cigarette smoke, but pipe and cigar smoke tends to be alkaline in pH rather than acid as is cigarette smoke. Alkaline smoke is irritating to the respiratory tract. This is likely to be an important reason why pipe and cigar smokers report a much lower level of smoke inhalation than cigarette smokers. Table 32 summarizes the mortality ratios for male smokers by the type of tobacco used for the five studies that obtained data on pipe and cigar smoking. Cigar smokers have overall mortality ratios that are from 6 to 25 percent higher than nonsmokers. Mixing cigarette smoking with pipe or cigar smoking substantially increases the mortality ratios, although they remain somewhat less than the mortality ratios of cigarette-only smokers. Dose-response relationships between overall mortality and the amount of tobacco smoked were examined in several studies. Data 2-30 w 9.0 6.0 7.0 6.0 5.0 4.0 3.0 !!! < 2.0 2 4 f LE 8 & 1.0 8 0.9 g 0.5 1 0.7 8 0.6 i 0.5 3 0.4 0.3 0.2 0.1 0 - - 0 Never Smoked - Ex-c@am6e znwhem stopped ka lhan 5 years ego ??????? o wuntsmoked,21-39 cigsfenes per day. - Cunent dgamtle smokets. Smokii21-39cignemnp3fday 1 2 3 4 5 6 7 6 9 10 11 12 13 14 16 16 YEARS OF FOUWWP FIGURE l.-Annual probability of dying for ex-smokers who quit smoking less than 5 years, current cigarette smokers and nonsmokers, aged 55-64, U.S. veterans 1954 cohort, 16-year follow-up SOURCE: Rogot,~.(SS). 2-31 QX 9.0 0.0 7.0 6.0 5.0 4.0 3.0 ul g 2.0 8 8 9 ii g 1.0 ij 0.9 c 0.6 2 $ 0.7 f. 0.6 a 0.5 z 4 0.4 0.3 0.2 . 0.1 O---O Never.Smo@d Maximum emounr smoked 21-39 cigarenes per day. - currenl cigerelle aokefs. smoking 21-39 oigamnes Pm day. I I 1 I I I I I I I I 1 1 1 1 1 , 2 3 4 5 6 7 0 9 10 11 12 13 14 15 16 MARS OF FOLLOWUP FIGURE 2.-Annual probability of dying for ex-smokers who quit smoking 5-9 years, current cigarette smokers and nonsmokers, aged 5&64, U.S. veterans 1954 cohort, X-year follow-up SOURCE: Rogot, E (SJ). 2-32 9x 8.0 0.0 7.0 6.0 5.0 ly , - I - 4.0 3.0 , - I - I - I - , _ , - , - I - 0.3 0.2 0.1 . 0 w o---O NwerSmoked m Ex-olgemlle unduns stopped 10-14 years Maximum amount mmked 21-39 cigaMte6 wr day. I I I I I I I I I I II I I I) 1 2 3 4 5 6 7 0 Q 10 11 12 13 14 15 16 YEARS OF FOLlOWUP FIGURE S.--Annual probability of dying for ex-smokers who quit M-14 years, current cigarette smokers and nonsmokers, aged 5W, U.S. veterans I954 cohort, IS-year follow-up SOURCE: *t, E. (88). 2-33 v 9.0 8.0 7.0 6.0 5.0 4.0 3.0 !Y 5 ij 2.0 g E P ii :.c 8 0.E c 0.e 1 0.i E 0.E 3 0.5 f 0.4 0.: o---ONeversmoked 9----8 Ex-cgmne 8moh8rs Stopped 15cwmoreyeamago Maximum mnolmt mwked 21-36 cigsrs4tes psr day. m Current c4gnrett8 smokers. Sting 21-39 cigarettes pa d8y. I I I I I I i I I I I I I I I I 1 2 3 4 5 6 7 8 `9 ii 11 12 13 14 15 16 YEARS OF FOLLOWUP FIGURE I.-Annual probability of dying for ex-smokers who quit 15+ years, current cigarette smokers and nonsmokers, aged 55-64, U.S. veterans 1954 cohort, N-year follow-up SOURCE: Rqot, E. (3s). 2-34 TABLE 31.-Mortality ratios of ex-smokers compared to nonsmokers, by age and number of years since stopping smoking. Study of British doctors Years since Mortality ratios stopping Age Age All smoking a64 6.5+ ages 0 (Cumen~ smokers) 20 1.6 1.8 1-4 1.7 1.4 1.5 69 1.6 1.4 1.5 US-14 1.4 1.2 1.3 15+ 1.1 1.1 1.1 Nonsmokers 1.0 1.0 1.0 SOURCE: Doll. R. (8). TABLE 32.-Mortality ratios for male smokers, by type of tobacco used Study Men in 9 States(20) British Docto~4) Canadian Veterans(f) U.S. Veterans(26) Males ir. 25 States(l7) Non- Cigar smoker only 1.00 1.22 1.00 .I 1.00 1.06 1.00 1.16 1.00 1.25 pipe only 1.12 ** 1.05 1.07 1.19 Cigar & Pipe 1.10 1.09 0.93 1.08 1.01 Cigarette & cigar Cigarette or pipe 0ttly 1.43 1.63 1.31 1.73 1.13 1.54 1.51 1.55 1.57 1.36 from the study of men in nine States, Canadian veterans, and the ACS 25-State Study are presented in Tables 33 through 35. There is a dose- response relationship evident for cigar smoking that is small but found consistently. There was no clear dose-response relationship for pipe smoking. Data from the U.S. Veterans Study are presented in Tables 36 through 39. Again, there appears to be a dose-response relationship for cigar smoking, both for the number of cigars smoked per day and for the age began smoking cigars. For pipe smokers, a dose-response relationship was found for the number of pipefuls per day, but not for the age began smoking. The U.S. Veterans Study (31) contains the most detailed information on pipe, cigar, and cigarette smoking in various combinations and in various sequences. These data on mortality ratios are shown in Table 40 and have been arranged by "increasing risk of mortality." The first section shows the mortality experience of current cigarette smokers by the present, past, or nonuse of pipes and cigars. Cigarette smokers who have the lowest mortality ratio of 1.21 are those who also currently smoke both pipes and cigars. Current cigarette smokers who formerly smoked pipes and cigars have a mortality ratio of 1.48, which is only 2-35 TABLE 33.-Age-adjusted mortality ratios for male cigar and pipe smokers, by amount smoked. Males in nine States Type and amount smoked ratio Nonsmokers Cigar only l-4 per day 4+ per day All cigar smokers 1.00 1.03 1.24 1.09 Pipe only l-10 pipefuls per day lO+ pipefuls per day All pip smokem 1.05 1.19 1.09 SOURCE: Hammond. E.C. (SO). TABLE 34.-Age-adjusted mortality ratios for male cigar and pipe smokers, by amount smoked. Canadian veterans Type and amount Mortality smoked ratio Nonsmoker Cigar only l-2 per day t10 per day 1.00 1.14 1.19 pipe only l-10 pipefuls per day IO+ pipefuls per day 1.01 1.00 SOURCE: Best, E.W.R (I). slightly below the mortality ratio of 1.55 of cigarette-only smokers who have never smoked pipes or cigars. The second section of Table 40 shows that the mortality ratios of current cigar smokers are slightly decreased among those also currently smoking pipes and significantly increased among those also currently smoking cigarettes. The third section shows that pipe smokers with the lowest mortality are those who have never smoked cigarettes or cigars. Mortality ratios increase slightly with the addition of current cigar smoking and jump moderately with the addition of current cigarette smoking. 2-36 TABLE 35.-Age-adjusted mortality ratios for male cigar and pipe smokers, by amount smoked. Males in 25 states Type and amount smoked Mortality ratio NonsmokeR Cigar only 14 day per 4+ per day All cigar smokers 1.00 1.03 1.18 1.09 pipe only l-9 pipefuls per day 9+ pipefuls per day All pipe smokers SOURCE: Hammond, EC. (I?). 1.08 0.92 1.04 TABLE 36.-Age-adjusted mortality ratios of current smokers of cigars only, by amount smoked. U.S. veterans 1954 cohort, 16year followup No. of cigars per day Mortality ratio Nonsmokers 1.00 l-2 1.11 5-4 1.13 54 1.22 9+ 1.39 Total 1.16 ~URCE: Roget. E. (33). TABLE 37.-Age-adjusted mortality ratios of current smokers of cigars only, by age began smoking. U.S. veterans 1954 cohort, H-year followup Mortality ratio Nonsmokers 1.00 <15 1.22 15-19 1.23 20-24 1.16 >a 1.13 Total 1.16 mURf% Rc@, E. (33). Mortality by Cause of Death The underlying cause of death was obtained from the death certificate 2-37