Lung Cancer and Smoking Trends in the United States Over the Past 25 Years LAWRENCE GARFINKEL AND EDWIN SILVERBERG Department of Epidemiology and Statistics American Cancer Society New York, New York 10036
Lung cancer is the leading cause of cancer incidence and death in the United States. The American Cancer Society estimated that there will be 157,000 new cases of lung cancer diagnosed in 1990 and 142,000 deaths.' Death rates in men have shown a remarkableincreasein the last 5Oyears paralleling arise in cigarette smoking20 years earlier. Age-adjustedlungcancerdeathratesinmenintheunited Statesgrew from 11per 100,000population in 1940 to 73 per 100,000 in 1982. Since then the rate has leveled off. In 1986,it was 74. The lung cancer rate in women started to rise in the early 1960s from 6 per 100,000 to 25 per 100,000in 1986 adjusted to the total U.S. population in 1970. Lung cancer rates in young men age 35-44 started to decline in the 1970s and in men age 45-54 in the early 1980s. There has been a leveling off of mortality rates in men aged 5 5 4 4 . It is only in the oldest age groups that a steady increase in rates has been observed through 1986 (FIG.1). These trends indicate that there should be a decrease in the overall lung cancer mortality rate in men by the early 1 9 9 0 ~Among .~ women the age-specific rates continue to increase, except for age group 35-44, where adecrease has beenseenstartingintheearly 1980s,andalevelingofratesinagegroup 45-54 (FIG.2). In addition to a decrease in mortality trends, the incidence of lung cancer has also declined. Studies of lung cancer incidence by the SEER Program of the National Cancer Institute reveal that the annual percent increasein men between 1975and 1979 was l.6%, but between 1982 and 1986, there was an annual percent decrease in incidence rate of 0.8% .3 The rate in whites decreased by 0.9% annually during this period but increased by 0.8% in blacks. Among women the annual rate of increase diminishedfrom6.3% inthe 1975-1979period to2.8% in 1982-1985. In black women however, there was no change in the annual rate of increase in the two periods, 8.4% and 8.57'0, respectively. Cigarette consumption per capita in persons age 18 and older measures total cigarette consumption divided by the estimated population and includes nonsmokers and exsmokers as well as smokers in the denominator. The index rose steadily from 1,085in 1925to 3,886 in 1952. Following publication of the smoking-health reports in the early 1950s, the index dropped 9% to 3,546 in 1954. It then continued to rise until 146
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1963 when it reached 4,345. With the publication of the first Surgeon General’s Report on smoking in 1964, the index dropped 4.5% to 4,194.It rose again to 4,287 in 1966. During 1969-1971, another drop of 5% accompanied the anti-smoking advertising on television. When these ads were removed the index climbed again to a high of 4,148in 1973. Since then in association with the growth of the nonsmoker movement and anti-smoking legislation restricting smokingin publicplaces, there has been a steady decIine to 2,936 in 1989,the lowest level since 1942.4 This decline is related to the leveling off of lung cancer mortality rates.
75+
65-74
55-81
ALL AGES
4544
3
w
FIGURE 1. Male lung cancerdeath rates, United States (19504951‘0 1984-1985). Standardized on the age distribution of the population of the United States, 1970.
Data on the prevalence of cigarette smoking have been collected by the National Health Survey of the National Center for Health Statistics every several years since 1965. The percent of men who smoked cigarettes decreased from 50.2% in 1965 to 31.8% in 1987.’ In women, cigarette smoking also decreased from 31.9% in 1965 to 26.8% in 1987(FIG.3). Cigarette smoking is more common in blacks than in whites. In 1987.32.9% of blacks and 28.5% of whites were current smokers, although whites smoke more cigarettes per day. The largest differences in smoking are seen between educational groups. There was little difference in 1965 in the percent of cigarette smokers between those with less than a high school education (36.5%) and college graduates (33.7%). However in 1987,35.7% of those with less than a high school education smoked while only 16.3% ofcollegegraduatessmoked,adropofmorethan 50%. Amonghighschoolgraduates,33.1% smokedcigarettesandin thosewithsome college education, 26.1Y0smoked. It is estimated that by the year 2000 if present
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65-74
75r 5564
4554 ALL AGES
35-44
* - ,------
trends continue that only 22% of the adult population will be smoking and that only 10% of collegegraduates will be cigarette smokers .6 This indicates that quit-smoking messages are reaching better educated groups to a greater extent than those with less education. Further evidenceof changesin smokingpattenscan be seen by comparing smoking distribution age-standardized to the population of U.S. women over age 35 in 1970in two American Cancer Society prospective epidemiologic studies of middle class volunteers in 1959 and 1982. The first, Cancer Prevention Study I (CPS I), included 1,078,000 persons enrolled in 25 states. The second, Cancer Prevention Study 11, included 1,200,000subjects in all 50 states. The subjects were basically the same type: mostly middle-class Americans ages 30 and older, enrolled by volunteers of the American Cancer Society. More than 98% of subjects enrolled in CPS I were traced (alive or dead) over a 12-year period. In CPS 11,subjects have been traced so far for 4 years (1982-1986). In CPS I in 1959,48.4% of men smoked cigarettes. In CPS IT, in 1982, the percent of smokers had dropped to 24.4%. Ex-cigarette smokers comprised 41.4% in CPS I1 and less than half that percentage (17.3%) in CPS I. Among women, more reported they had ever smoked in CPS I1 (43.6%) than in CPS I (32.8%), and a larger percentage were current smokers (27.2%) than in CPS IT (21.5%). Butthepercentex-cigarettesmokerswas22.1Y0in CPSIIand5.6% inCPS I, about four times as high. During the period of these two American Cancer Society studies, the relative risk of lung cancer in women smokers compared to nonsmokers increased dramatically. This is illustrated by the data in TABLE 1. Age-standardized rates are shown for three 4-year periods in CPS I and for one 4-year period (1982-1986) in CPS 11. The rate for
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nonsmoking females remained fairly constant over the 26-year period, about 12 per 100,OOO. However the lung cancer rate in cigarette smokers rose from 23.9 in 19601964, to 36.5 in 1965-1968, to 54.0 in 1969-1972, and to 130.4 in 1982-1986. The relativerisksforcigarettesmokersroseoverthat periodoftimefrom2.0, to2.9, to4.5, to 10.8.’ In men, the lung cancer rate in nonsmokers standardized to the U.S. population age 35 and over was about 15 per 100,OOO over the four periods, but the relative risks for cigarette smokers rose from about 9 in each of the three periods in the earlier study to 17.4 in CPS 11. The major reasons for the increase in relative risks in women are illustrated in TABLES 2 and 3. TABLE 2 shows the percent of women who reportedly smoked 20 or more cigarettedday in CPS I and CPS 11, by age group. In each age group, there was a far higher percentage of smokers who smoked 20 or more cigarettedday in CPS I1 than in CPS I; with an absolute average difference of 20.6%. Similarly, the average age began smoking for CPS I1 subjectsdecreased 3.3 years at age 4 5 4 9 compared to CPS I, and the difference was 10.1 years at age 65-69. Overall the age-adjusted differenceinage begansmokinginCPSIIwas7.2yearsyoungerthaninCPS I.9These differencesin exposure help to explain the large increases in relative risks in smoking women. In addition, a larger proportion of women in the third period of CPS I were smokers and smoked more heavily compared to women of the same attained ages in the first and second 4-year periods. Relative risks in CPS I1 also increased according to the number of cigarettes smokedlday. They rose from 5.5 to 1for those who smoked 1to 10cigarettedday; to 11.2for 11to 19cigarettedday; 14.2for20cigarettes/day;20.4 for 21 to30cigarettedday; and 22.0 for 31 or more cigarettedday. These relative risks are similar to those seen in men in CPS I. Since the early 1950s,American cigaretteshave undergone many changes,with the
so
-
40
..
s 30-
. . I -
-----FEMALES
20
-
10
-
n
I
I
I
I
I
I
I
I
I
I
I
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Age-Standardized Rates in Smokers and Nonsmokers and Relative Risks over Time, by Sex
TABLE I.
Cancer Prevention Study I
1960-1964
1965-1968
Cancer Prevention Study I1 ___ 1969-1972 1982-1986
Females Never smoked Cigarette smoker Relative risk
11.7 23.9 2.0
12.4 36.5 2.9
12.2 54.0 6.5
12.1 130.4 10.8
Males Never smoked Cigarette smoker Relative risk
14.6 137.0 9.4
16.6 154.0 9.3
16.7 160.6 9.6
15.4 267.9 17.4
Rates are standardized to the age distribution of the U.S. population, 1970.
introduction of filter-tip cigarettes in the mid-l950s, specially processed tobacco to reduce tar and nicotine, introduction of new brands, perforated cigarette paper, etc. The percent of plain-tipcigarettes has dropped to an estimated4% of the total market in 1989. Tar and nicotine levels have fallen steadily for the past 35 years. In 1982 according to data in CPS 11, cigarettes brands with less than 10 mg of tar comprised 25.1% ofcigarettebrandssmokedbyrnen,and33.1% ofthosesmoked bywomen. On theother hand,cigaretteswith 20or moremg tarweresmoked by 16.1%of males and only6.2% of females.’ In 1959,when data from CPS I were collected, more than 88% ofmen and78% ofwomensmokedcigaretteswith20ormoremgtar~andbrandswith less than 10 mg of tar made up less than 1%of the total market.” An analysis of data from CPS I has shown that persons smoking cigarettes with relatively low tar and nicotine had a reduction in lung cancer of about 25% compared to those smoking high tadnicotine cigarettes. This study matched subjectsin number of cigarettes smoked, age began smoking, and seven other variables to compare lung cancer mortality in high, medium, and low tadnicotine smokers. Smokers of “low” tar cigarettes smoked cigarettes with less than 17.6 mg tar; “high” tar included those w h o TABLE 2.
Percent of Smokers Smoking 20+ CigarettedDay Women
Age Group (Yo.)
Cancer Prevention Study I (Yo)
4549 50 -54 55-59 60-64 65-69 70--74 75+ Age-adjusted Difference
44.6 42.7 39.9 36.3 31.9 26.7 23.8
Cancer Prevention Study I1
Absolute Difference (Yo)
(1%)
63.2 62.4 61.0 58.4 53.1 47.1 45.1
18.6 19.7 21.1 22.1 21.2 20.4 21.3 20.6
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smoked cigarettes with 25.8 or more mg and “medium” tar were those in between. Therewasaconsistent dropin thelungcancerrate from high tomediumtolow in both males and females over two 4-month periods of time.” It should be recognized that what was called “low” tar in 1959 would be classified as “medium” tar in the 1980s. Another analysis from these data showed that smokers of “low” tar cigarettes who smoked 20 to 39 cigaretteslday had lung cancer rates 71% higher than smokers of “high” tar cigarettes who smoked less than 20 cigarettes a day.12 This analysis therefore showed that tar level was less important in lung cancer rates than the number of cigarettes smoked per day. In an analysis of the relative risk of lung cancer by tar content of cigarettesin CPS 11,it was also found that there was an increasing increment associated with increasing tar exposure in women, holding number of cigarettes and age began smoking ~ o n s t a n tThe . ~ relative risks of smoking cigarettes with tar yields 5,10,15, and 20mg compared to nonsmokers were 1.17,1.36,1.59, and 1.85, respectively.
TABLE 3
Average Age Began Cigarette Smoking Women
Age Group
Cancer Prevention Study I
Cancer Prevention Study 11
Absolute Difference
22.7 25.3 28.6 30.8 32.2 32.7 33.3
19.4 20.0 20.8 21.7 22.1 24.3 27.4
3.3 5.3 7.8 9.1 10.1 8.4 5.9
45-49
50-54 55-59 60-64
65-69 70-74 75+
Age-adjusted Difference
7.2
Previously, we found that lung cancer rates decrease when subjects stopped smoking. The rates were highest in those who quit less than one year before the study began. This group is weighted with sick people who quit because of disease. But rates start to decrease after 1year of cessation and by the time smokers have quit for 10 or more years, the lung cancer rate approaches that of persons who never smoked; for heavy smokers some risk remains.13 We found similar patterns in women who reported they quit smokingin CPS 11. Inwomen who had smoked21 ormorecigarettes/ day, rates were 21.2 times higher in current smokers thanin nonsmokers and 32.5 times higher in those who quit up to 2 years before the study began. The relative risks dropped to 20.3 for those who quit 3 to 5 years, 11.4 for those who quit 6 to 10 years, and 4.0 for those who quit 11or more years before the study began (FIG.4). As cigarette smoking is slowly being brought under control, another matter of great concern has risen. TBLE4 shows that while domesticconsumption has continued to decrease over the last eight years, total production of cigarettes has increased in the past four years. This is because of a 130% increase in exports over the past five years, from 56.5 billion to 130.0 billion in 1989. Exports now comprise 19% of total cigarette production. While our efforts to control smoking in the United States have been succeeding, tobacco companies are shifting their attention to overseas markets.
c
t01 4
21 or More Cigarettes a Day
@
FIGURE 4. Relative risks in ex-smokers, by number of years quit. Women, Cancer Prevention Study 11.
1-20 Cigarettes a Day
1.o
B
1.o
B
13.6
21.2
32.4
GARFINKEL & SILVERBERG: LUNG CANCER AND SMOKING TRENDS TABLE A
Year
1981 1982 1983 1986 1985 1986 1987 1988' 1989.
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Cigarette Production in the United States and Exports 1981-1989 Production (Billions)
736.5 694.2 667.0 668.8 665.3 658.0 689.6 694.5 685.0
Exports
Number (Billions)
%
82.6 73.6 60.7 56.5 58.9 64.3 100.2 118.5 130.0
11.2 10.6 9.1 8.4 8.9 9.8 14.5 17.1 19.0
Annual Change Domestic Consumption
+1.3% -0.9 -5.6 +0.7 -1.1 -1.7 -1.5 -2.2 -3.6
Data from Tobacco Situation and Outlook Report, US. Department of Agriculture, September 1989. *Preliminary estimate.
DISCUSSION Data from this study indicate that attempts to control cigarette smoking in the United States are succeeding and the efforts of researchers, public health educators, cancer control officials, physicians, lobbyists, etc. have all come together to have a visible impact on smoking rates and lung cancer mortality rates in men. Successwill take somewhat longer in women because of rapid rate of increase in smoking over the past several decades but some evidence of successin controlling smoking is apparent in women, especially younger and better educated women. Smoking prevalence has dropped by more than 50% in college graduates and it is in thisgroup wheresmokingcontrol methods have had their greatest success. Efforts now have to be concentrated on those with less than a high school education to persuade them not to smoke. There has been little change in the percent smokers in this group since 1965. A larger percentage of blacks smoke than whites, but they tend to smoke fewer cigarettes per day.I4 Yet blacks continue to have lung cancer rates about 40% higher than whites. This factor is worthy of further study to determine the reasons for this fact. Of major concern is the trend for more shipments of cigarettes overseas. Cigarettes shipped abroad do not come under the U.S. laws for labeling of tar and nicotine content and are, in general, higher in tar yields than cigarettes sold in the United States. Efforts by cancer control authorities and legislative activists are being extended to deal with this growing problem.
REFERENCES
1. SILVERBERG, E., C. S. BORING & T. S. SQUIRES. 1990.Cancer Statistics.1990.CA 40: 9-26. 2. DEVESA, S. S., W. J. BLOT& J. F. FRAUMENI, JR. 1989.Declining lung cancer rates among
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3.
4. 5. 6. 7.
8. 9. 10.
11.
12.
13. 14.
ANNALS NEW YORK ACADEMY OF SCIENCES young men and women in the United States: A cohort analysis. J. Natl. Cancer Inst. 81: 1568-1571 E. SONDIK & Office on Smoking and Health, Center for Chronic RIES,L. A,, B. R. EDWARDS, Disease Prevention and Health Promotion. 1989. Trends in lung cancer incidence, U.S. 1973-1986. Morbid. Mortal. Weekly Rep. 38: 505-513. U.S. Dept. of Agriculture, Economic Research Service. 1989. Tobacco Situation and Outlook, TS-208. Sept. 1989. U.S. PublicHealth Service. 1989. Reducing the Health Consequencesof Smoking: 25 Ycars of Progress. A Report of the Surgeon General. DHHS Publication No. (CDC) 89-8411. U.S. Dept. of Health and Human Services. Washington, D.C. E. J. HATZIANDREU & R. M. DAVIS.1989. Trends PIERCE,J. P., M. C. FIORE,T. E. NOVOTNY, in cigarette smoking in the United States: Projections to the year 2000. JAMA 261:6165. GARFINKEL, L. 1985. Selection, follow-up and analysis in the American Cancer Society’s prospective studies. Natl. Cancer Inst. Monog. 67: 49-52, STELLMAN, S. D. & L. GARFINKEL. 1986. Smoking habits and tar levels in a new American Cancer Society prospective study of 1.2 million men and women. J. Natl. Cancer Inst. 76c 1057-1063. GARFINKEL, L. & S. D. STELLMAN. 1988. Smoking and lung cancer in women: Findings in a prospective study. Cancer Res. 48:69514955. E. C. & L. GARFINKEL. 1961.Smoking habits of men and women. J. Natl. Cancer HAMMOND, Inst. 27: 617-631. HAMMOND, E. C., L. GARFINKEL, H. SEIDMAN & E. A. LEW.1976. “Tar” and nicotine content of cigarette smoke in relation to death rates. Environ. Res. 12:263-274. E. C., L. GARFINKEL, H. SEIDMAN & E. A. LEW.1977. Some recent findings HAMMONU, concerning cigarette smoking. In: The Origins of Human Cancer. H. H. Hiatt, J. D. Watson & J. A. Winsten, Eds. A: 101-112. Cold Springs Harbor Laboratory. New York. HAMMOND, E. C. 1966. Smoking in relation to the death rates of onc million men and women. Natl. Cancer Inst. Monogr. Sk 127-204. SCHOENBORN, C. A. & B. H. COHEN.1986. Trends in smoking, alcohol consumption and other health practices among U.S. adults, 1977 and 1983. Advance Data from Vital and Health Statistics, No. 118. DHHS Publication No. (PHS) 86-1250. National Center for Health Statistics. U.S. Public Health Service. Washington, DC.
DISCUSSION
ANTHONK MAZZOCCHI (Oil, Atomic, and Chemical Workers Union, AFL-CIO): I would hope that investigators in the future will look into occupational factors more carefully. It may be that less educated people are doing more stressful work and it’s much more difficult to quit. Also, the trend in the United States of increased daily hours of work may increase stress and smoking. More people work 16 hours straight now than ever before, and I would hope that you begin to factor that trend into future studies. LAWRENCE GARFINKEL: One of the things we’re going to do is find o u t whether 01 not people work swing shifts and how much stress they are under at work. Then we’ll take that into consideration when we get to that analysis. JOELSCHWARTZ ( U S . Environmental Protection Agency, Washington, D C ) :Your second figure shows the time trends by different age groups. Dr. Davis and I noted a coupleofyearsago that ifyoulookat where theinflection point started tocurvedown in the age 35 to 44cohort and then you look at the inflection point where it’s beginning
GARFINKEL & SILVERBERG LUNG CANCER AND SMOKING TRENDS
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tocurvedownin theage45 to54cohort, thedeclineisshowing up 10yearslaterin the 10-year older group. This goes back to a previous comment about cohort effect. GARFINKEL: That ties in very nicely with the percent smokers by the way. MARVINS~DERM AN (NationalResearch Council, Washington,DC):I share your pleasure and delight at these rates decreasing and at thenumber of cigarettessmoked decreasing. There are two other things I would like to see. Cigarettes smoked these days contain less tobacco than they did in the past. When I first started looking at cigarettes30yearsagotheymade230cigarettesto thepoundof tobacco. Inthe United States, they are now making 400 cigarettes to the pound of tobacco. Slim cigarettes really are slim. If you could put that in with your cigarette consumption, we ought to show much greater decreases. But what concerns me, having mentioned this, are two things. I hope you have enough data on blacks to look at this. Black males have 40 to 50% higher lung cancer rates than white males. The proportion of black smokers is roughly 5% higher than white smokers, yet the amount blacks smoke is less on the average, substantially less. The age of starting to smoke among the blacks is older than among the whites. Yet, there is this 40 to 50% increase in lung cancer rates. The rates for black women and white women are almost identical and black women smoke 70 to 75% as much as white women. I had hoped that your data would be enough to elucidate these differences. What else is going on? I realize yours is a middle class population and not a working class population and more suburban than central city urban. Let me add some comments concerning American Cancer Society (ACS) nonsmokers lung cancer rates. These rates do not seem to me to be applicable to all of the U.S., mostly because the ACS sample is unrepresentative. Because of changes in the tar and tobacco content of cigarettes since the 1960s, the risk of lung cancer per cigarettesmokedshould bedeclining. The ACSshowsthe risk asincreasing. The CPS I1 sample is more white, more white collar, and more suburban than the U S. population. Since lung cancer rates are higher among blacks, blue collar (industrial) workers, and central city (higher urban) dwellers, the rates for non-smokers as reported by CPS I1should be biased downward, and lower than the rates would be for a representative sample. Because cigarettes since 1960 have contained less tar, tobacco, and nicotine per cigarette, it is reasonable to conclude that the toxic responses (i.e., lung cancer) per cigarette would decline over time. The Hammond-Horn data and the Dorn (American veterans) data both showed that the relative risk (RR) for lung cancer per cigarette smoked was loosely approximated by the formula RR = 1 + 0.52d. where d is the number of cigarettes smoked per day. The most recent CPS II data would be better fit by the equation RR = + 0.8d, which indicates about 60% increase in “potency” (for producing lung cancer) per cigarette (i.e.,0.8/0.5 = 1.6). In addition to the lower tobacco content and the yield of tar per cigarette, there has been a very substantial switch to filter cigarettes, which, according to early reports (Wynder and Bross, for example) reduced the toxicity per cigarette.
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If the non-smoker lung cancer rates had been higher than reported by CPS I1 (i.e.. increasedfromCPS1 to CPSII) then the reportedrelative riskper cigarettewould not have increased, and might, in fact have declined, as the external evidence would suggest should have happened. What has happened instead is that the CPS I1 data imply that with lower tar filter cigarettes and fewer persons smoking cigarettes, the smoking attributable fraction (SAF) of lung cancers has increased:
25 Years Ago
5 to 10 Years Ago
If R R = 1 + .5d
1 + .8d 25
20
d Proportion smoking (p) SAP
.50 - .60 .83 .86
.35 - .45 ,875 .90
w 1) ”Excluding contributions by exsmokers, SAF = 1 1)
+m-
Thusit would have to be argued that withreducedsmoking and withless hazardous (lower tar, lower tobacc0,filtered) cigarettes, the proportion of lung cancer attributable to smoking has increased at the same time that total rates have decreased or remained stable. However, C. C .Brown and L. G. Kessler argue in a recent paper (J. Nutt. Cancer Znst. 1988,80:43-51) “...recent trends in lung cancer are unlikely to be affected by changes in cigarette composition and consumption in the near term...”. A more reasonable conclusion is that the ACS relative risks are too high, in part because ACS has underestimated the non-smoking related lung cancers, which have gone up in the interval between CPS I and CPS 11. GARFINKEI.: I don’t know if we have enough blacks to look at mortality rates without following them for a longer period of time. We have about 50,000 blacks in the study which, you know, sounds like a lot. But when you’re looking at mortality rates for a specific disease, it may not be sufficient. The other thing that I think you should be aware of is that the blacks in our sample population are middle class blacks. There are very few of the working class blacks. So I don’t know if a thorough analysis of our data will ever elucidate the effects of smoking on working class blacks. NO RE KoHLMEIER(znstirUfe~oeforSOciaIMedicineund Epidemiology,Berlin, l?R. G.): There are risk groups that we have to watch closely. I think one of them might also be the heavy smokers. In Germany, the picture may be very different than in the United States. We just did an analysis of the structural trends. Although we have a bit of a reduction in smoking, it is not comparable with the United States. Those people who smoke a lot are smoking more. That means not only in terms of t h e number of cigarettes, but in terms of the amount of exposure they’re getting to nicotine, tar, and other substances. So if you look at these special groups of heavy smokers, do you see the same trend in the United States as we’re seeing in Germany? The second issue is people with college degrees and smoking. Those are populations that have changedradically,haven’t they? When you started looking, there were fewer people who went to college. So the result is actually much more positive because more of the population is getting a college degree and more of them are not smoking. There is something dynamic going on there. I think it’s important to point out that if you’re talking about cigarette GARFINKEL:
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smokers over a long period of time, cigarette smokers in recent years contain a much heavier portion of heavy smokers because it’s the light smokers who have quit. The people who continue are heavier smokers. SCHWARTZ: In some of the SYSTAT graphs we produced you see a very strong cohort effect in terms of lung cancer in the older age groups. And, in fact, the cohort with the highest mortality rate at any given age is not the cohort that has the highest rate of smoking. It’s the cohort that was born around 1895. You can see this nice little diagonal ridge marching across those three-dimensional plots. GARFINKEL: Well, this may differ in different countries. But in the United States whenwedidour studyin 1959thehighestpercentageofsmokerswerethosewhowere born just before the turn of the century and the percentSCHWARTZ: Not by age. GARFINKEL: No, but percent of smokers continued to rise until the cohort born in the mid-1920s. JOHNFox (Ofjice of Population Censuses and Surveys, London, England): That cohort with the highest lung cancer riskis the one that fought in World War I and took up smoking at that time. The group of women taking up smoking 20 years later was associated with going to work in factories during World War I1 in our country. GARFINKEL: But did the cohort of people who were born, let’s say, in 1915 to 1920 have a higher percentage of people who were smoking than the birth cohort that went into World War I and were the first cohort that really started smoking heavily? Fox:It’s the duration of smoking as well as the proportion that are smoking that is important. DEVRA DAVIS (National Research Council, Washington, DC):Those born before the turn of the century experienced the greatest rate of lung cancer deaths, although they did not consume the greatest number of pack-years of cigarettes. One possible explanation can be derived fromreports on “Prevalence of Cigarette Smoking in the U.S., Estimates from the Current Population Survey.” There is almost a twofold difference in the percent of current smokers who are blue-collar versus white-collar in certain areas of the United States. This certainly suggests that anoccupationalfactor may explain thisexcessof lungcancerin the oldest cohort. If you look at the cohort of people born in 1895 in terms of the kinds of places they might have worked in, we have to consider that they might have had more per capita exposure as a cohort to dirtier work places, as well as having consumed fewer fresh fruits and vegetables year round. In addition, this cohort experienced the pandemic influenza that might have left them more vulnerable to subsequent initiation of oncogenes. There are multiple factors to be considered, but I think occupation is certainly one to be looked at very carefully in this group that shows a higher rate of lung cancer despite having fewer pack-years of exposure. HERBERTSEIDMAN (American Cancer Society, New York, NY): There was an enormous qualitative difference in cigarettes up until the early 1950s in terms of the kindsof cigarettes people smoked. We don’t even realize the kind of waning that took place since the 1950s. But those of us who worked in the field back in the 1950s know how different the kinds of cigarettes that developed gradually since the 1950sare. So if you’re talking about people who were born at the turn of the century, there is a revolution in terms of cigarettes and the kind of cigarettes that were smoked and in terms of the kind of accumulated damage. A. ENGLUND (Bygghulsan, Sweden):A comment with regard to occupational exposures here. We are following painters among other construction worker trades in
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Sweden. We have an excess lung cancer among the painters up to those who were born around the turn of the century, but not after. And this might fit into what Dr. Davis said. HANS HOFEMEISTER (Institutefor Social Medicineand Epidemiology, Berlin, F.R. G.): Did you observe also in the United States what we see in the Federal Republic-that smoking of the 1980s is not the same as in the 196Os? People who nowadays say I’m a non-smoker are very often people who smoke up to 10cigarettes. It has to d o with the social pressure growing over the last 20 years, and this creates a misclassification error you have to deal with. GARFINKEL: I can’t answer that question. The dataon percent smokers comes from the healthinterview surveys of the National Center for Health Statistics. As far as our own data is concerned, there wouldn’t be reason for them to hide it because it was a confidential questionnaire and they could put their answers into an envelope. There certainly are enormous changes. SCHWAR-IZ:We may have the answer in the U S . in a few years because the third national health and nutrition survey is going to be measuring urinary cotinines [a metabolite of cigarette smoke] as well as having the standardized questionnaire about how much you smoke. We’ll be able to take a look at the cotinine levels in the nonsmokers and perhaps get some information to answer what you’re saying in the U.S. HOFFMEISTER: We measure that, too, inournational healthsurvey, which is why we know that people are underreporting whether they smoke. Fox: We also get some data from longitudinal studies where people’s smoking history was recorded in 1958,1965,’and 1974. You can look at the individual level, at the extent to which they start reporting themselves as non-smokers as opposed to exsmokers. We can pick up that class of smoker.
Lung cancer is the leading cause of cancer incidence and death in the United States. The American Cancer Society estimated that there will be 157,000 new cases of lung cancer diagnosed in 1990 and 142,000 deaths.' Death rates in men have shown a remarkableincreasein the last 5Oyears paralleling arise in cigarette smoking20 years earlier. Age-adjustedlungcancerdeathratesinmenintheunited Statesgrew from 11per 100,000population in 1940 to 73 per 100,000 in 1982. Since then the rate has leveled off. In 1986,it was 74. The lung cancer rate in women started to rise in the early 1960s from 6 per 100,000 to 25 per 100,000in 1986 adjusted to the total U.S. population in 1970. Lung cancer rates in young men age 35-44 started to decline in the 1970s and in men age 45-54 in the early 1980s. There has been a leveling off of mortality rates in men aged 5 5 4 4 . It is only in the oldest age groups that a steady increase in rates has been observed through 1986 (FIG.1). These trends indicate that there should be a decrease in the overall lung cancer mortality rate in men by the early 1 9 9 0 ~Among .~ women the age-specific rates continue to increase, except for age group 35-44, where adecrease has beenseenstartingintheearly 1980s,andalevelingofratesinagegroup 45-54 (FIG.2). In addition to a decrease in mortality trends, the incidence of lung cancer has also declined. Studies of lung cancer incidence by the SEER Program of the National Cancer Institute reveal that the annual percent increasein men between 1975and 1979 was l.6%, but between 1982 and 1986, there was an annual percent decrease in incidence rate of 0.8% .3 The rate in whites decreased by 0.9% annually during this period but increased by 0.8% in blacks. Among women the annual rate of increase diminishedfrom6.3% inthe 1975-1979period to2.8% in 1982-1985. In black women however, there was no change in the annual rate of increase in the two periods, 8.4% and 8.57'0, respectively. Cigarette consumption per capita in persons age 18 and older measures total cigarette consumption divided by the estimated population and includes nonsmokers and exsmokers as well as smokers in the denominator. The index rose steadily from 1,085in 1925to 3,886 in 1952. Following publication of the smoking-health reports in the early 1950s, the index dropped 9% to 3,546 in 1954. It then continued to rise until 146
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1963 when it reached 4,345. With the publication of the first Surgeon General’s Report on smoking in 1964, the index dropped 4.5% to 4,194.It rose again to 4,287 in 1966. During 1969-1971, another drop of 5% accompanied the anti-smoking advertising on television. When these ads were removed the index climbed again to a high of 4,148in 1973. Since then in association with the growth of the nonsmoker movement and anti-smoking legislation restricting smokingin publicplaces, there has been a steady decIine to 2,936 in 1989,the lowest level since 1942.4 This decline is related to the leveling off of lung cancer mortality rates.
75+
65-74
55-81
ALL AGES
4544
3
w
FIGURE 1. Male lung cancerdeath rates, United States (19504951‘0 1984-1985). Standardized on the age distribution of the population of the United States, 1970.
Data on the prevalence of cigarette smoking have been collected by the National Health Survey of the National Center for Health Statistics every several years since 1965. The percent of men who smoked cigarettes decreased from 50.2% in 1965 to 31.8% in 1987.’ In women, cigarette smoking also decreased from 31.9% in 1965 to 26.8% in 1987(FIG.3). Cigarette smoking is more common in blacks than in whites. In 1987.32.9% of blacks and 28.5% of whites were current smokers, although whites smoke more cigarettes per day. The largest differences in smoking are seen between educational groups. There was little difference in 1965 in the percent of cigarette smokers between those with less than a high school education (36.5%) and college graduates (33.7%). However in 1987,35.7% of those with less than a high school education smoked while only 16.3% ofcollegegraduatessmoked,adropofmorethan 50%. Amonghighschoolgraduates,33.1% smokedcigarettesandin thosewithsome college education, 26.1Y0smoked. It is estimated that by the year 2000 if present
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65-74
75r 5564
4554 ALL AGES
35-44
* - ,------
trends continue that only 22% of the adult population will be smoking and that only 10% of collegegraduates will be cigarette smokers .6 This indicates that quit-smoking messages are reaching better educated groups to a greater extent than those with less education. Further evidenceof changesin smokingpattenscan be seen by comparing smoking distribution age-standardized to the population of U.S. women over age 35 in 1970in two American Cancer Society prospective epidemiologic studies of middle class volunteers in 1959 and 1982. The first, Cancer Prevention Study I (CPS I), included 1,078,000 persons enrolled in 25 states. The second, Cancer Prevention Study 11, included 1,200,000subjects in all 50 states. The subjects were basically the same type: mostly middle-class Americans ages 30 and older, enrolled by volunteers of the American Cancer Society. More than 98% of subjects enrolled in CPS I were traced (alive or dead) over a 12-year period. In CPS 11,subjects have been traced so far for 4 years (1982-1986). In CPS I in 1959,48.4% of men smoked cigarettes. In CPS IT, in 1982, the percent of smokers had dropped to 24.4%. Ex-cigarette smokers comprised 41.4% in CPS I1 and less than half that percentage (17.3%) in CPS I. Among women, more reported they had ever smoked in CPS I1 (43.6%) than in CPS I (32.8%), and a larger percentage were current smokers (27.2%) than in CPS IT (21.5%). Butthepercentex-cigarettesmokerswas22.1Y0in CPSIIand5.6% inCPS I, about four times as high. During the period of these two American Cancer Society studies, the relative risk of lung cancer in women smokers compared to nonsmokers increased dramatically. This is illustrated by the data in TABLE 1. Age-standardized rates are shown for three 4-year periods in CPS I and for one 4-year period (1982-1986) in CPS 11. The rate for
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nonsmoking females remained fairly constant over the 26-year period, about 12 per 100,OOO. However the lung cancer rate in cigarette smokers rose from 23.9 in 19601964, to 36.5 in 1965-1968, to 54.0 in 1969-1972, and to 130.4 in 1982-1986. The relativerisksforcigarettesmokersroseoverthat periodoftimefrom2.0, to2.9, to4.5, to 10.8.’ In men, the lung cancer rate in nonsmokers standardized to the U.S. population age 35 and over was about 15 per 100,OOO over the four periods, but the relative risks for cigarette smokers rose from about 9 in each of the three periods in the earlier study to 17.4 in CPS 11. The major reasons for the increase in relative risks in women are illustrated in TABLES 2 and 3. TABLE 2 shows the percent of women who reportedly smoked 20 or more cigarettedday in CPS I and CPS 11, by age group. In each age group, there was a far higher percentage of smokers who smoked 20 or more cigarettedday in CPS I1 than in CPS I; with an absolute average difference of 20.6%. Similarly, the average age began smoking for CPS I1 subjectsdecreased 3.3 years at age 4 5 4 9 compared to CPS I, and the difference was 10.1 years at age 65-69. Overall the age-adjusted differenceinage begansmokinginCPSIIwas7.2yearsyoungerthaninCPS I.9These differencesin exposure help to explain the large increases in relative risks in smoking women. In addition, a larger proportion of women in the third period of CPS I were smokers and smoked more heavily compared to women of the same attained ages in the first and second 4-year periods. Relative risks in CPS I1 also increased according to the number of cigarettes smokedlday. They rose from 5.5 to 1for those who smoked 1to 10cigarettedday; to 11.2for 11to 19cigarettedday; 14.2for20cigarettes/day;20.4 for 21 to30cigarettedday; and 22.0 for 31 or more cigarettedday. These relative risks are similar to those seen in men in CPS I. Since the early 1950s,American cigaretteshave undergone many changes,with the
so
-
40
..
s 30-
. . I -
-----FEMALES
20
-
10
-
n
I
I
I
I
I
I
I
I
I
I
I
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Age-Standardized Rates in Smokers and Nonsmokers and Relative Risks over Time, by Sex
TABLE I.
Cancer Prevention Study I
1960-1964
1965-1968
Cancer Prevention Study I1 ___ 1969-1972 1982-1986
Females Never smoked Cigarette smoker Relative risk
11.7 23.9 2.0
12.4 36.5 2.9
12.2 54.0 6.5
12.1 130.4 10.8
Males Never smoked Cigarette smoker Relative risk
14.6 137.0 9.4
16.6 154.0 9.3
16.7 160.6 9.6
15.4 267.9 17.4
Rates are standardized to the age distribution of the U.S. population, 1970.
introduction of filter-tip cigarettes in the mid-l950s, specially processed tobacco to reduce tar and nicotine, introduction of new brands, perforated cigarette paper, etc. The percent of plain-tipcigarettes has dropped to an estimated4% of the total market in 1989. Tar and nicotine levels have fallen steadily for the past 35 years. In 1982 according to data in CPS 11, cigarettes brands with less than 10 mg of tar comprised 25.1% ofcigarettebrandssmokedbyrnen,and33.1% ofthosesmoked bywomen. On theother hand,cigaretteswith 20or moremg tarweresmoked by 16.1%of males and only6.2% of females.’ In 1959,when data from CPS I were collected, more than 88% ofmen and78% ofwomensmokedcigaretteswith20ormoremgtar~andbrandswith less than 10 mg of tar made up less than 1%of the total market.” An analysis of data from CPS I has shown that persons smoking cigarettes with relatively low tar and nicotine had a reduction in lung cancer of about 25% compared to those smoking high tadnicotine cigarettes. This study matched subjectsin number of cigarettes smoked, age began smoking, and seven other variables to compare lung cancer mortality in high, medium, and low tadnicotine smokers. Smokers of “low” tar cigarettes smoked cigarettes with less than 17.6 mg tar; “high” tar included those w h o TABLE 2.
Percent of Smokers Smoking 20+ CigarettedDay Women
Age Group (Yo.)
Cancer Prevention Study I (Yo)
4549 50 -54 55-59 60-64 65-69 70--74 75+ Age-adjusted Difference
44.6 42.7 39.9 36.3 31.9 26.7 23.8
Cancer Prevention Study I1
Absolute Difference (Yo)
(1%)
63.2 62.4 61.0 58.4 53.1 47.1 45.1
18.6 19.7 21.1 22.1 21.2 20.4 21.3 20.6
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smoked cigarettes with 25.8 or more mg and “medium” tar were those in between. Therewasaconsistent dropin thelungcancerrate from high tomediumtolow in both males and females over two 4-month periods of time.” It should be recognized that what was called “low” tar in 1959 would be classified as “medium” tar in the 1980s. Another analysis from these data showed that smokers of “low” tar cigarettes who smoked 20 to 39 cigaretteslday had lung cancer rates 71% higher than smokers of “high” tar cigarettes who smoked less than 20 cigarettes a day.12 This analysis therefore showed that tar level was less important in lung cancer rates than the number of cigarettes smoked per day. In an analysis of the relative risk of lung cancer by tar content of cigarettesin CPS 11,it was also found that there was an increasing increment associated with increasing tar exposure in women, holding number of cigarettes and age began smoking ~ o n s t a n tThe . ~ relative risks of smoking cigarettes with tar yields 5,10,15, and 20mg compared to nonsmokers were 1.17,1.36,1.59, and 1.85, respectively.
TABLE 3
Average Age Began Cigarette Smoking Women
Age Group
Cancer Prevention Study I
Cancer Prevention Study 11
Absolute Difference
22.7 25.3 28.6 30.8 32.2 32.7 33.3
19.4 20.0 20.8 21.7 22.1 24.3 27.4
3.3 5.3 7.8 9.1 10.1 8.4 5.9
45-49
50-54 55-59 60-64
65-69 70-74 75+
Age-adjusted Difference
7.2
Previously, we found that lung cancer rates decrease when subjects stopped smoking. The rates were highest in those who quit less than one year before the study began. This group is weighted with sick people who quit because of disease. But rates start to decrease after 1year of cessation and by the time smokers have quit for 10 or more years, the lung cancer rate approaches that of persons who never smoked; for heavy smokers some risk remains.13 We found similar patterns in women who reported they quit smokingin CPS 11. Inwomen who had smoked21 ormorecigarettes/ day, rates were 21.2 times higher in current smokers thanin nonsmokers and 32.5 times higher in those who quit up to 2 years before the study began. The relative risks dropped to 20.3 for those who quit 3 to 5 years, 11.4 for those who quit 6 to 10 years, and 4.0 for those who quit 11or more years before the study began (FIG.4). As cigarette smoking is slowly being brought under control, another matter of great concern has risen. TBLE4 shows that while domesticconsumption has continued to decrease over the last eight years, total production of cigarettes has increased in the past four years. This is because of a 130% increase in exports over the past five years, from 56.5 billion to 130.0 billion in 1989. Exports now comprise 19% of total cigarette production. While our efforts to control smoking in the United States have been succeeding, tobacco companies are shifting their attention to overseas markets.
c
t01 4
21 or More Cigarettes a Day
@
FIGURE 4. Relative risks in ex-smokers, by number of years quit. Women, Cancer Prevention Study 11.
1-20 Cigarettes a Day
1.o
B
1.o
B
13.6
21.2
32.4
GARFINKEL & SILVERBERG: LUNG CANCER AND SMOKING TRENDS TABLE A
Year
1981 1982 1983 1986 1985 1986 1987 1988' 1989.
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Cigarette Production in the United States and Exports 1981-1989 Production (Billions)
736.5 694.2 667.0 668.8 665.3 658.0 689.6 694.5 685.0
Exports
Number (Billions)
%
82.6 73.6 60.7 56.5 58.9 64.3 100.2 118.5 130.0
11.2 10.6 9.1 8.4 8.9 9.8 14.5 17.1 19.0
Annual Change Domestic Consumption
+1.3% -0.9 -5.6 +0.7 -1.1 -1.7 -1.5 -2.2 -3.6
Data from Tobacco Situation and Outlook Report, US. Department of Agriculture, September 1989. *Preliminary estimate.
DISCUSSION Data from this study indicate that attempts to control cigarette smoking in the United States are succeeding and the efforts of researchers, public health educators, cancer control officials, physicians, lobbyists, etc. have all come together to have a visible impact on smoking rates and lung cancer mortality rates in men. Successwill take somewhat longer in women because of rapid rate of increase in smoking over the past several decades but some evidence of successin controlling smoking is apparent in women, especially younger and better educated women. Smoking prevalence has dropped by more than 50% in college graduates and it is in thisgroup wheresmokingcontrol methods have had their greatest success. Efforts now have to be concentrated on those with less than a high school education to persuade them not to smoke. There has been little change in the percent smokers in this group since 1965. A larger percentage of blacks smoke than whites, but they tend to smoke fewer cigarettes per day.I4 Yet blacks continue to have lung cancer rates about 40% higher than whites. This factor is worthy of further study to determine the reasons for this fact. Of major concern is the trend for more shipments of cigarettes overseas. Cigarettes shipped abroad do not come under the U.S. laws for labeling of tar and nicotine content and are, in general, higher in tar yields than cigarettes sold in the United States. Efforts by cancer control authorities and legislative activists are being extended to deal with this growing problem.
REFERENCES
1. SILVERBERG, E., C. S. BORING & T. S. SQUIRES. 1990.Cancer Statistics.1990.CA 40: 9-26. 2. DEVESA, S. S., W. J. BLOT& J. F. FRAUMENI, JR. 1989.Declining lung cancer rates among
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3.
4. 5. 6. 7.
8. 9. 10.
11.
12.
13. 14.
ANNALS NEW YORK ACADEMY OF SCIENCES young men and women in the United States: A cohort analysis. J. Natl. Cancer Inst. 81: 1568-1571 E. SONDIK & Office on Smoking and Health, Center for Chronic RIES,L. A,, B. R. EDWARDS, Disease Prevention and Health Promotion. 1989. Trends in lung cancer incidence, U.S. 1973-1986. Morbid. Mortal. Weekly Rep. 38: 505-513. U.S. Dept. of Agriculture, Economic Research Service. 1989. Tobacco Situation and Outlook, TS-208. Sept. 1989. U.S. PublicHealth Service. 1989. Reducing the Health Consequencesof Smoking: 25 Ycars of Progress. A Report of the Surgeon General. DHHS Publication No. (CDC) 89-8411. U.S. Dept. of Health and Human Services. Washington, D.C. E. J. HATZIANDREU & R. M. DAVIS.1989. Trends PIERCE,J. P., M. C. FIORE,T. E. NOVOTNY, in cigarette smoking in the United States: Projections to the year 2000. JAMA 261:6165. GARFINKEL, L. 1985. Selection, follow-up and analysis in the American Cancer Society’s prospective studies. Natl. Cancer Inst. Monog. 67: 49-52, STELLMAN, S. D. & L. GARFINKEL. 1986. Smoking habits and tar levels in a new American Cancer Society prospective study of 1.2 million men and women. J. Natl. Cancer Inst. 76c 1057-1063. GARFINKEL, L. & S. D. STELLMAN. 1988. Smoking and lung cancer in women: Findings in a prospective study. Cancer Res. 48:69514955. E. C. & L. GARFINKEL. 1961.Smoking habits of men and women. J. Natl. Cancer HAMMOND, Inst. 27: 617-631. HAMMOND, E. C., L. GARFINKEL, H. SEIDMAN & E. A. LEW.1976. “Tar” and nicotine content of cigarette smoke in relation to death rates. Environ. Res. 12:263-274. E. C., L. GARFINKEL, H. SEIDMAN & E. A. LEW.1977. Some recent findings HAMMONU, concerning cigarette smoking. In: The Origins of Human Cancer. H. H. Hiatt, J. D. Watson & J. A. Winsten, Eds. A: 101-112. Cold Springs Harbor Laboratory. New York. HAMMOND, E. C. 1966. Smoking in relation to the death rates of onc million men and women. Natl. Cancer Inst. Monogr. Sk 127-204. SCHOENBORN, C. A. & B. H. COHEN.1986. Trends in smoking, alcohol consumption and other health practices among U.S. adults, 1977 and 1983. Advance Data from Vital and Health Statistics, No. 118. DHHS Publication No. (PHS) 86-1250. National Center for Health Statistics. U.S. Public Health Service. Washington, DC.
DISCUSSION
ANTHONK MAZZOCCHI (Oil, Atomic, and Chemical Workers Union, AFL-CIO): I would hope that investigators in the future will look into occupational factors more carefully. It may be that less educated people are doing more stressful work and it’s much more difficult to quit. Also, the trend in the United States of increased daily hours of work may increase stress and smoking. More people work 16 hours straight now than ever before, and I would hope that you begin to factor that trend into future studies. LAWRENCE GARFINKEL: One of the things we’re going to do is find o u t whether 01 not people work swing shifts and how much stress they are under at work. Then we’ll take that into consideration when we get to that analysis. JOELSCHWARTZ ( U S . Environmental Protection Agency, Washington, D C ) :Your second figure shows the time trends by different age groups. Dr. Davis and I noted a coupleofyearsago that ifyoulookat where theinflection point started tocurvedown in the age 35 to 44cohort and then you look at the inflection point where it’s beginning
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tocurvedownin theage45 to54cohort, thedeclineisshowing up 10yearslaterin the 10-year older group. This goes back to a previous comment about cohort effect. GARFINKEL: That ties in very nicely with the percent smokers by the way. MARVINS~DERM AN (NationalResearch Council, Washington,DC):I share your pleasure and delight at these rates decreasing and at thenumber of cigarettessmoked decreasing. There are two other things I would like to see. Cigarettes smoked these days contain less tobacco than they did in the past. When I first started looking at cigarettes30yearsagotheymade230cigarettesto thepoundof tobacco. Inthe United States, they are now making 400 cigarettes to the pound of tobacco. Slim cigarettes really are slim. If you could put that in with your cigarette consumption, we ought to show much greater decreases. But what concerns me, having mentioned this, are two things. I hope you have enough data on blacks to look at this. Black males have 40 to 50% higher lung cancer rates than white males. The proportion of black smokers is roughly 5% higher than white smokers, yet the amount blacks smoke is less on the average, substantially less. The age of starting to smoke among the blacks is older than among the whites. Yet, there is this 40 to 50% increase in lung cancer rates. The rates for black women and white women are almost identical and black women smoke 70 to 75% as much as white women. I had hoped that your data would be enough to elucidate these differences. What else is going on? I realize yours is a middle class population and not a working class population and more suburban than central city urban. Let me add some comments concerning American Cancer Society (ACS) nonsmokers lung cancer rates. These rates do not seem to me to be applicable to all of the U.S., mostly because the ACS sample is unrepresentative. Because of changes in the tar and tobacco content of cigarettes since the 1960s, the risk of lung cancer per cigarettesmokedshould bedeclining. The ACSshowsthe risk asincreasing. The CPS I1 sample is more white, more white collar, and more suburban than the U S. population. Since lung cancer rates are higher among blacks, blue collar (industrial) workers, and central city (higher urban) dwellers, the rates for non-smokers as reported by CPS I1should be biased downward, and lower than the rates would be for a representative sample. Because cigarettes since 1960 have contained less tar, tobacco, and nicotine per cigarette, it is reasonable to conclude that the toxic responses (i.e., lung cancer) per cigarette would decline over time. The Hammond-Horn data and the Dorn (American veterans) data both showed that the relative risk (RR) for lung cancer per cigarette smoked was loosely approximated by the formula RR = 1 + 0.52d. where d is the number of cigarettes smoked per day. The most recent CPS II data would be better fit by the equation RR = + 0.8d, which indicates about 60% increase in “potency” (for producing lung cancer) per cigarette (i.e.,0.8/0.5 = 1.6). In addition to the lower tobacco content and the yield of tar per cigarette, there has been a very substantial switch to filter cigarettes, which, according to early reports (Wynder and Bross, for example) reduced the toxicity per cigarette.
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If the non-smoker lung cancer rates had been higher than reported by CPS I1 (i.e.. increasedfromCPS1 to CPSII) then the reportedrelative riskper cigarettewould not have increased, and might, in fact have declined, as the external evidence would suggest should have happened. What has happened instead is that the CPS I1 data imply that with lower tar filter cigarettes and fewer persons smoking cigarettes, the smoking attributable fraction (SAF) of lung cancers has increased:
25 Years Ago
5 to 10 Years Ago
If R R = 1 + .5d
1 + .8d 25
20
d Proportion smoking (p) SAP
.50 - .60 .83 .86
.35 - .45 ,875 .90
w 1) ”Excluding contributions by exsmokers, SAF = 1 1)
+m-
Thusit would have to be argued that withreducedsmoking and withless hazardous (lower tar, lower tobacc0,filtered) cigarettes, the proportion of lung cancer attributable to smoking has increased at the same time that total rates have decreased or remained stable. However, C. C .Brown and L. G. Kessler argue in a recent paper (J. Nutt. Cancer Znst. 1988,80:43-51) “...recent trends in lung cancer are unlikely to be affected by changes in cigarette composition and consumption in the near term...”. A more reasonable conclusion is that the ACS relative risks are too high, in part because ACS has underestimated the non-smoking related lung cancers, which have gone up in the interval between CPS I and CPS 11. GARFINKEI.: I don’t know if we have enough blacks to look at mortality rates without following them for a longer period of time. We have about 50,000 blacks in the study which, you know, sounds like a lot. But when you’re looking at mortality rates for a specific disease, it may not be sufficient. The other thing that I think you should be aware of is that the blacks in our sample population are middle class blacks. There are very few of the working class blacks. So I don’t know if a thorough analysis of our data will ever elucidate the effects of smoking on working class blacks. NO RE KoHLMEIER(znstirUfe~oeforSOciaIMedicineund Epidemiology,Berlin, l?R. G.): There are risk groups that we have to watch closely. I think one of them might also be the heavy smokers. In Germany, the picture may be very different than in the United States. We just did an analysis of the structural trends. Although we have a bit of a reduction in smoking, it is not comparable with the United States. Those people who smoke a lot are smoking more. That means not only in terms of t h e number of cigarettes, but in terms of the amount of exposure they’re getting to nicotine, tar, and other substances. So if you look at these special groups of heavy smokers, do you see the same trend in the United States as we’re seeing in Germany? The second issue is people with college degrees and smoking. Those are populations that have changedradically,haven’t they? When you started looking, there were fewer people who went to college. So the result is actually much more positive because more of the population is getting a college degree and more of them are not smoking. There is something dynamic going on there. I think it’s important to point out that if you’re talking about cigarette GARFINKEL:
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smokers over a long period of time, cigarette smokers in recent years contain a much heavier portion of heavy smokers because it’s the light smokers who have quit. The people who continue are heavier smokers. SCHWARTZ: In some of the SYSTAT graphs we produced you see a very strong cohort effect in terms of lung cancer in the older age groups. And, in fact, the cohort with the highest mortality rate at any given age is not the cohort that has the highest rate of smoking. It’s the cohort that was born around 1895. You can see this nice little diagonal ridge marching across those three-dimensional plots. GARFINKEL: Well, this may differ in different countries. But in the United States whenwedidour studyin 1959thehighestpercentageofsmokerswerethosewhowere born just before the turn of the century and the percentSCHWARTZ: Not by age. GARFINKEL: No, but percent of smokers continued to rise until the cohort born in the mid-1920s. JOHNFox (Ofjice of Population Censuses and Surveys, London, England): That cohort with the highest lung cancer riskis the one that fought in World War I and took up smoking at that time. The group of women taking up smoking 20 years later was associated with going to work in factories during World War I1 in our country. GARFINKEL: But did the cohort of people who were born, let’s say, in 1915 to 1920 have a higher percentage of people who were smoking than the birth cohort that went into World War I and were the first cohort that really started smoking heavily? Fox:It’s the duration of smoking as well as the proportion that are smoking that is important. DEVRA DAVIS (National Research Council, Washington, DC):Those born before the turn of the century experienced the greatest rate of lung cancer deaths, although they did not consume the greatest number of pack-years of cigarettes. One possible explanation can be derived fromreports on “Prevalence of Cigarette Smoking in the U.S., Estimates from the Current Population Survey.” There is almost a twofold difference in the percent of current smokers who are blue-collar versus white-collar in certain areas of the United States. This certainly suggests that anoccupationalfactor may explain thisexcessof lungcancerin the oldest cohort. If you look at the cohort of people born in 1895 in terms of the kinds of places they might have worked in, we have to consider that they might have had more per capita exposure as a cohort to dirtier work places, as well as having consumed fewer fresh fruits and vegetables year round. In addition, this cohort experienced the pandemic influenza that might have left them more vulnerable to subsequent initiation of oncogenes. There are multiple factors to be considered, but I think occupation is certainly one to be looked at very carefully in this group that shows a higher rate of lung cancer despite having fewer pack-years of exposure. HERBERTSEIDMAN (American Cancer Society, New York, NY): There was an enormous qualitative difference in cigarettes up until the early 1950s in terms of the kindsof cigarettes people smoked. We don’t even realize the kind of waning that took place since the 1950s. But those of us who worked in the field back in the 1950s know how different the kinds of cigarettes that developed gradually since the 1950sare. So if you’re talking about people who were born at the turn of the century, there is a revolution in terms of cigarettes and the kind of cigarettes that were smoked and in terms of the kind of accumulated damage. A. ENGLUND (Bygghulsan, Sweden):A comment with regard to occupational exposures here. We are following painters among other construction worker trades in
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Sweden. We have an excess lung cancer among the painters up to those who were born around the turn of the century, but not after. And this might fit into what Dr. Davis said. HANS HOFEMEISTER (Institutefor Social Medicineand Epidemiology, Berlin, F.R. G.): Did you observe also in the United States what we see in the Federal Republic-that smoking of the 1980s is not the same as in the 196Os? People who nowadays say I’m a non-smoker are very often people who smoke up to 10cigarettes. It has to d o with the social pressure growing over the last 20 years, and this creates a misclassification error you have to deal with. GARFINKEL: I can’t answer that question. The dataon percent smokers comes from the healthinterview surveys of the National Center for Health Statistics. As far as our own data is concerned, there wouldn’t be reason for them to hide it because it was a confidential questionnaire and they could put their answers into an envelope. There certainly are enormous changes. SCHWAR-IZ:We may have the answer in the U S . in a few years because the third national health and nutrition survey is going to be measuring urinary cotinines [a metabolite of cigarette smoke] as well as having the standardized questionnaire about how much you smoke. We’ll be able to take a look at the cotinine levels in the nonsmokers and perhaps get some information to answer what you’re saying in the U.S. HOFFMEISTER: We measure that, too, inournational healthsurvey, which is why we know that people are underreporting whether they smoke. Fox: We also get some data from longitudinal studies where people’s smoking history was recorded in 1958,1965,’and 1974. You can look at the individual level, at the extent to which they start reporting themselves as non-smokers as opposed to exsmokers. We can pick up that class of smoker.
