Changes associated with The Framingham Study
quitting
cigarette
smoking:
Tavia Gordon William B. Kannel, M.D. Thomas R. Dawber, M.D. Daniel McGee, M.S. Washington, DC, and Boston, Mass.
Since 1948, when the Framingham Study began, there has been a substantial change in cigarette smoking habits in the United States. One of its features-perhaps the most striking one-has been the substantial number of middle-aged men who have quit cigarette smoking.‘, * Presumably this has led to changes in medically related characteristics and in disease. The Framingham Study, which has had a general population under continuous observation during this period, provides an opportunity to assess the changes that have occurred.
The Framingham Study cohort when it first came under observation was 29 to 62 years old. The initial study population came from a sample of adults resident in the town of Framingham, Mass., and consisted of 5,209 men and women. They received a thorough standardized cardiovascular examination at entry which also elicited a large amount of information about their habits, their physical characteristics, their blood chemistry, and the like. Similar examinations were repeated every 2 years. This was supplemented by information on cardiovascular illness and death obtained from hospitals and other extra-clinic sources.3 From the Biometrics Research Branch, National Heart and Lung Institute, National Institutes of Health, Department of Health, Education and Welfare (Ms. Gordon and Dr. McGee); the Framingham Heart Disease Study, National Heart and Lung Institute, National Institutes of Health, Department of Health, Education, and Welfare, Washington, D.C. (Dr. Kannel); and Boston University Medical School, Boston, Maea. (Dr. Dawber). Received
for publication
Aug.
15, 1974.
Reprint requests to: Tavia Gordon, Supervisory Statistician, tries Research Branch, National Heart and Lung Institute, Institutes of Health, Bethesda, Md. 20014.
322
BiomeNational
Details with respect to laboratory methods and clinical criteria are available elsewhere.4 Histories of cigarette smoking were obtained on every examination except Exam. 6; however, information from the first three examinations was coded to represent usage at Exam. 1, leaving Exams. 2 and 3 uncoded. (More than half of those coded to Exam. 1 actually derived from Exam. 1, the bulk of the remainder from Exam. 2.) Unless otherwise specified, “smoking” means smoking cigarettes. In previous reports from the Framingham Study, “quitting” was defined retrospectively by a history of previous smoking habits obtained at entry to the study. Some data in that form are presented in this report but this is supplemented for the first time by information on people who were smoking when they first came under observation and who, while they were still under observation, quit smoking. Weight, blood pressure, vital capacity, drinking habits, and so on, were measured while they were still smoking and again after they quit. What happened concurrently to people smoking at entry who continued to smoke is also available from the routine re-examination of the cohort. Changes in characteristics are examined in two ways: (1) short-term changes occurring in the interval between the last examination while smoking and the following examination, that is, the first examination after quitting, and (2) longterm changes (between Exams. 4 and 10) for persons smoking at entry but quitting by Exam. 4. Age-specific means for the characteristics were calculated for the age groups 35 to 44, 45 to 54, and 55 years and over (age at Exam. 4). These means provided the basis for age-adjustment. Comparisons are made between those who quit and those continuing to smoke, with those not
September,
1975, Vol. 90, No. 3, pp, 322-328
Quitting
smoking:
Thp Frrrmingham
Stu&
I. Per cent smoking cigarettes by age and sex: Framingham Study, Exams. 1 and lO*
Table
All ages
61.0
37.1
40.2
31.0
29-33 34-37 38-41 42-45 46-49 50-53 54-57 58-62
62.8 71.5 67.2 58.0 56.1 58.9 43.6 48.3
43.8 48.0 45.2 32.4 29.9 32.1 18.8 18.6
51.1 56.6 48.8 38.0 28.1 28.7 23.4 15.0
43.0 48.5 37.2 29.8 20.0 18.7 12.4 6.0
ki y 20 i 1
- Men --Women
IO 1 01
*Persons must take both Exams. 1 and 10 to be included. Age is at Exam. 1 and defines age-specific cohorts followed for 18 years.
’
’
I
I
I
I
i
I
I
I
I
2
3 ‘53‘56
4 ‘54‘50
5 ’56s ‘60
6 ‘58‘62
7
0
9
IO
‘60‘64
‘62‘66
‘64‘68
l948-
‘53
I I. Per cent of men and women not smoking cigarettes after 18 years by original smoking status: Framingham Study*
‘?A-
‘54
‘66‘70
Exam
Table
Fig. 1. Per cent of men examination: Framingham
and women smoking cigarettes Study, Exams. 1 to 10.
Stop@
on
Smokbng
by foflorlng exam -
0 l-10 11-19 20 21-39 40+ *Includes
599 165 89 393 188 98
95.7 58.2 41.6 38.2 38.3 35.7
only persons who took Exam.
1226 417 139 208 41 18
97.0 39.3 18.0 13.5 14.6 5.6
10. -25
smoking at entry serving as a reference group. Statements of statistical significance are made at a 5 per cent level. It is, of course, difficult to decide when a person has quit smoking cigarettes and the criteria followed early in the study are not well defined. On later examinations, a person who had smoked for more than a year in the last 2 years was classified as a smoker, whatever his immediate smoking behavior. The relapse rate for those classified as quitting is low enough throughout the study to suggest that the criteria for quitting must always have excluded persons who were only beginning to try. Only about 20 per cent of the men who reported that they had quit at entry ever reported smoking cigarettes again, and nearly half of those who resumed smoking
American
Heart
Journal
-I5
-5 +5 +15 WEIGHT CHANOE On pcwdrl
+25
+35
+40
2. Weight change according to change in smoking habits in men under 65 years of age smoking cigarettes on examination: Framingham Study, Exams. 1 to 10. Fig.
smoked very little or only intermittently resumption.
after
Results Changes in smoking habits. Trends from 1948 to 1953, when the initial examination was performed, to the tenth biennial examination in 1966 to 1970 are shown for men and women in Fig. 1. Only persons taking both Exams. 1 and 10 are included. At entry 61 per cent of the men and 40 per cent of the women smoked cigarettes. Eighteen years later only 37 per cent of the men and 31 per cent of the women were still smoking.
323
Gordon
Table
et al.
III. Mean values of specified characteristics at entry by smoking status: Framingham Study* No. of cigarettes/day None Sex, characteristic
Men,
number
Age-adjusted
Women,
number
values
Never
Quit
Cigar, pipe
Total
803
277
215
311
1,498
138.1 87.8 381.2 17.4 172.9 5.3 224.0 83.4
138.4 87.5 382.4 10.0 173.4 5.2 222.0 84.1
137.8 87.4 382.4 20.7 171.7 5.3 230.5 82.7
138.0 88.3 379.4 21.7 173.2 5.2 221.3 83.2
1,634
1543
for the age groups
29-44,
45-54,
138.5 85.6 255.8 4.4 143.7 4.0 227.5 82.8 and
55-62
were
138.7 85.6 254.7 4.1 144.0 4.0 227.6 83.0 weighted
Decreases were fairly continuous during those 18 years, beginning as early as the second examination (1951 to 1954), with an accelerated rate of decline, especially apparent in men, beginning after Exam. 7 (1960 to 1964). Additional details of these changes are available elsewhere.” Table I compares the per cent smoking at Exam. 1 with the per cent smoking at Exam. 10. Decreases were observed for all age groups. By Exam. 10 men had dropped to about the Exam. 1 smoking levels of women. Women smokers were more persistent in retaining their original smoking habits, although even for them small decreaseswere observed for every age group. The more a person smoked at entry the less likely he was to be a nonsmoker 18 years later (Table II). Quit rates for women were lower than those for men in all smoking categories. So few Framingham women quit since the study began that their experience is not analyzed in this report. Characteristics by smoking habit at entry. At entry body weight varied according to smoking habit. For men the difference between cigarette smokers and nonsmokers was 8 pounds (Table
324
l-10
11-19
20
21-39
40+
254
139
608
314
183
91
136.1 85.4 371.4 27.5 164.7 5.0 228.5 82.4
138.1 86.8 372.4 23.4 165.0 5.2 225.4 81.6
133.9 83.5 372.3 18.3 160.5 4.9 226.1 82.9
134.8 84.9 373.7 24.1 162.9 5.0 228.6 82.5
136.8 85.6 372.5 30.7 166.4 5.1 229.6 81.6
138.1 86.7 359.6 45.8 170.2 5.2 232.5 83.8
1.174
580
182
313
75
24
133.9 83.5 264.0 8.4 139.4 4.0 226.9 82.0
134.4 82.3 263.6 11.0 133.2 4.0 235.4 81.2
134.7 83.4 262.2 11.6 138.1 4.0 234.1 79.9
131.5 83.7 260.6 17.7 139.2 4.5 240.8 80.9
154.9 92.5 244.8 19.6 144.4 4.3 209.8 77.4
mean values:
Systolic blood pressure (mm. Hg) Diastolic blood pressure (mm. Hg) Vital capacity (L.) Alcohol (oz./ma.) Weight (lb.) Uric acid (mg./lOO ml.) Serum cholesterol (mg./lOO ml.) Blood sugar (mg./lOO ml.) *Mean
Total
mean values:
Systolic blood pressure (mm. Hg) Diastolic blood pressure (mm. Hg) Vital capacity (L.) Alcohol (oz./ma.) Weight (lb.) Uric acid (mg./lOO ml.) Serum cholesterol (mg./lOO ml.) Blood sugar (mg./lOo ml.)
Age-adjclsted
Cigarette smoker
135.6 84.6 274.9 9.2 139.1 4.1 226.2 79.8 12122,
7122,
134.5 83.5 262.9 10.5 138.1 4.0 230.6 81.2 and
3122,
respectively,
to yield
age-adjusted
mean
values.
III). Nonsmokers include those who never smoked, those who had quit, and those smoking cigars or pipes. There is little difference in their weights. Smokers’ weights varied with the amount smoked, but no matter how many cigarettes were smoked per day, the average weight was less than that for nonsmokers. The leanest smokers were those smoking 11 to 19 cigarettes per day. Men smoking more than this weighed more, their weight being greater the more they smoked. Men smoking 40 or more cigarettes per day weighed nearly as much as nonsmokers. Data for women were very similar. Thus, while weight is clearly related to the fact of smoking and to the amount smoked, the association is nonlinear and therefore cannot be satisfactorily represented by a correlation coefficient or linear regression. In addition to weight only two other of the characteristics listed in Table III were found to differ between smokers and nonsmokers at entry-alcohol and vital capacity. Persons who never smoked used little alcohol, on the average, while men or women who smoked used more, the amount being greater the more cigarettes smoked. Vital capacity is lower among men smoking ciga-
September,
1975, Vol. 90, No. 3
Quitting
smoking:
Thr Frammgham
Studv
IV. Age-adjusted mean levels at entry of selected characteristics for cigarette smokers according to subsequent smoking history: Men, Framingham Study
Table
Mean Men smoking cigarettes/day
Characteristic Systolic blood pressure (mm. Hd Diastolic blood pressure (mm. Hg) Vital capacity (L.) Alcohol (oz./ma.) Weight (lb.) Uric acid (mg./lOQ ml.) Serum cholesterol (mg./ 100 ml.) Blood glucose (mg./lOO ml.) *Age-adjusted
means
are unweighted
l-10 at entry
Heart
Journal
at entry* Men smoking 20 cigarettes/day at en tT
Still smoking at Exam. 4
Not smoking at Exam. 4
Still smoking at Exam. 4
Not smoking ot Exam. 4
137.3
136.0
134.5
131.1
86.7
85.3
84.8
83.2
367.8 23.4 164.1 5.2 223.6
382.3 21.8 168.2 5.2 225.5
375.5 24.5 162.8 5.0 228.8
382.2 23.6 162.8 5.0 228.8
79.4
93.6
79.1
87.9
averages
of the
age-specific
means.
rettes than those not smoking. For women the difference in vital capacity is in the opposite direction. Both contrasts are statistically significant, if relatively small. Persons of either sex smoking 40 or more cigarettes per day have distinctly lower vital capacities than others, but few women smoked 40 or more cigarettes per day. Characteristics of men who later quit. Since so few women have quit smoking all the subsequent analysis is confined to men. It seemslikely that men who quit smoking are different from persons who continue smoking. What is not clear is whether the differences are such as to influence subsequent morbidity and mortality rates. Without a clinical trial involving randomization and the other usual safeguards of such trials it is impossible to conclusively resolve such an issue but it is possible to look at some relevant characteristics of smokers measured while they were still smoking and compare those smokers who subsequently quit with those who continued smoking (Table IV). Data are presented separately for men smoking one to 10 cigarettes per day and “exactly” 20 cigarettes per day at entry. These two groups account for the bulk of those subsequently quitting. When these comparisons are made only minor differences, in general, are noted. There were only trivial and not statistically significant differences between those who later quit and those who
American
level
continued smoking with respect to their entry levels for blood pressure, vital capacity, alcohol consumption, weight, uric acid, or serum cholesterol. There was one exception: Men who quit had a higher average blood glucose level before quitting than men who continued smoking. Most of the difference is accounted for by an excess number of diabetic subjects among smokers who quit smoking. This presumably indicates that ill health (in this instance, diabetes) is an incentive to stop smoking. Short-term changes after quitting. Under observation men under age 65 who quit smoking gained a small amount of weight immediately (3.8 pounds on the average) (Table V). If they were still not smoking at the next examination their weight remained fixed at the new level. (For this subgroup off cigarettes for two full examinations the average initial gain was 5.1 pounds followed by a trivial gain-O.3 pounds-in the next 2 years.) While there is a slight tendency toward weight gain (about half a pound) in men whose smoking habits remained unchanged from one examination to the next, this was, of course, significantly less than the weight increase for those who quit. Persons who resumed smoking lost about a pound after resumption. Illness, particularly the onset of clinical cardiovascular disease, may be a powerful incentive to stopping smoking and is also associated with weight changes. The average weight gain
325
Gordon
et al.
V. Changes in weight, systolic blood pressure, and serum cholesterol in smoking habits: Framingham Study, men under age 65 years*
Table
levels by change
Average change in characteristic Change in smoking habits from one exam. to next
No.?
Weight @.A
Serum cholesterol (mg./lOO ml.)
Smoking to nonsmoking Continued smoking
544 4,078
3.8 0.3
(2.3) (0.1)
1.6 0.7
0.2 -0.2
Nonsmoking to smoking Continued not smoking
246 3,120
-0.9 0.5
(-0.8) (0.1)
0.6 0.7
1.9 0.3
*Smoking histories are available at Exams. 1, 4, 5, 7, 8, 9, and 10. Only reports of current measurements on the same pair of examinations. The intervals are those between exams. tNumber of changes, not number of persons. $Parenthetical entries are for men free of cardiovascular disease on the first examination
after quitting is less if such persons are omitted, but the difference is trivial. The average difference in weight change between those who quit and those who continued smoking cigarettes is not accounted for by a few men with very large weight gains but arises from the fact that proportionately fewer among those who quit lost weight and more among them gained at least 10 pounds (Fig. 2). One would anticipate that the greater weight increase in smokers who quit relative to those continuing to smoke would be associated with relatively greater increases in blood pressure and serum cholesterol. In fact the difference in trends for these two characteristics is trivial and not statistically significant (Table V). Table VI considers changes for a number of characteristics in men who were smoking either one to 10 or 20 cigarettes per day at Exam. 1. These men are divided into two groups, according as they were or were not still smoking at Exam. 4. Short-term changes for those who quit are contrasted with short-term changes for those still smoking at Exam. 4 in the upper half of the table. These changes are compared with concurrent changes for those who continued to smoke. Both groups may be compared with those men who were not smoking at entry. For two characteristics-weight and vital capacity-men who quit smoking by Exam. 4 had statistically significant differences in trends from men still smoking at Exam. 4. The weight increase from Exams. 1 to 4 was greater for men who quit than for men who continued smoking, the difference being statistically significant for men smoking 20 cigarettes per day at entry.
326
Systolic blood pressure (mm. Hg)
smoking practices are considered, with smoking histories.
and
are compared
with
considered.
Men smoking 20 cigarettes per day who quit also had a statistically significant and substantially greater decrease in vital capacity between Exams. 1 and 4 than did those still smoking. This presumably implies that respiratory distress was one of the motives for quitting. Significant differences in short-term trends for those quitting and those continuing to smoke were not evident for alcohol consumption, uric acid, serum cholesterol, or blood sugar. Long-term changes after quitting. Long-term changes after quitting are shown for the 12 years between Exams. 4 and 10 in the lower half of Table VI. These may be contrasted with the initial short-term changes already discussed. There was a greater long-term decline in vital capacity for those who continued smoking than for those smoking the same amount who quit. For men smoking 20 cigarettes per day at entry the difference in trends was statistically significant. The long-term vital capacity trends of those who quit approached the concurrent experience of men who were not smoking at entry. Men who continued smoking had a greater long-term drop in serum cholesterol levels than those who quit but this difference was not statistically significant. Men who continued to smoke also had a slightly smaller long-term rise in blood pressure but, again, the difference was not statistically significant. After the initial weight changes, the long-term changes in weight for men who quit and men who continued to smoke cannot be distinguished. In brief, the only statistically significant difference in long-term trends among the variables considered is the greater drop in vital capacity for
September,
1975, Vol. 90, No. 3
Quitting
smoking:
‘The F’rrrrvinghnm
Study
VI. Change in smoking habits in men between Exams. 1 and 4 and concurrent and subsequent changes in certain other characteristics: Framingham Study ___~-.____
Table
f-10 cigarettes/day Characteristic Increase from Exams. 1 to 4: Systolic blood pressure (mm. Hg) Diastolic blood pressure (mm. Hg) Vital capacity (L.) Alcohol (oz./ma.) Weight (lb.) Uric acid (mg./lOO ml.) Serum cholesterol (mg./lOO ml.)$ Blood glucose (mg./lOO ml.)
Increase from Exams. 4 to 10: Systolic blood pressure (mm. Hg) Diastolic blood pressure (mm. Hg) Vital capacity (L.) Alcohol (oz./ml.)l( Weight (lb.) Uric acid (mg./lOO ml.) Serum cholesterol (mg./lOO ml.) Blood glucose (mg./lOO ml.)7
Not smoking at entry*
Quit at Exam. 4
-9.42
-0.22 3.43
-0.20
0.21
-2
(564)
(43) 10.12
7.66 -1.74
-1.72
-41.16 1.92
-40.47 3.27
-1.50 N.A. -7.47
10.39
*Adjusted to the age-distribution of men smoking l-10 cigarettes who quit and tAdjusted to the age-distribution of men smoking the same amount who quit. SParenthetical entries are the number of men in each group. §Exams. I and 4. IIExams. 4 and 7. llExams. 4 and 9.
While there is a considerable literature on the characteristics of men according to their smoking histories, there is very little information on what happened to men who quit smoking while under observation. Presumably such information is available in the files of various prospective studies but the subject seems to have excited little analytical interest. An exception is the Normative Aging Study which has recently published data on subjects measured 5 years apart. When the data for 214 continuing cigarette smokers are contrasted with data for 104 quitters the difference in weight gain was 4.2 poundsfi This is very similar to the Framingham findings. Findings with respect to blood pressure changes, however, differed somewhat.’ The Normative Aging Study reported continuing smokers had on the average no change in systolic blood pressure in 5 years but men who
American
Heart
Journal
Exam.
10.82 1.25 2.70 -0.06 7.53 1.97
(105) 7.57
139)
(348) 6.83 -0.92
-17.78 5.19 took
-1.88
6.43 x.54
N.A.
2.83
7.78 -0.29
(464) -1.79
12.18 0.77
7.57 1.20
-9.32
who
-0.16 -21.48 2.79
-0.07 -45.11
3.14 N.A.
(58) cl.97
-2.63
-0.20
5.32 70
20 cigar&es/dczy nt entry ..____~.-..~ ~. .-.. - - . ..._Quit at 1 Still smoking Exam. 4 ( at Exam. 4t I
-11.64 2.37 1.36
-0.31
6.38
Discussion
(152) -3.08
-18.63
2.07 2.53
men smoking 20 cigarettes per day at entry who continued to smoke.
Still smoking at Exam. 41
(51) -4.98 -3.04
(714)-J -4.00 -2.88
at entry
9.26 -0.79 -41.76 3.88 0.03 N.A. -5.48 2.16
-55.88 4.21 0.19
N.A. -12.27 7.66
4 (or IO).
quit had slightly higher systolic levels after quitting (3.6 mm. Hg). While this is a trivial difference and is probably of marginal statistical significance, it was noted that there was a greater blood pressure gain in each weight group among quitters than those continuing to smoke. The comparable data for Framingham would be those given in Table V for changes between Exams. 1 and 4. These show no difference in blood pressure trends for those who continued to smoke and those who quit despite a greater weight increase in those who quit. Unfortunately, strict comparability cannot be achieved, since the Normative Aging Study did not include men if their initial blood pressure was greater than l40/ 90 whereas there were no blood pressure exclusions in the Framingham Study. What is most striking in the Framingham data is how little difference there is between those who quit and those who continued smoking, either in their characteristics while still smoking or with respect to changes in these characteristics after stopping. Of the characteristics examined only
327
Gordon
et al.
two stand out-weight and vital capacity. A slightly greater short-term weight change and a smaller long-term decline in vital capacity among those who quit than among those who continued smoking were the chief findings. Only for men smoking more than 10 cigarettes per day were these differences statistically significant. No significant changes in blood pressure or serum cholesterol levels were found to be associated with quitting cigarette smoking. Information with respect to women smokers and with respect to men smoking more than a pack a day was too scanty for analysis, and it is conceivable that the effect of quitting is different in these groups than in the groups available for analysis. Men smoking a pack or less a day constitute the bulk of those who quit cigarette smoking and are consequently the group of major public health interest. In this group the impact of quitting on the major cardiovascular risk factors appears to be trivial so that the cardiovascular advantage of quitting cigarette smoking should be straightforward. Summary
During the first 18 years of the Framingham Study there was a substantial decrease (39 per cent) in the number of men smoking cigarettes and a moderate decrease (22 per cent) in the number of women smoking cigarettes. Except for a greater tendency of diabetic patients to quit smoking, there were no significant differences at
328
baseline between smokers who quit and smokers who continued smoking. After quitting there was a short-term rise in weight for men. This rise led only to trivial changes in blood pressure and serum cholesterol levels. There was a beneficial impact on long-term vital capacity trends from quitting smoking.
REFERENCES
1. Ahmed, P. I., and Gleeson, G. A.: Changes in cigarette smoking habits between 1955 and 1966, PHS Pub. No. 1000, Series
10, No. 59, 1970.
2. Cigarette smoking: United States, 1970, MVSR, Vol. 21, No. 3, Suppl. June 2, 1972, U. S. DHEW, PHS, HSMA, NCHS. 3. Gordon, T., and Kannel, W. B.: The Framingham, Massachusetts Study twenty years later, in Kessler, I. J., and Levin, M. L., editors: The Community as an Epidemiological Laboratory: A Casebook of Community Studies, Baltimore, 1970, Johns Hopkins Press, pp. 123-146. 4. Shurtleff, D.: Some characteristics related to the incidence of cardiovascular disease and death: Framingham Study, 1Syear follow-up, in Kannel, W. B., and Gordon, T., editors: The Framingham Study: An epidemiological investigation of cardiovascular disease, Section 30, U. S. Govt. Print. Off., 1974. 5. Gordon, T., and Shurtleff, D.: Means at each examination and interexamination variation of specified characteristics: Framingham Study, Exam. 1 to Exam. 10, in The Framingham Study: An epidemiological investigation of cardiovascular disease (Section 29). U. S. Govt. Printing Office, 1973. 6. Garvey, A. J., Bosse, R., and Seltzer, C. C.: Smoking, weight change and age, Arch. Env. Health Z&327, 1974. 7. Seltzer, C. C.: Effect of smoking on blood pressure, AM. HEART
J. 87:558,
1974.
September,
1975, Vol. 90, NO. 3
quitting
cigarette
smoking:
Tavia Gordon William B. Kannel, M.D. Thomas R. Dawber, M.D. Daniel McGee, M.S. Washington, DC, and Boston, Mass.
Since 1948, when the Framingham Study began, there has been a substantial change in cigarette smoking habits in the United States. One of its features-perhaps the most striking one-has been the substantial number of middle-aged men who have quit cigarette smoking.‘, * Presumably this has led to changes in medically related characteristics and in disease. The Framingham Study, which has had a general population under continuous observation during this period, provides an opportunity to assess the changes that have occurred.
The Framingham Study cohort when it first came under observation was 29 to 62 years old. The initial study population came from a sample of adults resident in the town of Framingham, Mass., and consisted of 5,209 men and women. They received a thorough standardized cardiovascular examination at entry which also elicited a large amount of information about their habits, their physical characteristics, their blood chemistry, and the like. Similar examinations were repeated every 2 years. This was supplemented by information on cardiovascular illness and death obtained from hospitals and other extra-clinic sources.3 From the Biometrics Research Branch, National Heart and Lung Institute, National Institutes of Health, Department of Health, Education and Welfare (Ms. Gordon and Dr. McGee); the Framingham Heart Disease Study, National Heart and Lung Institute, National Institutes of Health, Department of Health, Education, and Welfare, Washington, D.C. (Dr. Kannel); and Boston University Medical School, Boston, Maea. (Dr. Dawber). Received
for publication
Aug.
15, 1974.
Reprint requests to: Tavia Gordon, Supervisory Statistician, tries Research Branch, National Heart and Lung Institute, Institutes of Health, Bethesda, Md. 20014.
322
BiomeNational
Details with respect to laboratory methods and clinical criteria are available elsewhere.4 Histories of cigarette smoking were obtained on every examination except Exam. 6; however, information from the first three examinations was coded to represent usage at Exam. 1, leaving Exams. 2 and 3 uncoded. (More than half of those coded to Exam. 1 actually derived from Exam. 1, the bulk of the remainder from Exam. 2.) Unless otherwise specified, “smoking” means smoking cigarettes. In previous reports from the Framingham Study, “quitting” was defined retrospectively by a history of previous smoking habits obtained at entry to the study. Some data in that form are presented in this report but this is supplemented for the first time by information on people who were smoking when they first came under observation and who, while they were still under observation, quit smoking. Weight, blood pressure, vital capacity, drinking habits, and so on, were measured while they were still smoking and again after they quit. What happened concurrently to people smoking at entry who continued to smoke is also available from the routine re-examination of the cohort. Changes in characteristics are examined in two ways: (1) short-term changes occurring in the interval between the last examination while smoking and the following examination, that is, the first examination after quitting, and (2) longterm changes (between Exams. 4 and 10) for persons smoking at entry but quitting by Exam. 4. Age-specific means for the characteristics were calculated for the age groups 35 to 44, 45 to 54, and 55 years and over (age at Exam. 4). These means provided the basis for age-adjustment. Comparisons are made between those who quit and those continuing to smoke, with those not
September,
1975, Vol. 90, No. 3, pp, 322-328
Quitting
smoking:
Thp Frrrmingham
Stu&
I. Per cent smoking cigarettes by age and sex: Framingham Study, Exams. 1 and lO*
Table
All ages
61.0
37.1
40.2
31.0
29-33 34-37 38-41 42-45 46-49 50-53 54-57 58-62
62.8 71.5 67.2 58.0 56.1 58.9 43.6 48.3
43.8 48.0 45.2 32.4 29.9 32.1 18.8 18.6
51.1 56.6 48.8 38.0 28.1 28.7 23.4 15.0
43.0 48.5 37.2 29.8 20.0 18.7 12.4 6.0
ki y 20 i 1
- Men --Women
IO 1 01
*Persons must take both Exams. 1 and 10 to be included. Age is at Exam. 1 and defines age-specific cohorts followed for 18 years.
’
’
I
I
I
I
i
I
I
I
I
2
3 ‘53‘56
4 ‘54‘50
5 ’56s ‘60
6 ‘58‘62
7
0
9
IO
‘60‘64
‘62‘66
‘64‘68
l948-
‘53
I I. Per cent of men and women not smoking cigarettes after 18 years by original smoking status: Framingham Study*
‘?A-
‘54
‘66‘70
Exam
Table
Fig. 1. Per cent of men examination: Framingham
and women smoking cigarettes Study, Exams. 1 to 10.
Stop@
on
Smokbng
by foflorlng exam -
0 l-10 11-19 20 21-39 40+ *Includes
599 165 89 393 188 98
95.7 58.2 41.6 38.2 38.3 35.7
only persons who took Exam.
1226 417 139 208 41 18
97.0 39.3 18.0 13.5 14.6 5.6
10. -25
smoking at entry serving as a reference group. Statements of statistical significance are made at a 5 per cent level. It is, of course, difficult to decide when a person has quit smoking cigarettes and the criteria followed early in the study are not well defined. On later examinations, a person who had smoked for more than a year in the last 2 years was classified as a smoker, whatever his immediate smoking behavior. The relapse rate for those classified as quitting is low enough throughout the study to suggest that the criteria for quitting must always have excluded persons who were only beginning to try. Only about 20 per cent of the men who reported that they had quit at entry ever reported smoking cigarettes again, and nearly half of those who resumed smoking
American
Heart
Journal
-I5
-5 +5 +15 WEIGHT CHANOE On pcwdrl
+25
+35
+40
2. Weight change according to change in smoking habits in men under 65 years of age smoking cigarettes on examination: Framingham Study, Exams. 1 to 10. Fig.
smoked very little or only intermittently resumption.
after
Results Changes in smoking habits. Trends from 1948 to 1953, when the initial examination was performed, to the tenth biennial examination in 1966 to 1970 are shown for men and women in Fig. 1. Only persons taking both Exams. 1 and 10 are included. At entry 61 per cent of the men and 40 per cent of the women smoked cigarettes. Eighteen years later only 37 per cent of the men and 31 per cent of the women were still smoking.
323
Gordon
Table
et al.
III. Mean values of specified characteristics at entry by smoking status: Framingham Study* No. of cigarettes/day None Sex, characteristic
Men,
number
Age-adjusted
Women,
number
values
Never
Quit
Cigar, pipe
Total
803
277
215
311
1,498
138.1 87.8 381.2 17.4 172.9 5.3 224.0 83.4
138.4 87.5 382.4 10.0 173.4 5.2 222.0 84.1
137.8 87.4 382.4 20.7 171.7 5.3 230.5 82.7
138.0 88.3 379.4 21.7 173.2 5.2 221.3 83.2
1,634
1543
for the age groups
29-44,
45-54,
138.5 85.6 255.8 4.4 143.7 4.0 227.5 82.8 and
55-62
were
138.7 85.6 254.7 4.1 144.0 4.0 227.6 83.0 weighted
Decreases were fairly continuous during those 18 years, beginning as early as the second examination (1951 to 1954), with an accelerated rate of decline, especially apparent in men, beginning after Exam. 7 (1960 to 1964). Additional details of these changes are available elsewhere.” Table I compares the per cent smoking at Exam. 1 with the per cent smoking at Exam. 10. Decreases were observed for all age groups. By Exam. 10 men had dropped to about the Exam. 1 smoking levels of women. Women smokers were more persistent in retaining their original smoking habits, although even for them small decreaseswere observed for every age group. The more a person smoked at entry the less likely he was to be a nonsmoker 18 years later (Table II). Quit rates for women were lower than those for men in all smoking categories. So few Framingham women quit since the study began that their experience is not analyzed in this report. Characteristics by smoking habit at entry. At entry body weight varied according to smoking habit. For men the difference between cigarette smokers and nonsmokers was 8 pounds (Table
324
l-10
11-19
20
21-39
40+
254
139
608
314
183
91
136.1 85.4 371.4 27.5 164.7 5.0 228.5 82.4
138.1 86.8 372.4 23.4 165.0 5.2 225.4 81.6
133.9 83.5 372.3 18.3 160.5 4.9 226.1 82.9
134.8 84.9 373.7 24.1 162.9 5.0 228.6 82.5
136.8 85.6 372.5 30.7 166.4 5.1 229.6 81.6
138.1 86.7 359.6 45.8 170.2 5.2 232.5 83.8
1.174
580
182
313
75
24
133.9 83.5 264.0 8.4 139.4 4.0 226.9 82.0
134.4 82.3 263.6 11.0 133.2 4.0 235.4 81.2
134.7 83.4 262.2 11.6 138.1 4.0 234.1 79.9
131.5 83.7 260.6 17.7 139.2 4.5 240.8 80.9
154.9 92.5 244.8 19.6 144.4 4.3 209.8 77.4
mean values:
Systolic blood pressure (mm. Hg) Diastolic blood pressure (mm. Hg) Vital capacity (L.) Alcohol (oz./ma.) Weight (lb.) Uric acid (mg./lOO ml.) Serum cholesterol (mg./lOO ml.) Blood sugar (mg./lOO ml.) *Mean
Total
mean values:
Systolic blood pressure (mm. Hg) Diastolic blood pressure (mm. Hg) Vital capacity (L.) Alcohol (oz./ma.) Weight (lb.) Uric acid (mg./lOO ml.) Serum cholesterol (mg./lOO ml.) Blood sugar (mg./lOo ml.)
Age-adjclsted
Cigarette smoker
135.6 84.6 274.9 9.2 139.1 4.1 226.2 79.8 12122,
7122,
134.5 83.5 262.9 10.5 138.1 4.0 230.6 81.2 and
3122,
respectively,
to yield
age-adjusted
mean
values.
III). Nonsmokers include those who never smoked, those who had quit, and those smoking cigars or pipes. There is little difference in their weights. Smokers’ weights varied with the amount smoked, but no matter how many cigarettes were smoked per day, the average weight was less than that for nonsmokers. The leanest smokers were those smoking 11 to 19 cigarettes per day. Men smoking more than this weighed more, their weight being greater the more they smoked. Men smoking 40 or more cigarettes per day weighed nearly as much as nonsmokers. Data for women were very similar. Thus, while weight is clearly related to the fact of smoking and to the amount smoked, the association is nonlinear and therefore cannot be satisfactorily represented by a correlation coefficient or linear regression. In addition to weight only two other of the characteristics listed in Table III were found to differ between smokers and nonsmokers at entry-alcohol and vital capacity. Persons who never smoked used little alcohol, on the average, while men or women who smoked used more, the amount being greater the more cigarettes smoked. Vital capacity is lower among men smoking ciga-
September,
1975, Vol. 90, No. 3
Quitting
smoking:
Thr Frammgham
Studv
IV. Age-adjusted mean levels at entry of selected characteristics for cigarette smokers according to subsequent smoking history: Men, Framingham Study
Table
Mean Men smoking cigarettes/day
Characteristic Systolic blood pressure (mm. Hd Diastolic blood pressure (mm. Hg) Vital capacity (L.) Alcohol (oz./ma.) Weight (lb.) Uric acid (mg./lOQ ml.) Serum cholesterol (mg./ 100 ml.) Blood glucose (mg./lOO ml.) *Age-adjusted
means
are unweighted
l-10 at entry
Heart
Journal
at entry* Men smoking 20 cigarettes/day at en tT
Still smoking at Exam. 4
Not smoking at Exam. 4
Still smoking at Exam. 4
Not smoking ot Exam. 4
137.3
136.0
134.5
131.1
86.7
85.3
84.8
83.2
367.8 23.4 164.1 5.2 223.6
382.3 21.8 168.2 5.2 225.5
375.5 24.5 162.8 5.0 228.8
382.2 23.6 162.8 5.0 228.8
79.4
93.6
79.1
87.9
averages
of the
age-specific
means.
rettes than those not smoking. For women the difference in vital capacity is in the opposite direction. Both contrasts are statistically significant, if relatively small. Persons of either sex smoking 40 or more cigarettes per day have distinctly lower vital capacities than others, but few women smoked 40 or more cigarettes per day. Characteristics of men who later quit. Since so few women have quit smoking all the subsequent analysis is confined to men. It seemslikely that men who quit smoking are different from persons who continue smoking. What is not clear is whether the differences are such as to influence subsequent morbidity and mortality rates. Without a clinical trial involving randomization and the other usual safeguards of such trials it is impossible to conclusively resolve such an issue but it is possible to look at some relevant characteristics of smokers measured while they were still smoking and compare those smokers who subsequently quit with those who continued smoking (Table IV). Data are presented separately for men smoking one to 10 cigarettes per day and “exactly” 20 cigarettes per day at entry. These two groups account for the bulk of those subsequently quitting. When these comparisons are made only minor differences, in general, are noted. There were only trivial and not statistically significant differences between those who later quit and those who
American
level
continued smoking with respect to their entry levels for blood pressure, vital capacity, alcohol consumption, weight, uric acid, or serum cholesterol. There was one exception: Men who quit had a higher average blood glucose level before quitting than men who continued smoking. Most of the difference is accounted for by an excess number of diabetic subjects among smokers who quit smoking. This presumably indicates that ill health (in this instance, diabetes) is an incentive to stop smoking. Short-term changes after quitting. Under observation men under age 65 who quit smoking gained a small amount of weight immediately (3.8 pounds on the average) (Table V). If they were still not smoking at the next examination their weight remained fixed at the new level. (For this subgroup off cigarettes for two full examinations the average initial gain was 5.1 pounds followed by a trivial gain-O.3 pounds-in the next 2 years.) While there is a slight tendency toward weight gain (about half a pound) in men whose smoking habits remained unchanged from one examination to the next, this was, of course, significantly less than the weight increase for those who quit. Persons who resumed smoking lost about a pound after resumption. Illness, particularly the onset of clinical cardiovascular disease, may be a powerful incentive to stopping smoking and is also associated with weight changes. The average weight gain
325
Gordon
et al.
V. Changes in weight, systolic blood pressure, and serum cholesterol in smoking habits: Framingham Study, men under age 65 years*
Table
levels by change
Average change in characteristic Change in smoking habits from one exam. to next
No.?
Weight @.A
Serum cholesterol (mg./lOO ml.)
Smoking to nonsmoking Continued smoking
544 4,078
3.8 0.3
(2.3) (0.1)
1.6 0.7
0.2 -0.2
Nonsmoking to smoking Continued not smoking
246 3,120
-0.9 0.5
(-0.8) (0.1)
0.6 0.7
1.9 0.3
*Smoking histories are available at Exams. 1, 4, 5, 7, 8, 9, and 10. Only reports of current measurements on the same pair of examinations. The intervals are those between exams. tNumber of changes, not number of persons. $Parenthetical entries are for men free of cardiovascular disease on the first examination
after quitting is less if such persons are omitted, but the difference is trivial. The average difference in weight change between those who quit and those who continued smoking cigarettes is not accounted for by a few men with very large weight gains but arises from the fact that proportionately fewer among those who quit lost weight and more among them gained at least 10 pounds (Fig. 2). One would anticipate that the greater weight increase in smokers who quit relative to those continuing to smoke would be associated with relatively greater increases in blood pressure and serum cholesterol. In fact the difference in trends for these two characteristics is trivial and not statistically significant (Table V). Table VI considers changes for a number of characteristics in men who were smoking either one to 10 or 20 cigarettes per day at Exam. 1. These men are divided into two groups, according as they were or were not still smoking at Exam. 4. Short-term changes for those who quit are contrasted with short-term changes for those still smoking at Exam. 4 in the upper half of the table. These changes are compared with concurrent changes for those who continued to smoke. Both groups may be compared with those men who were not smoking at entry. For two characteristics-weight and vital capacity-men who quit smoking by Exam. 4 had statistically significant differences in trends from men still smoking at Exam. 4. The weight increase from Exams. 1 to 4 was greater for men who quit than for men who continued smoking, the difference being statistically significant for men smoking 20 cigarettes per day at entry.
326
Systolic blood pressure (mm. Hg)
smoking practices are considered, with smoking histories.
and
are compared
with
considered.
Men smoking 20 cigarettes per day who quit also had a statistically significant and substantially greater decrease in vital capacity between Exams. 1 and 4 than did those still smoking. This presumably implies that respiratory distress was one of the motives for quitting. Significant differences in short-term trends for those quitting and those continuing to smoke were not evident for alcohol consumption, uric acid, serum cholesterol, or blood sugar. Long-term changes after quitting. Long-term changes after quitting are shown for the 12 years between Exams. 4 and 10 in the lower half of Table VI. These may be contrasted with the initial short-term changes already discussed. There was a greater long-term decline in vital capacity for those who continued smoking than for those smoking the same amount who quit. For men smoking 20 cigarettes per day at entry the difference in trends was statistically significant. The long-term vital capacity trends of those who quit approached the concurrent experience of men who were not smoking at entry. Men who continued smoking had a greater long-term drop in serum cholesterol levels than those who quit but this difference was not statistically significant. Men who continued to smoke also had a slightly smaller long-term rise in blood pressure but, again, the difference was not statistically significant. After the initial weight changes, the long-term changes in weight for men who quit and men who continued to smoke cannot be distinguished. In brief, the only statistically significant difference in long-term trends among the variables considered is the greater drop in vital capacity for
September,
1975, Vol. 90, No. 3
Quitting
smoking:
‘The F’rrrrvinghnm
Study
VI. Change in smoking habits in men between Exams. 1 and 4 and concurrent and subsequent changes in certain other characteristics: Framingham Study ___~-.____
Table
f-10 cigarettes/day Characteristic Increase from Exams. 1 to 4: Systolic blood pressure (mm. Hg) Diastolic blood pressure (mm. Hg) Vital capacity (L.) Alcohol (oz./ma.) Weight (lb.) Uric acid (mg./lOO ml.) Serum cholesterol (mg./lOO ml.)$ Blood glucose (mg./lOO ml.)
Increase from Exams. 4 to 10: Systolic blood pressure (mm. Hg) Diastolic blood pressure (mm. Hg) Vital capacity (L.) Alcohol (oz./ml.)l( Weight (lb.) Uric acid (mg./lOO ml.) Serum cholesterol (mg./lOO ml.) Blood glucose (mg./lOO ml.)7
Not smoking at entry*
Quit at Exam. 4
-9.42
-0.22 3.43
-0.20
0.21
-2
(564)
(43) 10.12
7.66 -1.74
-1.72
-41.16 1.92
-40.47 3.27
-1.50 N.A. -7.47
10.39
*Adjusted to the age-distribution of men smoking l-10 cigarettes who quit and tAdjusted to the age-distribution of men smoking the same amount who quit. SParenthetical entries are the number of men in each group. §Exams. I and 4. IIExams. 4 and 7. llExams. 4 and 9.
While there is a considerable literature on the characteristics of men according to their smoking histories, there is very little information on what happened to men who quit smoking while under observation. Presumably such information is available in the files of various prospective studies but the subject seems to have excited little analytical interest. An exception is the Normative Aging Study which has recently published data on subjects measured 5 years apart. When the data for 214 continuing cigarette smokers are contrasted with data for 104 quitters the difference in weight gain was 4.2 poundsfi This is very similar to the Framingham findings. Findings with respect to blood pressure changes, however, differed somewhat.’ The Normative Aging Study reported continuing smokers had on the average no change in systolic blood pressure in 5 years but men who
American
Heart
Journal
Exam.
10.82 1.25 2.70 -0.06 7.53 1.97
(105) 7.57
139)
(348) 6.83 -0.92
-17.78 5.19 took
-1.88
6.43 x.54
N.A.
2.83
7.78 -0.29
(464) -1.79
12.18 0.77
7.57 1.20
-9.32
who
-0.16 -21.48 2.79
-0.07 -45.11
3.14 N.A.
(58) cl.97
-2.63
-0.20
5.32 70
20 cigar&es/dczy nt entry ..____~.-..~ ~. .-.. - - . ..._Quit at 1 Still smoking Exam. 4 ( at Exam. 4t I
-11.64 2.37 1.36
-0.31
6.38
Discussion
(152) -3.08
-18.63
2.07 2.53
men smoking 20 cigarettes per day at entry who continued to smoke.
Still smoking at Exam. 41
(51) -4.98 -3.04
(714)-J -4.00 -2.88
at entry
9.26 -0.79 -41.76 3.88 0.03 N.A. -5.48 2.16
-55.88 4.21 0.19
N.A. -12.27 7.66
4 (or IO).
quit had slightly higher systolic levels after quitting (3.6 mm. Hg). While this is a trivial difference and is probably of marginal statistical significance, it was noted that there was a greater blood pressure gain in each weight group among quitters than those continuing to smoke. The comparable data for Framingham would be those given in Table V for changes between Exams. 1 and 4. These show no difference in blood pressure trends for those who continued to smoke and those who quit despite a greater weight increase in those who quit. Unfortunately, strict comparability cannot be achieved, since the Normative Aging Study did not include men if their initial blood pressure was greater than l40/ 90 whereas there were no blood pressure exclusions in the Framingham Study. What is most striking in the Framingham data is how little difference there is between those who quit and those who continued smoking, either in their characteristics while still smoking or with respect to changes in these characteristics after stopping. Of the characteristics examined only
327
Gordon
et al.
two stand out-weight and vital capacity. A slightly greater short-term weight change and a smaller long-term decline in vital capacity among those who quit than among those who continued smoking were the chief findings. Only for men smoking more than 10 cigarettes per day were these differences statistically significant. No significant changes in blood pressure or serum cholesterol levels were found to be associated with quitting cigarette smoking. Information with respect to women smokers and with respect to men smoking more than a pack a day was too scanty for analysis, and it is conceivable that the effect of quitting is different in these groups than in the groups available for analysis. Men smoking a pack or less a day constitute the bulk of those who quit cigarette smoking and are consequently the group of major public health interest. In this group the impact of quitting on the major cardiovascular risk factors appears to be trivial so that the cardiovascular advantage of quitting cigarette smoking should be straightforward. Summary
During the first 18 years of the Framingham Study there was a substantial decrease (39 per cent) in the number of men smoking cigarettes and a moderate decrease (22 per cent) in the number of women smoking cigarettes. Except for a greater tendency of diabetic patients to quit smoking, there were no significant differences at
328
baseline between smokers who quit and smokers who continued smoking. After quitting there was a short-term rise in weight for men. This rise led only to trivial changes in blood pressure and serum cholesterol levels. There was a beneficial impact on long-term vital capacity trends from quitting smoking.
REFERENCES
1. Ahmed, P. I., and Gleeson, G. A.: Changes in cigarette smoking habits between 1955 and 1966, PHS Pub. No. 1000, Series
10, No. 59, 1970.
2. Cigarette smoking: United States, 1970, MVSR, Vol. 21, No. 3, Suppl. June 2, 1972, U. S. DHEW, PHS, HSMA, NCHS. 3. Gordon, T., and Kannel, W. B.: The Framingham, Massachusetts Study twenty years later, in Kessler, I. J., and Levin, M. L., editors: The Community as an Epidemiological Laboratory: A Casebook of Community Studies, Baltimore, 1970, Johns Hopkins Press, pp. 123-146. 4. Shurtleff, D.: Some characteristics related to the incidence of cardiovascular disease and death: Framingham Study, 1Syear follow-up, in Kannel, W. B., and Gordon, T., editors: The Framingham Study: An epidemiological investigation of cardiovascular disease, Section 30, U. S. Govt. Print. Off., 1974. 5. Gordon, T., and Shurtleff, D.: Means at each examination and interexamination variation of specified characteristics: Framingham Study, Exam. 1 to Exam. 10, in The Framingham Study: An epidemiological investigation of cardiovascular disease (Section 29). U. S. Govt. Printing Office, 1973. 6. Garvey, A. J., Bosse, R., and Seltzer, C. C.: Smoking, weight change and age, Arch. Env. Health Z&327, 1974. 7. Seltzer, C. C.: Effect of smoking on blood pressure, AM. HEART
J. 87:558,
1974.
September,
1975, Vol. 90, NO. 3
